ARTICLES

 

Mitigation and Adaptation Practices to the Impact of Climate Change on Wine Grape Production, with Special Reference to the South African Context

 

 

H. Theron^{I, *}; J.J. Hunted^II

^ICape Peninsula University of Technology (CPUT), Private Bag X8, Wellington, 7654, South Africa. ORCID ID: 0000-0003-2011-8244
^IIARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, South Africa. ORCID ID: 0000-0002-2711-5153

 

 

---

ABSTRACT

In South Africa, environmentally and socio-economically sustainable wine grape production is promoted by governmental and private initiatives. All the initiatives contribute to establishing a scientifically based response strategy of agro-systems to ensure sustainable production under future expected climate conditions. South African wine grape producers would probably have to cultivate their grapevines under higher atmospheric CO₂ levels and in warmer, mostly drier, conditions. Due to the projected increase in climatic variability, an effort must be made to improve the resilience of vines against these environmental conditions. Whole-vine functioning and balances should be considered when adjustments are made to current long and short term cultivation practices. All practices should be aimed at promoting the development of a deep, dense and buffered root system that is able to support a well-developed canopy with optimal microclimate that would sustain a high yield of good quality. Mitigation and adaptation strategies would most likely have to be region specific, and small scale terroir data, (which should include both climate and terrain/soil information) may play a critical role in decision-making.

Key words: Climate change, viticulture, grapevine, mitigation, adaptation, cultivation practices, sustainability

---

 

 

INTRODUCTION

The current concept of climate change does not refer to naturally occurring warming and cooling cycles over extremely long periods of time, but rather to "a change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and... is in addition to natural climate variability..." (UNFCCC, 2011). "Warming of the climate system is unequivocal,..., [with] many of the observed changes...unprecedented..." (IPCC, 2014). The increase in anthropogenic greenhouse gas (GHG) concentrations [expressed as carbon dioxide (CO₂) equivalents] is considered to be the main cause of global warming and is due to emissions of mostly CO₂, methane (CH₄) and nitrous oxide (N₂O) into the atmosphere (IPCC, 2014). Observation and monitoring systems, such as the Integrated Carbon Observation System (ICOS) in Helsinki and the Global Greenhouse Gas Reference Network (GGGRN) of the National Oceanic & Atmospheric Administration-Earth System Research Laboratories (NOAA-ESRL) in Colorado, make use of extensive air sample collection networks to determine the concentration levels of GHG. They use various analysing methods, such as gas chromatography for CH₄ and N₂O (ICOS, GML) and infrared absorption (GML) or gas chromatography (ICOS) for CO₂. Concentrations are then expressed as CO₂ equivalent units.

Higher atmospheric GHG levels increase the capture of radiated heat from the Earth (Mozell & Thach, 2014), causing warming of the air and land-ocean surface. Continued emission of GHG will result in further warming and a concomitant higher risk of causing irreversible damage to ecosystems and quality of life for humans. Indeed, certain facets of the climate system (such as ocean temperatures and acidification, sea level rise, soil carbon cycles, etc.) will continue to change for centuries to come, even if GHG emissions cease immediately (IPCC, 2014). Global mean surface temperature at the end of the 21^st century will thus be largely determined by the CO₂-equivalent units (CO₂-eq) that have already been emitted in the past.

The risks associated with climate change should be reduced as far as possible and managed in such a way that sustainable development, economic and social well-being, and effective natural resource and biodiversity conservation are ensured (IPCC, 2014). Adaptation and mitigation are the two types of action that could be taken against climate change (CCC, 2009). Adaptation is generally focused on how to remedy the current effects that the climate has on natural, biological and socio-economic environments. The impact of these practices is visible within a relatively short period of time. Mitigation is directed at the longer term and addresses the causes of climate change by attempting to reduce or eliminate sources of GHG emissions. These two strategies are complementary (IPCC, 2014) - adaptation can reduce the impact of climate change, but it will not be effective in the long term without supporting mitigating actions.

Any mitigation strategy aimed at the agro-system (farms and surrounding landscapes that provide the environmental, production, social and economic context) should focus on an integrated approach. It should combine measures to decrease energy use and net GHG emission; to decarbonise energy supply (fossil fuel) by replacing it with cleaner sources (biological, wind, solar); and to increase extraction and sequestration of CO₂ from the atmosphere (CAST, 2004). In any crop production system, there is a balance between carbon uptake from and its release back into the atmosphere. Plants take up carbon through photosynthesis and incorporate it as biomass during growth and yield production (CAST, 2004). Soils may also contribute to carbon sequestration in the agro-system, but the capacity would depend on factors such as the soil depth, nutrient and clay content, water holding capacity and the susceptibility of the soil to erosion and mineralisation (Lal, 2018). Carbon is mainly emitted back into the atmosphere due to soil respiration, which is the respiration of the plant roots and soil micro-organisms combined (CAST, 2004). In well-established agro-systems, cultivation practices should be focused on the hoarding and emission of carbon. Firstly, the size of the carbon sink should be increased (IPCC, 2014; Tubiello et al., 2014). This may be achieved by the cultivation of perennial grass crops where possible (CAST, 2004) or by establishing cover crops in working rows of vineyards (Tezza et al., 2019) and orchards. Secondly, cultivation practices should decrease the amount of carbon emission (CAST, 2004). This may be obtained by limiting soil cultivation and thereby protecting the soil against unnecessary degradation and mineralisation (Lal, 20218) which would detrimentally affect the water and nutrient holding capacity of the soil. Maintaining natural vegetation between production units where still possible (Tezza et al., 2019), restoring highly degraded land and wetland to their natural vegetation, and avoiding unnecessary conversion of natural vegetation areas for agricultural production where it is not economically viable, would also increase the carbon sequestration potential of the agro-system.

The expected increase in both water demand and its scarcity will force the agricultural sector, which is currently accountable for 70 % of global freshwater use (IPCC, 2019), to improve water retention in the soil, adapt irrigation strategies to limit water use and consider alternative water sources, such as recycled wastewater for irrigation. Climate Smart Agriculture (CSA) is one such approach aimed at "securing sustainability and resilience [of production systems] while providing economic, ecological and social benefits" (WCG, 2015).

In South Africa, the Smart Agriculture for Climate Resilience (SmartAgri) project commenced in 2014 with the purpose of developing "a practical and relevant climate change response framework and implementation plan specifically for the agricultural sector of the Western Cape" (WCG, 2014). This project is directed by the African Climate and Development Initiative (ACDI) of the University of Cape Town in collaboration with the Western Cape Department of Agriculture, the Western Cape Department of Environmental Affairs and Development and the Agricultural Sector. In May 2016, the SmartAgri climate change response strategy and action plan was launched. Six priorities (conservation agriculture; restoring degraded landscapes; improved catchment management for water security and job creation; energy efficiency; "climate-proofing" the Western Cape's agri-processing sector and integrated knowledge system for climate smart practices) were highlighted to be focused on by both government and industry (WCG, 2016). Recent studies confirmed the critical role that human decisions can play in improving the resilience of the agricultural sector to climate change (Morales-Castilla et al., 2020).

This manuscript has two focus areas. The first comprises climate change within the context of the South African wine industry. The second discusses challenges faced by the South African wine industry and possible adaptation and mitigation strategies that may be applied during the production of wine grapes, with reference to the concept of "terroir".

Climate and Wine Grape Production

Since the grapevine is indigenous to the Mediterranean region and was mostly cultivated over narrow climatic and geographical ranges (mid-latitude regions) it was originally thought to be sensitive to changes in climate (Jones & Webb, 2010). However, new wine regions in tropical and meso-tropical climates started to emerge (Mira de Orduña, 2010) and currently, grapevines are cultivated on six of the seven continents across a wide climatic range (Schultz, 2016). It is clear that the grapevine has in fact a natural ability to adapt to the environmental conditions in which it is grown. Due to this eco-physiological adaptation capacity (plasticity) of the grapevine, it is not sufficient to use only bioclimatic indices when evaluating a region for quality wine production (Schultz, 2011; Seguin & Garcia de Cortazar, 2015). Furthermore, the large physiological and morphological differences between grape cultivars allow successful wine grape production over a wide range of climates (Anderson et al., 2008; Keller, 2010). However, for every region, there are climate limits outside which viticulture will cease to be sustainable (Morales-Castilla et al., 2020; Santos et al., 2020).

Climate models are often used to determine the suitability of a region for a specific purpose, such as wine grape production. Average temperature as a single factor is commonly used (Webb et al., 2007; Hall & Jones, 2009; Hannah et al., 2013), but temperature models are not able to discern between regions based on climate variability (Hunter & Bonnardot, 2011). Another option is to integrate climatic factors within one model, as was done by Webb et al. (2013) with temperature and precipitation, but this is also insufficient should the total effect of the complete climate system on wine production be the objective. Regions with similar mean temperature and precipitation may differ significantly in terms of the timing and frequency of the precipitation, the diurnal temperature range or the occurrence of extreme climatic events.

Hunter and Bonnardot (2011) combined temperature and potential photosynthetic activity to quantify the impact that temperature may have on grapevine physiological behaviour at specific locations. They concluded that the use of mean climatic indices is not sufficiently discriminatory and may lead to the zoning of only apparently homogeneous terroirs. It is therefore necessary to assess climatic suitability of a region at fine scale (regarding time and space) to better determine the potential for grapevine growing at a specific location/terroir, especially in regions with a complex terrain (Hunter & Bonnardot, 2011; Quenol et al., 2017; Sturman et al., 2017). Fraga et al., (2016) coupled dynamic crop models, which simulate plant growth and development, with high-resolution climate simulations to generate future projections of yield, phenology and possible stress indicators for grapevines. Even sophisticated methods such as these have their limitations, since certain assumptions and generalisations are always required in the programming (Fraga et al., 2016). Other factors, such as air relative humidity and wind speed that affect evapotranspiration, are often omitted (Bois, 2019), thereby decreasing the accuracy of model-based predictions.

The application value of any model is dependent on the resolution level and accuracy of the data available. In the Western Cape of South Africa, actively logging weather stations are currently still sparsely distributed and producers in the agriculture sector have limited access to high resolution climate data. A study was done to investigate the possibility of using remote sensing data of mean land surface areas as alternative technology to supplement weather station data (Southey, 2017). The strong linear relationship found between remote sensing data and weather station data indicated that the former could be used for temperature estimates where weather stations are not yet present.

The Western Cape has a very complex topography. There is large variation in elevation (Fig. 1), slope gradients and aspects as well as a long coastline with various degrees of exposure to the sea breeze effects from both the Indian and Atlantic oceans, which is intensified by the cold Benguela current of the latter (Carey, 2001; Hunter & Myburgh, 2001; Bonnardot et al., 2002). There is also significant variation in soil type regarding texture, depth and water and nutrient holding capacity (Hunter & Myburgh, 2001). All of these result in a variety of meso climates within very short distances (Hunter & Bonnardot, 2011; WCG, 2015; Midgley et al., 2016) that often require small scale (spatial) adaptation of agricultural practices to accommodate the specific local growth conditions. Integrated online platforms already exist that provide detailed information to the agricultural sector on climate, terrain and soils to better understand the topographical and climatic complexity of the Western Cape as a region, but also down to farm and vineyard block level (Southey, 2021).

The South African Context

The production of wine grapes, as with any agricultural crop, is strongly dependent on natural resources. Initiatives to encourage environmentally and socio-economically sustainable grape and wine production are becoming an increasingly integral part of both production and marketing. Sustainable Wine South Africa (SWSA, n.d.) is an alliance between the Wine of Origin (WO) and Integrated Production of Wine (IPW) schemes of the Wine and Spirits Board (WSB). A certification seal was implemented in 2010 that was the first of its kind in the world (Fig. 2). Producers must prove compliancy with set regulations in order to qualify for certification. This seal serves as guarantee of integrity and sustainability. "Integrity" confirms the origin (100 % of content), vintage (at least 85 % of content) and cultivar(s) (at least 85 % of content) information on the bottle label. "Sustainability" declares that the grapes were produced and the wine was made according to strict environmental guidelines (originally drafted in 1998 and updated annually), while biodiversity was protected and waste water treated.

 

 

The Confronting Climate Change (CCC) Initiative is linked with sustainable agriculture and was originally conceptualised by the South African fruit and wine industries in 2008. The aim of this project is to support these industries in determining their current GHG emissions and developing solutions to mitigate the impacts of climate change (CCC, n.d.). In the unpublished report of 2019 that focused on wine grape production in South Africa, it was stated (based on combined data from 2011-2018) that wine grape production emits 3-4 t CO₂-eq/ha (gross value) into the atmosphere. This is relatively low compared to table grapes (9-10 t CO₂-eq/ha), stone and pome fruit (9 t CO₂-eq/ha) and citrus (7 t CO₂-eq/ha) (CCC, 2019). These values were obtained from normalised, graded data from the current database, which represents less than 10 % of the wine industry (in hectares) (A. Blignaut, personal communication, 2019). However, when expressed as kg CO₂/kg fruit produced, the emission was higher for wine grapes (0.41) than for pome fruit, stone fruit or citrus (Fig. 3), because of the relative lower yield per hectare of wine grapes (A. Blignaut, personal communication, 2019).

 

 

The three main contributors to GHG emissions on wine grape farms are electricity (46 % to 48 %), fuel consumption (28 %) and the use of fertilisers (20 %) (Fig. 4). The electricity use is primarily related to irrigation, while fuel consumption comprises all traffic during the production process (spraying of pesticides and herbicides, fertilisation, pruning, harvesting, etc.). Emission values would most probably differ between regions, cultivars used, and the type and efficiency of cultivation practices, but due to the small representing sample it is difficult to make deductions. However, it is clear that these three aspects should receive special attention when developing strategies to decrease GHG emissions on any farm. Greenhouse gas emissions as a result of the winemaking process is calculated separately and does not form part of this data.

 

 

South Africa is the 7^th (2020) largest wine producing country (by volume) in the world, with a production of 1040 million litres of which 65 % is white and 35 % red (SAWIS, 2020). About 35 % of the total volume of wine produced is exported, with the majority being in bulk. However, bulk wine decreased consistently over the last years, from 66 % of exported volume in 2013 to 59.8 % in 2018 (SAWIS, 2018) and 57.1 % in 2020 (SAWIS, 2020). Reasons for this trend may partially be ascribed to the better performance of packaged wines and the EU Trade Agreement that increased the duty-free quota for South African wines from 50 to 110 million litres per year (DKC, 2015; SAWIS, 2015). The five largest international markets (per volume) for South African wines are the United Kingdom, Germany, Netherlands, USA and Sweden (SAWIS, 2020).

There are 2693 primary wine grape producers in South Africa of which 74 % produce less than 500 tons of grapes per year (Table 1) (SAWIS, 2020). Only five producers harvest more than 10 000 tons of grapes per year. The 529 wine cellars comprise of 457 private wine cellars, 45 producer cellars and 27 wine producing wholesalers. The smaller wine producers are in the majority, with 70 % of the cellars crushing 500 tons of grapes or less per vintage.

 

 

A variety of cultivars are planted, but 82 % of all the vineyards in South Africa comprise of eight cultivars -Chenin blanc, Colombar, Cabernet Sauvignon, Sauvignon blanc, Shiraz, Pinotage, Chardonnay and Merlot noir (Fig. 5) (SAWIS, 2020). In total, there are 92 005 hectares of wine grape vineyards, 55.4 % planted with white cultivars and 44.6 % with red.

Ten geographical units are demarcated under the Wine of Origin scheme of which the Western Cape is the largest, comprising of five regions - Breede River Valley, Cape South Coast, Coastal Region, Klein Karoo and Olifants River (WOSA, 2021). The wine industry accounted for 1.1 % of South Africa's GDP in 2019 and contributed R55 billion to the economy - 56 % of which originated in the Western Cape (FTI, 2021). A further amount of R7.2 billion was generated through tourism. The South African wine industry provides 269 096 employment opportunities over the entire value chain (the majority being classified as either unskilled or semi-skilled) of which 36 406 are in the tourism industry (FTI, 2021) and 62 % employed in the Western Cape. The latter province is thus clearly a critical role player in the South African wine industry.

The Concept of Terroir

The OIV resolution (OIV/VITI 333/2010) defines the viti-vinicultural terroir as "a concept which refers to an area in which collective knowledge of the interactions between the identifiable physical and biological environment and applied viti-vinicultural practices develops, providing distinctive characteristics for the products originating from this area". Three important aspects may be extracted from this definition:

- interaction between the physical and biological environment

- applied viti-vinicultural practices

- a distinctive product character

Interaction between the physical and biological environment

This interaction refers to the optimization over time of the physiological activity of the grapevine (scion-rootstock genotype) under the site-specific growth conditions in order to produce satisfactory grape quality and to ensure economic sustainability. The better the fit between the physical environment (climate and soil) and the grapevine, the less intervention through cultivation/management practices is required and the higher the expected grape quality. This reduces input costs and increases profitability while limiting detrimental effects to the environment.

An integrated research approach is required with multi-disciplinary focus areas. Improved and expanded knowledge on eco-physiological mechanisms in the plant in response to all environmental factors and cultivation practices seems crucial (Schultz, 2011; Martinez-Luscher et al., 2015), while it should ideally be combined with molecular, genetic, anatomical, and plant physiological studies (Schultz & Stoll, 2010).

Over the last few decades, in accordance with prediction models, the average temperature during the grapevine growing season has increased in most of the global wine producing regions. This warming was not uniform, with higher warming rates in the Northern than in the Southern Hemisphere and a higher increase at higher than at lower latitudes (Jones et al., 2005; Webb et al., 2013). Using long-term climate data over the last four decades, Southey (2017) found a warming trend in the Western Cape, especially during the spring and summer months (September to March), with the interesting exception of September that had a cooling trend. This increase in average temperature was mostly due to the increase in maximum temperature (1 ^oC to 2 ^oC), rather than the increase in minimum temperature (0.6 ^oC to 1 ^oC). Should this trend continue, grapevines will grow and grapes will ripen under gradually warmer conditions, albeit with higher day-night temperature amplitude, in South Africa. However, clear spatial differences were found, which again indicate the need for fine scale demarcation in climate and terroir research.

Higher average winter temperatures were also reported for the months between April and July (Southey, 2017). This may have a negative effect on dormancy and bud break, since exposure to low temperatures during endodormancy increased both the budding rate and percentage (Dokoozlian, 1999; Pérez & Rubio, 2021). Increasing temperatures during spring, when buds are in the ecodormancy phase, stimulate bud break (Pérez & Rubio, 2021). The combination of higher winter temperatures and lower early spring (September) temperatures in the Western Cape may thus increase the occurrence of uneven and delayed budding and initial shoot growth. Although there is no direct link between the time of flowering and the onset of grape ripening (véraison) (Vondras et al., 2016), a high degree of asynchronous flowering may result in an uneven onset of véraison of the berries, which may cause uneven berry size and ripening. The effect of uneven berry ripening is often mitigated in the vineyard by harvesting the grapes later at a higher ripeness level (Gray & Coombe, 2009; Barbagallo et al., 2011), causing a shift in the aroma and volatile profile of the wine (Hunter et al., 2014; Terblanche, 2019).

The expected temperature increase during berry ripening could be to the advantage of current cooler regions (Cabré & Nuñez, 2020), where warming may increase growth and improve grape and wine quality, as found in the Mosel and Rhine Valleys in Germany (Jones et al., 2005). Although higher temperatures may further enhance growth and yield in warmer regions (should water be available), the quality may decrease due to unbalanced ripening profiles and fruit composition (Van Leeuwen et al., 2008). Fraga et al., (2016) reported an altered wine style under higher ripening temperatures. However, it is possible that the higher temperatures may exceed the optimum levels for specific cultivars within certain regions (Jones et al., 2005; Cabré & Nuñez, 2020). This may force a change in cultivar choice.

Expected changes in the rainfall (and other forms of precipitation) patterns are not as reliable as those of temperature, but generally climatic models indicate a wetter climate for higher latitude countries and regions (such as New Zealand, the Mosel Valley and the north of Oregon) and a drier climate for Southern Europe, Australia and South Africa (Webb et al., 2013). The reliability of the rainfall will also be less with regards to amount, intensity, timing, geographical distribution and annual variability (Wooldridge, 2007). Based on Global Circulation Models and downscaled rainfall projections, the Western Cape should expect a decrease in winter rainfall over most of the province (Midgley et al., 2016) and a shorter core-season (Midgley et al., 2005). However, the complex topography contributes to the high level of uncertainty reported at regional level, due to the possible increase in orographic rainfall during spring and autumn on windward slopes (Midgley et al., 2016). Long-term data seem to suggest that the timing of winter rainfall is moving to late winter and early spring (Southey, 2017), albeit with high levels of variability.

Water availability is considered to be the most limiting factor for agricultural production in South Africa (Benhin, 2006). The Western Cape has experienced water shortages over the last decade, with strong (and increasing) competition between the agricultural industry, urbanised regions and environmental reserves (Schulze, 2016). Although the Western Cape is the province with the most registered dams in South Africa (1592 out of 5592 - RSA, 2019), the majority are small and mainly used for irrigation (Midgley et al., 2016). Sufficient water storage capacity will always be a critically important factor, especially within the context of climate change. Montmasson-Clair & Zwane (2016) found that South Africa is currently underprepared for the occurrence of future droughts.

The water requirement of vineyards (300-700 mm) is higher than the annual mean precipitation in many winegrowing regions (Medrano et al., 2015a). In most of the viticulture regions of South Africa, the amount of precipitation is not sufficient to meet the water demands of the grapevine (Hunter & Myburgh, 2001). According to Van Zyl and Van Huyssteen (1980), producing grapevines cultivated in the coastal region of the Western Cape require approximately 500 mm of water between September and April of which an average of 300 mm is normally contributed by rainfall. The grapevine industry therefore depends strongly on irrigation during the dry summer months - for instance, in the Berg River catchment area, almost 90 % of all agricultural irrigation water is allocated to table and wine grape cultivation (Midgley et al., 2016).

The combination of higher environmental temperature and limited available water may accelerate soil salination in the root zone of the grapevine, either due to increased evapotranspiration (Wooldridge, 2007; Keller, 2010), or to the lack of good quality irrigation water (Anderson et al., 2008). This may result in wines being described as "brackish", "seawater like" or "soapy" (Mira de Orduña, 2010). Higher evapotranspiration may also increase water stress in the vines, which may have a negative impact on yield (Fraga et al., 2016).

Atmospheric CO₂ continues to rise, with current levels at 416 ppm (NOAA-ESRL, 2021) compared to about 340 ppm in 1980. This is considered to be the main cause of warming (IPCC, 2014) and increased CO₂, together with increased temperature, would therefore be an inseparable combination in future climates. When combined with the expected decrease in water availability, it is clear why multi-factorial research on the interactive effect of these climate factors on plant response (growth and physiological functioning) was identified as an important and unavoidable objective (Hunter et al., 2010; Salazar-Parra et al., 2012; Zinta et al., 2018) to meet the global challenge of climate change for the wine industry of the future (Schultz & Stoll, 2010).

There are more factors to consider in the physical environment than CO₂, temperature and water availability. Soil is one of the two main factors (the other being climate) that support high quality wine production (Leibar et al., 2015). The location of a specific soil will also determine its characteristics. Mountainous sites are considered to be sensitive to climate change (Caffarra & Eccel, 2011) with cooler soils that dry out faster (Hunter & Myburgh, 2001) than soils situated in lower lying regions. Higher soil temperatures will cause increased rates of nitrogen mineralisation (Schultz, 2016), with concomitant soil degradation and structure decline. Soil management strategies to sustain soil structure and improve its water and nutrient holding capacity are critical due to the direct impact on plant water status, vine functioning and eventual grape composition (Van Leeuwen & Destrac-Irvine, 2017). Increased effective soil depth, improved water holding capacity and good drainage will enhance deep root penetration that would help to buffer grapevines more effectively against adverse climate conditions and sustain the production of good quality grapes.

Due to changed migration patterns, the occurrence of pests and diseases is increasing in areas that were previously considered too cool, and therefore uninhabitable (Tate, 2001; Anderson et al., 2008; Mira de Orduña, 2010). The biggest challenges with regard to crop protection are the higher survival rate of pests and diseases during the warmer winters, and the afore-mentioned change in species within a specific region (Santos et al., 2020). Climate change may therefore also affect crop protection practices, which may have to be adapted at regional level.

Applied viti-vinicultural practices

Even before the relatively new concept of "climate change" was introduced, producers used to adapt their cultivation practices according to the prevailing climatic conditions to consistently produce a good quality product (Clingeleffer, 2010; Hunter et al., 2010; Neethling et al., 2013). However, short-term adaptation strategies (that could be executed within one growing season) may serve as protection against specific threats (Santos et al., 2020), but will be less effective in regions already close to temperature limits for grapevine cultivation (Morales-Castilla et al., 2020).

Over the last few decades, phenological events shifted backwards due to the changing climate, with earlier bud break, flowering, véraison and harvest, especially in cooler wine producing regions (Koch & Oehl, 2018). Shorter time intervals between phenological stages (Jones & Davis, 2000) were generally noted, which may translate into smaller optimum harvest windows for quality wines (Jones, 2007) and a compression of harvest dates (Anderson et al., 2008). Grape ripening now tends to occur during the warmer and drier months in summer (Mozell & Thach, 2014; Fraga et al., 2016), with higher respiration rates resulting in accelerated ripening with higher sugar concentrations (among other things also due to higher transpirational water loss from berries); a lack of phenolic and flavour expression; lower acid levels; higher pH, and an overall unbalanced juice composition (Jones 2007; Van Leeuwen et al., 2008; Keller, 2010; Mira de Orduña, 2010; Koch & Oehl, 2018). Adaptation of cultivation practices may delay berry ripening and ensure that it still occurs during the milder temperatures later in the growth season (Van Leeuwen et al., 2019). Although the importance of delayed ripening per se is relative to the context of the region (and not that relevant in South Africa compared to certain regions in the Northern Hemisphere), related recommendations may be considered locally to manage or extend the harvesting window and prevent logistical problems at the cellar due to compressed ripening. Late pruning in warm areas may delay harvest by postponing the onset and decrease the rate of ripening (Moran et al., 2019), while lighter pruning may also serve to delay véraison and harvest (Clingeleffer, 2010; Zheng et al., 2016; Van Leeuwen et al., 2019) by increasing the reproductive:vegetative growth balance. However, this type of intervention requires serious circumspection. Although it may cause delayed fruit ripening, a too high reproductive:vegetative balance (overcropping) may result in impaired berry set and smaller berries (Weaver & Pool, 1968), while colour development in the grapes and reserve accumulation in the vine may be deleteriously affected (Weaver & Mccune, 1960; Weaver & Pool, 1968). In the long term, weaker vines with lower yield potential may be the likely result (Weaver & Mccune, 1960).

Since the impact of climate change is highly heterogeneous across cultivars, regions and even vineyards (Jones et al., 2005; Fraga et al., 2016), effects on viticulture will depend on the cultivar/rootstock combination and the cultivation strategies followed within a specific terroir. In order to protect the grapevine against detrimental effects caused by climate change and to improve its resilience, a total cultivation strategy should be adopted regarding both long term practices (starting with site selection and soil preparation) and short term seasonal practices (Hunter et al., 2010).

Site and cultivar/rootstock selection Climate models are often used in combination with crop models to generate future projections of yield, phenology and possible stress indicators for grapevines. Especially in regions with a complex terrain (Hunter & Bonnardot, 2011; Quénol et al., 2017; Sturman et al., 2017), the assessments should be done on a fine scale (regarding time and space) to better reflect the specific terroir. Neethling et al., (2013) conducted interviews with producers in the Loire Valley in France regarding their adaptive response to climate variability. The physical characteristics of a vineyard site very often caused producers to adapt their standard cultivation practices in a vineyard. is. Thus, there is a need for real-time, accurate information available to producers on local conditions to aid decision-making.

Where changes in climate are relatively gradual, grape growers may prefer (with due reason) to rather adapt cultivation practices of an existing vineyard than incurring the cost of replacing/re-grafting vineyards (Morales-Castilla et al., 2020). However, in regions where climate change is considered to be of more eminent threat, conditions might necessitate the re-establishment of vineyards with different cultivars known to the growers or even with cultivars that are not traditionally planted in the specific region. Due to the lifespan of plantings and the cost involved in vineyard replacement (Schwab & Maass, 2010; Edwards et al., 2017), a timely cost analysis (on vineyard and winery level) is advised (Mozell & Thach, 2014) to determine whether only cultivar replacement is required or whether the cultivation of other crops should be considered (Bonfante et al., 2010).

Regional changes in cultivar spectra are already occurring (Koch & Oehl, 2018) and it may be expected that lesser-known cultivars better suited to the regional environment (current and predicted) would increasingly be established (Keller, 2010). More than 4000 wine grape cultivars were listed by the OIV in 2013 (OIV, 2013), which indicate the large genetic variability and plasticity of the grapevine genome (Medrano et al., 2015a; Bota et al., 2016). These cultivars should be evaluated under regional conditions to select new possibilities based on ideal traits, such as adaptability to variable climate conditions (Clingeleffer, 2010); balanced fruit:leaf area ratio and optimal berry composition (specifically colour and flavour) when ripening under high temperatures (Clingeleffer et al., 2013); late season ripening to extend the harvest (Van Leeuwen et al., 2008; Duchene et al., 2010; Schwab & Maass, 2010); and efficient physiological use of water (WUE), particularly under conditions of water stress (Clingeleffer et al., 2013; Bota et al., 2016).

A change in cultivars might be compelled by climate change, but is prohibited in certain wine producing countries (e.g. France, Italy and Germany) by legislation and tradition where only approved cultivars may be established according to the regional cultivar/quality classification (Webb et al., 2013; Morales-Castilla et al., 2020). In countries where such legislation does not exist, such as South Africa, Australia, the USA, China, etc. cultivar replacement should pose fewer problems.

The sensitivity of the scion cultivar to climate change may be reduced by the rootstock choice (Southey, 1992). Under such circumstances, the most important characteristics for rootstocks seem to be moderate vigour (Clingeleffer, 2010); tolerance to soil salinity (Keller, 2010) and tolerance to low soil water conditions and drought (Serra et al., 2014; Hunter et al., 2016; Simonneau et al., 2017; Peccoux et al., 2018). The rootstock may also affect the phenology of the scion and could possibly be used to manage and control the time of ripening (Van Leeuwen et al., 2019).

Modification of the grapevine genotype to incorporate desirable traits is possible, but its practical application is prevented by policies and legislation (Anderson et al., 2008). In the long term, genetic improvement of cultivars (scion and rootstock) is one of the better strategies to support sustainable wine production systems (Torregrosa et al., 2017) and it could be advantageous for wine industries to invest in breeding programmes (Jones, 2010), despite it being slow and expensive (Bota et al., 2016).

Soil preparation

Good soil management practices should prevent soil degradation and erosion, while improving physical, chemical and biological properties. Excessive tillage would cause soil degradation (Keller, 2010; IPCC, 2019), negatively affect most soil microbes and their activity (Santos et al., 2020), and increase evaporation from the soil (Schultz, 2000). Clean cultivation would increase soil erosion and CO₂ release from enhanced breakdown of organic matter where increased precipitation intensities are expected (Schultz & Stoll, 2010). Evaporation and the risk for erosion may be decreased by covering the soil surface with straw or organic mulch (Keller, 2010; Medrano et al., 2015a; Santos et al., 2020). According to Blanco-Canqui et al., (2015), cover crops improve soil structure, water infiltration and retention, moderate soil temperature (more optimum conditions for grapevine root growth), increase biodiversity and microbial properties, recycle nutrients and suppress the growth of weeds. Cover crops also contribute to CO₂ extraction from the atmosphere and the carbon sequestration potential of the agro-system (Tezza et al., 2019). It is generally advised that vineyard soils are covered by green vegetation during the rainy season (Santos et al., 2020), while care should be taken in arid and semi-arid regions to avoid excessive vine stress due to competition with the cover crops for water and nutrients (Schultz & Stoll, 2010).

Root growth and distribution are largely affected by physical (Van Huyssteen, 1988) and chemical (Conradie, 1988) soil properties and it is therefore critical that any potential limitations to root penetration and distribution are eliminated during soil preparation. Above-ground growth as well as root growth were improved by deeper soil preparation (Conradie et al., 1996). Since these effects were more pronounced in dryland vineyards, it was deduced that the deeper penetrating roots were able to exploit the available soil volume better for the uptake of water and nutrients (Van Huyssteen, 1988).

Planting of new vines

During the first season after planting, strict weed and pest control should be applied and water stress of the young vines avoided (Creasy & Creasy, 2009; Jackson, 2014). Young grapevines are generally well-supplied with water and nutrients (especially nitrogen) to maximise vegetative growth (Myburgh et al., 1996) in an attempt to reap a harvest already in the second season (Keller, 2005). The latter is not advisable, since it may have a negative impact on longevity of the vine. The promotion of shoot growth in the young vines will ensure strong root growth due to the positive relationship between aerial and subterranean growth (Hunter & Volschenk, 2001; Archer & Hunter, 2005, 2010). Canopy growth depends on the root system for the provision of water, minerals and hormones, while a good canopy development and micro climate would enhance root growth through the supply of carbohydrates, amino acids and hormones. A well-developed root system, in combination with judicious management practices, would buffer the vine against adverse climate conditions or environmental stress for the rest of its productive life (Archer & Hunter, 2010).

Vine training, spacing, row orientation, trellising and canopy management

The higher expected vigour in future climatic conditions (where water supply is not limited) may necessitate adjustments in vine training and trellising systems. In South Africa, where high vigour in warmer regions has been the norm for many years, it was found that higher trellis systems (bunch zone further away from the soil surface) improve the micro climate inside canopies by decreasing the average leaf and bunch temperature (Zeeman, 1981). On the other hand, shorter grapevine trunks (as obtained by the Guyot or goblet systems) may promote water use efficiency in the vine (Santos et al., 2020) and improve drought resistance (Van Leeuwen et al., 2019), probably due to the smaller vine size. However, this may be over-simplified, since higher evaporation rates from goblet vines than vines trained onto larger training systems have been measured, due to higher ambient air temperature and air movement in the canopies (Van Zyl & Van Huyssteen, 1980).

A good understanding and application of the inherent balance between shoot and root growth and between vegetative and reproductive growth (Hunter & Volschenk, 2001; Archer & Hunter, 2005, 2010) will increasingly be required to manage vineyard vigour and to translate that into sustainable yield and quality. Young vine training, the choice of vine spacing (Archer et al., 1988; Hunter 1998a, 1998b), the type and size of trellising system and thus the perennial structure of the vine (Hunter & Volschenk, 2001) as well as the orientation of vineyard rows (Hunter et al., 2010, 2016, 2017) are all tools for the producer to optimise the canopy micro climate (radiation, air flow, temperature) in which the leaves photosynthesise and the bunches ripen.

The extent and timing of canopy management practices directly affect microclimatic conditions and thus eventual grape quality (Hunter, 2000; Hunter & Volschenk, 2001; Volschenk & Hunter, 2001; Hunter et al., 2004). Any change in micro climate would alter energy dynamics within the canopy and inside the vine itself, which would affect grape ripening, composition and the eventual wine style (Hunter et al., 2010). Management neglect or injudicious execution of cultivation practices may lead to under-utilisation of the site potential (also determined by soil, climate, and scion-rootstock genotype) for grape growing and wine quality (Hunter & Bonnardot, 2011; Hunter et al., 2011).

Irrigation and fertilisation

Water scarcity is expected to become one of the main challenges in many viticultural areas and it is therefore important to improve the water use efficiency of the vine for long term sustainability (Salazar-Parra et al., 2012; Mozell & Thach, 2014; Fraga et al., 2016). The amount of water required per irrigation depends on many factors, such as the soil texture (a lower frequency with larger volume per irrigation is advisable for compact, silty, clayey and general duplex soils), seasonal climatic conditions, the scion-rootstock combination, vigour of the growth, and viticulture practices (Hunter & Myburgh, 2001). The correct type of irrigation system may increase water supply efficiency and thereby the saving of water (Van Zyl & Van Huyssteen, 1988). Alternative sources of irrigation water (such as wastewater from wineries) may also be cautiously considered in order to reduce the impact of grapevine cultivation on natural water resources (Myburgh & Howell, 2014). Such water sources should be tested very well before large-scale applications are considered. Judicious deficit irrigation increases the water use efficiency (WUE) of the vineyard (Clingeleffer, 2010) while simultaneously saving water. The success of deficit irrigation practices is strongly dependent on the interaction between the genotypes (scion cultivar/rootstock) and the environment in which it is grown (Medrano et al., 2015a).

Conradie et al., (1996) found (on a granitic Glenrosa soil in the Stellenbosch area) that soil-derived N is sufficient to supply the required N of the vine for the first three years after soil preparation and that additional N fertilisation would only be required from the fourth year onwards. On sandier soils, N fertilisation would probably have to commence sooner. It may be prudent to re-investigate the practice of providing nutrients, especially nitrogen (N). Ill-considered addition of N could lead to over-supply (especially on heavier soils) and a waste, since N uptake, shoot growth and yields seem to reach plateaus in response to increasing N in the soil (Spayd et al., 1993; Keller & Koblet, 1995). The unutilised NO₃ in the soil could be leached out of the soil profile and may also result in the eutrophication of nearby water sources and rivers (Good & Beatty, 2011).

According to Myburgh et al., (1996) the water requirement of grapevines (on the same site) during their first two years of growth is 55.4 % and 34.5 %, respectively, lower than the amount of irrigation generally required by an established vineyard in full production. It is important that fertilisation programmes and irrigation scheduling be done in accordance with the soil conditions and the specific requirements of the vineyard as determined by its age, vigour and yield potential. In the Western Cape with predominantly acid soils (Conradie, 1988), an abundance of N in the presence of adequate soil water may increase the production of N₂O, thereby further contributing to GHG emissions (Good & Beatty, 2011; Saayman, 2016).

Vineyard relocation

It is commonly predicted that (more) vineyards will be established at higher latitudes and higher elevations in future where projected climates will be more conducive to high quality production (Jones et al., 2005; Duchêne et al., 2010; Keller, 2010; Hannah et al., 2013; Fraga et al., 2016, 2017; Cabré & Nunez, 2020). The current European regulations may however prevent expansion to other regions, since there are strict specifications for Wines of Origin regarding the production area, vineyards, cultivars, and winemaking practices (EFOW, 2019). Moving vineyards to higher elevations also have disadvantages, such as the difficulty of access and the risk of erosion and damage by field fires (Wooldridge, 2007). Also in South Africa, wine grape producing areas are gradually expanding eastwards to the Cape South Coast region, where the current climate is comparable with the climate experienced in the Coastal Region a few decades ago (Southey, 2017). According to Hannah et al., (2013), vineyards are known to have long-lasting effects on the environment and their relocation may lead to conversion of natural vegetation, with substantial implications for conservation of ecosystems. Furthermore, existing viticultural areas may not necessarily be abandoned in the process and the vines may be replaced by other crops or the areas utilised for urban development.

There is a growing preference by consumers for environmentally friendly produce (Hannah et al., 2013; Medrano et al., 2015b), which might serve as an incentive for the wine industry to investigate, quantify and reduce its GHG emissions (and therefore its impact on climate change) and improve the management and conservation of natural resources (Schultz, 2016). The carbon and water footprints are also becoming increasingly important in food and wine trades and concerns about the water footprint (WFP) of grape and wine production are raised (Medrano et al., 2015a).

Any decision made or action performed should be based on real data and scientific knowledge with a good understanding of its multi-faceted effects on the agro-system (Fig. 6). The ultimate goal is the attainment of "harmony between grape and wine production, the environment and social aspects, while still maintaining economic viability" (Hunter et al., 2011).

Distinctive product character

Within any specific region, grape ripening dynamics are expected to change (even with adapted cultivation practices) with an increase in ambient temperature, resulting in a shorter overall harvesting period (Anderson et al., 2008; Clingeleffer et al., 2013). Due to earlier and faster grape ripening, unbalanced juice composition (previously mentioned) may affect the typical flavour profile and mouth-feel normally associated with that region. This is more relevant to warmer regions, since in cool climates a faster and more complete ripening process may even result in improved wine quality (Jones et al., 2005). Within limits, the wine quality and style may be controlled by changing the harvest date to meet certain ripeness criteria (Hunter et al., 2004; Nadal & Hunter, 2007; Hunter & Bonnardot, 2011; Hunter et al.,, 2014; Hunter & Volschenk, 2017; Terblanche, 2019).

The altered grape and juice composition and balance may also require adaptation of practices in wineries. A higher grape sugar content may lead to sluggish or stuck fermentations (with associated risks of the development of off-flavours) that might require the development of new wine yeasts that are better adapted to the new conditions (Anderson et al., 2008). However, the potential higher alcohol levels of such wines may cause practices such as the dilution of grape juice and/or the removal of alcohol from wines to become more widely used (Mira de Orduna, 2010). The increased importance of temperature control in the cellar would increase the cost of infrastructure (Anderson et al., 2008). It is thus expected that higher investment as well as more interventions in the cellar will be required to support desired aroma and wine styles, but within the boundaries of local winemaking regulations (Mira de Orduna, 2010).

A gradual change in wine styles across estates (within production regions) seems unavoidable (Wooldridge, 2007; Jones, 2010; Koch & Oehl, 2018), but it would not be a major problem should the market accept changes in the typicity of wines (Duchene et al., 2010) and the taste of the consumer evolves with the changes in wine style (Tate, 2001).

Current winemaking regions are associated with their distinctive wine style or cultivar, be it as a result of official legislation (Anderson et al., 2008; Webb et al., 2013) or more informal means, such as experience, local culture and tradition (Trombi et al., 2011), or the production of consistently outstanding quality (Davis et al., 2019). Wine regions are often major socio-economic role players that contribute significantly to national exports and tourism (Fraga et al., 2017). The rural tourism sector depends to a large extent on the surrounding vineyards and the abandonment of traditional cultivars and/or changes in the crops cultivated may have serious repercussions for local tourism, the economy and culture. It is imperative that these concerns are considered at various levels, since socio-economic issues, politics and regulations also have significant impact on the wine industry (Mozell & Thach, 2014).

 

CONCLUSIONS

The challenges faced by the wine industry in South Africa are similar to those in the rest of the world. It is foreseen that producers will have to cultivate their grapevines in higher atmospheric CO₂ levels and in warmer, mostly drier conditions. Climatic variability is also projected to increase, which would necessitate an improvement in the resilience of grapevines against adverse and fluctuating growth conditions. The need for producers to access and apply available climatic, environmental and technical information to ensure sustainable production is expected to increase. Dedicated research and knowledge transfer would make it possible to put timeous strategies in place to increase the adaptive capacity of the industry. Most of the adaptation practices that are recommended in this paper to address the different climatic conditions in future are based on research already done in various regions of the world. Improved collaboration and knowledge transfer between wine producing countries at international level may show that the climatic future of a particular region is already a reality in another.

 

LITERATURE CITED

Anderson, K., Findlay, C., Fuentes, S. & Tyerman, S., 2008. Viticulture, wine and climate change. Garnaut Climate Change Review, June 2008. pp. 1-22.         [ Links ]

Archer, E. & Hunter, J.J., 2005. Vine roots play an important role in determining wine quality. WineLand, Winetech Technical. March. https://www.wineland.co.za/vine-roots-play-an-important-role-in-determining-wine-quality/        [ Links ]

Archer, E. & Hunter, J.J., 2010. Practices for sustainable viticulture. Part 3. Planting of vines. WineLand, Winetech Technical Yearbook 2010. https://www.researchgate.net/publication/267623640_Practices_for_sustainable_viticulturePartIIIPlantingofvines.         [ Links ]

Archer, E., Swanepoel, J.J. & Strauss, H.C., 1988. Effect of plant spacing and trellising systems on grapevine root distribution. In: The grapevine root and its environment. Department of Agriculture and Water Supply, Technical Communication 215. Government Printer: Pretoria, South Africa. pp. 74-87.         [ Links ]

Barbagallo, M.G., Guidoni, S. & Hunter, J.J., 2011. Variation in berry size and qualitative characteristics of Vitis vinifera L. cv. Syrah. S. Afr. J. Enol. Vitic. 32, 129-136. https://doi.org/10.21548/32-1-1372        [ Links ]

Benhin, J.K.A., 2006. Climate change and South African agriculture: impacts and adaptation options. CEEPA Discussion Paper No. 21. Centre for Environmental Economics and Policy in Africa, University of Pretoria. https://www.weadapt.org/sites/weadapt.org/files/legacy-new/knowledge-base/files/5370f181a5657504721bd5c21csouth-african-agriculture.pdf .         [ Links ]

Blanco-Canqui, H. Shaver, T.M., Lindquist, J.L., Shapiro, C.A., Elmore, R.W., Francis, C.A. & Hergert, G.W., 2015. Cover crops and ecosystem services: insights from studies in temperate soils. Agron. J. 107(6), 24492474. https://doi.org/10.2134/agronj15.0086        [ Links ]

Bois, B., 2019. Assessment of climate change impacts on water availability for vitiviniculture worldwide using different potential evapotranspiration methods. Proc. 21^th Int. GiESCO Symp., June 2019, Thessaloniki, Greece. p. 26.         [ Links ]

Bonfante, A., Basile, A., De Lorenzi, F., Langella, G., Terribile, F. & Menenti, M., 2010. The adaptative capacity of a viticultural area (Valle Telesina, Southern Italy) to climate changes. Proc. 8^th Int. Terroir Congr., June 2010, Soave, Italy. pp. 3-96 - 3-101.         [ Links ]

Bonnardot, V.A., Planchon, O., Carey, V. & Cautenet, S., 2002. Diurnal wind, relative humidity and temperature variation in the Stellenbosch-Groot Drakenstein wine-growing area. S. Afr. J. Enol. Vitic. 23(2), 62-71. https://doi.org/10.21548/23-2-2156        [ Links ]

Bota, J., Tomás, M., Flexas, J., Medrano, H. & Escalona, J.M., 2016. Differences among grapevine cultivars in their stomatal behavior and water use efficiency under progressive water stress. Agric. Water Manage. 164, 91-99. https://doi.org/10.1016/j.agwat.2015.07.016        [ Links ]

Cabré, F. & Nuñez, M., 2020. Impacts of climate change on viticulture in Argentina. Reg. Environ. Change 20, 12. https://doi.org/10.1007/s10113-020-01607-8        [ Links ]

Caffarra, A. & Eccel, E., 2011. Projecting the impacts of climate change on the phenology of grapevine in a mountain area. Aust. J. Grape Wine Research. 17(1), 52-61. https://doi.org/10.1111/j.1755-0238.2010.00118.x        [ Links ]

Carey, V.A., 2001. Spatial characterisation of natural terroir units for viticulture in the Bottelaryberg-Simonsberg-Helderberg winegrowing area. MScAgric thesis, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa. https://scholar.sun.ac.za/handle/10019.1/52459        [ Links ]

Council for Agricultural Science and Technology [CAST], 2004. Climate change and greenhouse gas mitigation: challenges and opportunities for agriculture. Task Force Report no. 141. https://www.cast-science.org/publication/climate-change-and-greenhouse-gas-mitigation-challenges-and-opportunities-for-agriculture/        [ Links ]

Clingeleffer, PR., 2010. Plant management research: status and what it can offer to address challenges and limitations. Aust. J. Grape Wine Research. 16, 25-32. https://doi.org/10.1111/j.1755-0238.2009.00075.x        [ Links ]

Clingeleffer, P.R., Davis, H.P. & Tarr, C.R., 2013. Measurement of phenology, growth characteristics and berry composition to identify winegrape varieties adapted to future climate scenarios. Proc. 18^th Int. GiESCO Symp., July 2013, Porto, Portugal. pp. 987-991.         [ Links ]

Confronting Climate Change [CCC]., n.d. Confronting Climate Change. A South African fruit & wine initiative. https://www.climatefruitandwine.co.za/Default.aspx        [ Links ]

Confronting Climate Change [CCC]., 2009. South African Fruit and Wine Climate Change Program, Component 1: a review. February. http://www.ipw.co.za/content/pdfs/climate/eng/Climate_Change_7bl_final.pdf        [ Links ]

Confronting Climate Change [CCC]., 2019. Benchmark report 2019. South African wine grapes.         [ Links ]

Conradie, W.J., 1988. Effect of soil acidity on grapevine root growth and the role of roots as a source of nutrient reserves. In: The grapevine root and its environment. Department of Agriculture and Water Supply, Technical Communication 215. Government Printer: Pretoria, South Africa. pp. 16-29.         [ Links ]

Conradie, W.J., Van Zyl, J.L. & Myburgh, P.A., 1996. Effect of soil preparation depth on nutrient leaching and nutrient uptake by young Vitis vinifera L. cv. Pinot noir. S. Afr. J. Enol. Vitic. 17, 43-52. https://doi.org/10.21548/17-2-2257        [ Links ]

Creasy, G.L. & Creasy, L.L., 2009. Grapes. In: Atherton, J. & Rees, A. (eds). Crop Production Science in Horticulture, 16. CABI: Oxfordshire, UK.         [ Links ]

Davis, R.E., Dimon, R.A., Jones, G.V. & Bois, B., 2019. The effect of climate on Burgundy vintage quality rankings. OENO One 53(1), 59-73. https://doi.org/10.20870/oeno-one.2019.53.L2359        [ Links ]

De Kock Communications [DKC]., 2015. SA Wine Industry raises its GDP contribution, generates more jobs. Press release. 3 Feb 2015. http://www.sawis.co.za/info/download/Press_release_2015.pdf        [ Links ]

Dokoozlian, N.K., 1999. Chilling temperature and duration interact on the budbreak of 'Perlette' grapevine cuttings. Hortic. Sci. 34, October. https://doi.org/10.21273/HORTSCI.34.6.1        [ Links ]

Duchêne, E., Huard, F., Dumas, V., Schneider, C. & Merdinoglu, D., 2010. The challenge of adapting grapevine varieties to climate change. Clim. Res. 41, 193-204. https://doi.org/10.3354/cr00850        [ Links ]

Edwards, E.J., Unwin, D., Kilmister, R. & Treeby, M., 2017. Multi-seasonal effects of warming and elevated CO₂ on the physiology, growth and production of mature, field grown, Shiraz grapevines. OENO One 51(2), 127-132. https://doi.org/10.20870/oeno-one.2017.5L2.1586        [ Links ]

European Federation of Origin Wines [EFOW]., 2019. EU rules applicable to origin wines. http://efow.eu/eu-rules-applicable-to-origin-wines/        [ Links ]

Fraga, H., García de Cortázar Atauri, I., Malheiro, A.C., Moutinho-Pereira, J. & Santos, J.A., 2017. Viticulture in Portugal: a review of recent trends and climate change projections. OENO One 51(2), 61-69. https://doi.org/10.20870/oeno-one.2017.51.2.1621        [ Links ]

Fraga, H., García de Cortázar Atauri, I., Malheiro, A.C. & Santos, J.A., 2016. Modelling climate change impacts on viticultural yield, phenology and stress conditions in Europe. Glob. Change Biol. 22, 3774-3788. https://doi.org/10.1111/gcb.13382        [ Links ]

FTI Consulting [FTI]., 2021. Macro-economic impact of the wine industry on the South African economy. http://www.sawis.co.za/info/download/Macro-economic_Impact_of_the_Wine_Industry_2019_Final_(2).pdf        [ Links ]

Good, A.G. & Beatty, P.H., 2011. Fertilizing nature: a tragedy of excess in the commons. PLOS Biology 9, e1001124. https://doi.org/10.1371/journal.pbio.1001124        [ Links ]

Gray, J.D. & Coombe, B.G., 2009. Variation in Shiraz berry size originates before fruitset but harvest is a point of resynchronisation for berry development after flowering. Aust. J. Grape Wine Research. 15, 156-165. https://doi.org/10.1111/j.1755-0238.2009.00047.x        [ Links ]

Hall, A. & Jones, G.V., 2009. Effect of potential atmospheric warming on temperature-based indices describing Australian winegrape growing conditions. Aust. J. Grape Wine Research. 15, 97-119. https://doi.org/10.1111/j.1755-0238.2008.00035.x        [ Links ]

Hannah, L., Roehrdanz, P.R., Ikegami, M., Shepard, A. V., Shaw, M.R., Tabor, G., Zhi, L., Marquet, P.A. & Hijmans, R.J., 2013. Climate change, wine and conservation. PNAS 110, 6907-6912. https://doi.org/10.1073/pnas.1210127110        [ Links ]

Hunter, J.J., 1998a. Plant spacing implications for grafted grapevine I. Soil characteristics, root growth, dry matter partitioning, dry matter composition and soil utilisation. S. Afr. J. Enol. Vitic. 19, 25-34. https://doi.org/10.21548/19-2-2242        [ Links ]

Hunter, J.J., 1998b. Plant spacing implications for grafted grapevine II. Soil water, plant water relations, canopy physiology, vegetative and reproductive characteristics, grape composition, wine quality and labour requirements. S. Afr. J. Enol. Vitic. 19, 35-51. https://doi.org/10.21548/19-2-22423        [ Links ]

Hunter, J.J., 2000. Implications of seasonal canopy management and growth compensation in grapevine. S. Afr. J. Enol. Vitic. 21, 81-91. https://doi.org/10.21548/21-2-2215        [ Links ]

Hunter, J.J., Archer, E., Strever, A. & Volschenk, C.G., 2011. Integrative strategies for sustainable viticulture and terroir valorisation. Proc. 17^th Int. GiESCO Symp., Aug-Sep 2011, Asti-Alba, Italy. pp. 73-78.         [ Links ]

Hunter, J.J. & Bonnardot, V., 2011. Suitability of some climatic parameters for grapevine cultivation in South Africa, with focus on key physiological processes. S. Afr. J. Enol. Vitic. 32, 137-154. https://doi.org/10.21548/32-1-1374        [ Links ]

Hunter, J.J. & Myburgh, P.A., 2001. Ecophysiological basis for water management of vineyards in South Africa, with particular reference to environmental limitations. Proc. 12^th meeting of the study group for vine training systems, July 2001, Montpellier, France. pp. 23-43.         [ Links ]

Hunter, J.J., Pisciotta, A., Volschenk, C.G., Archer, E., Novello, V., Kraeva, E., Deloire, A. & Nadal, M., 2004. Role of harvesting time/optimal ripeness in zone/terroir expression. Proc. Joint Conf. (GiESCO, OIV, SASEV) Viticultural Zoning, November 2004, Cape Town, South Africa. pp. 466478.         [ Links ]

Hunter, J.J. & Volschenk, C.G., 2001. Effect of altered canopy:root volume ratio on grapevine growth compensation. S. Afr. J. Enol. Vitic. 22, 27-30. https://doi.org/10.21548/22-1-2163        [ Links ]

Hunter, J.J. & Volschenk, C.G., 2017. Chemical composition and sensory properties of non-wooded and wooded Shiraz (Vitis vinifera L.) wine as affected by vineyard row orientation and grape ripeness level. J. Sci. Food and Agric. https://doi.org/10.1002/jsfa.8763        [ Links ]

Hunter, J.J., Volschenk, C.G. & Bonnardot, V., 2010. Linking grapevine row orientation to a changing climate in South Africa. Proc. Int. Intervitis-Interfructa Congr., March 2010, Stuttgart, Germany.         [ Links ]

Hunter, J.J., Volschenk, C.G. & Booyse, M., 2017. Vineyard row orientation and grape ripeness level effects on vegetative and reproductive growth characteristics of Vitis vinifera L. cv. Shiraz/101-14 Mgt. Eur. J. Agron. 84, 47-57. https://doi.org/10.1016/j.eja.2016.12.004        [ Links ]

Hunter, J.J., Volschenk, C.G., Marais, J. & Fouché, G.W., 2004. Composition of Sauvignon blanc grapes as affected by pre-véraison canopy manipulation and ripeness level. S. Afr. J. Enol. Vitic. 25, 13-18. https://doi.org/10.21548/25-1-2132        [ Links ]

Hunter, J.J., Volschenk, C.G., Novello, V., Pisciotta, A., Booyse, M. & Fouché, G.W., 2014. Integrative effects of vine water relations and grape ripeness level of Vitis vinifera L. cv. Shiraz/Richter 99. II. Grape composition and wine quality. S. Afr. J. Enol. Vitic. 35, 359-374. https://doi.org/10.21548/35-2-1022        [ Links ]

Hunter, J.J., Volschenk, C.G. & Zorer, R., 2016. Vineyard row orientation of Vitis vinifera L. cv. Shiraz/101-14 Mgt: climatic profiles and vine physiological status. Agric. Forest Meteorol. 228, 104-119. https://doi.org/10.1016/j.agrformet.2016.06.013        [ Links ]

Integrated Carbon Observation System [ICOS]., n.d. Standardised greenhouse gas measurements throughout Europe. https://www.icos-cp.eu/        [ Links ]

IPCC., 2014. Climate change 2014. Synthesis report. Summary for policymakers. https://www.ipcc.ch/site/assets/uploads/2018/05/SYR_AR5_FINAL_full_wcover.pdf        [ Links ]

IPCC., 2019. Climate change and land. Special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. Summary for policymakers (approved draft). https://www.ipcc.ch/site/assets/uploads/2019/08/Edited-SPM_Approved_Microsite_FINAL.pdf        [ Links ]

Jackson, R.S., 2014 (4^th ed). Wine science: principles and applications. Academic Press, Elsevier. pp. 185-190.         [ Links ]

Jones, G.V., 2007. Climate change: observations, projections and general implications for viticulture and wine production. Proc. 12^th Brazilian Congr. Vitic. Enol., Brazil. pp. 55-66.         [ Links ]

Jones, G.V., 2010. Climate, grapes, and wine: structure and suitability in a variable and changing climate. Proc. 8^th Int. Terroir Congr., June 2010, Soave, Italy. pp. 3-3 - 3-8.         [ Links ]

Jones, G.V. & Davis, R.E., 2000. Climate influences on grapevine phenology, grape composition, and wine production and quality for Bordeaux, France. Am. J. Enol. Vitic. 51, 249-261.         [ Links ]

Jones, G.V. & Webb, L.B., 2010. Climate change, viticulture, and wine: challenges and opportunities. J. Wine Res. 21, 103-106. https://doi.org/10.1080/09571264.2010.530091        [ Links ]

Jones, G.V., White, M.A., Cooper, O.R. & Storchmann, K., 2005. Climate change and global wine quality. Climatic Change 73, 319-343. https://doi.org/10.1007/s10584-005-4704-2        [ Links ]

Keller, M., 2005. Deficit irrigation and vine mineral nutrition. Am. J. Enol. Vitic. 56, 267-283.         [ Links ]

Keller, M., 2010. Managing grapevines to optimise fruit development in a challenging environment: a climate change primer for viticulturists. Aust. J. Grape Wine Research 16, 56-69. https://doi.org/10.1111/j.1755-0238.2009.00077.x        [ Links ]

Keller, M. & Koblet, W., 1995. Dry matter and leaf area partitioning, bud fertility and second season growth of Vitis vinifera L.: responses to nitrogen supply and limiting irradiance. Vitis 34, 77-83.         [ Links ]

Koch, B. & Oehl, F., 2018. Climate change favors grapevine production in temperate zones. Agricultural Sciences 9, 247-263. https://doi.org/10.4236/as.2018.93019        [ Links ]

Lal, R., 2018. Digging deeper: a holistic perspective of factors affecting soil organic carbon sequestration in agroecosystems. Glob. Change Biol. 24, 3285-3301. https://doi.org/10.1111/gcb.14054        [ Links ]

Leibar, U., Aizpurua, A., Unamunzaga, O., Pascual, I. & Morales, F., 2015. How will climate change influence grapevine cv. Tempranillo photosynthesis under different soil textures? Photosynth. Res. 124, 199-215. https://doi.org/10.1007/s11120-015-0120-2        [ Links ]

Martínez-Lüscher, J., Morales, F., Sánchez-Díaz, M., Delrot, S., Aguirreolea, J., Gomes, E. & Pascual, I., 2015. Climate change conditions (elevated CO₂ and temperature) and UV-B radiation affect grapevine (Vitis vinifera cv. Tempranillo) leaf carbon assimilation, altering fruit ripening rates. Plant Sci. 236, 168-176. https://doi.org/10.1016/j.plantsci.2015.04.001        [ Links ]

Medrano, H., Tomás, M., Martorell, S., Escalona, J.M., Pou, A., Fuentes, S., Flexas, J. & Bota, J., 2015a. Improving water use efficiency of vineyards in semi-arid regions. A review. Agron. Sustain. Dev. 35, 499-517. https://doi.org/10.1007/s13593-014-0280-z        [ Links ]

Medrano, H., Tomás, M., Martorell, S., Flexas, J., Hernández, E., Rosselló, J., Pou, A., Escalona, J.M., Bota, J., 2015b. From leaf to whole-plant water use efficiency (WUE) in complex canopies: limitations of leaf WUE as a selection target. Crop J. 3, 220-228. https://doi.org/10.1016/j.cj.2015.04.002        [ Links ]

Midgley, G.F., Chapman, R.A., Hewitson, B., Johnston, P., De Wit, M., Ziervogel, G., Mukheibir, P., Van Niekerk, L., Tadross, M., Van Wilgen, B.W., Kgope, B., Morant, P.D., Theron, A., Scholes, R.J. & Forsyth, G.G., 2005. A status quo, vulnerability and adaptation assessment of the physical and socio-economic effects of climate change in the Western Cape. Report to the Western Cape Government, Cape Town, South Africa. CSIR Report No. ENV-S-C 2005-073, Stellenbosch. https://open.uct.ac.za/handle/11427/17144        [ Links ]

Midgley, S., New, M., Methner, N., Cole, M., Cullis, J., Drimie, S., Dzama, K., Guillot, B., Harper, J., Jack, C., Johnston, P., Knowles, T., Louw, D., Mapiye, C., Oosthuizen, H., Smit, J. & Van den Broek, D., 2016. A status quo review of climate change and the agriculture sector of the Western Cape province. https://www.greenagri.org.za/assets/documents-/SmartAgri/Briefs-/Smart-Agri-Status-Quo-Review-2016.pdf        [ Links ]

Mira de Orduña, R., 2010. Climate change associated effects on grape and wine quality and production. Food Res. Int. 43, 1844-1855. https://doi.org/10.1016/j.foodres.2010.05.001        [ Links ]

Montmasson-Clair, G. & Zwane, M., 2016. Climate change adaptation and agriculture in South Africa: a policy assessment. Report compiled for WWF-SA, South Africa. http://awsassets.wwf.org.za/downloads/wwf_pfu_policybrief_lowres_pdf        [ Links ]

Morales-Castilla, I., De Cortázar-Atauri, I.G., Cook, B.I., Lacombe, T., Parker, A., Van Leeuwen, C., Nicholas, K.A. & Wolkovich, E.M., 2020. Diversity buffers winegrowing regions from climate change losses. PNAS 117(6), 2864-2869. https://doi.org/10.1073/pnas.1906731117        [ Links ]

Moran, M., Petrie, P. & Sadras, V., 2019. Effects of late pruning and elevated temperature on phenology, yield components, and berry traits in Shiraz. Am. J. Enol. Vitic. 70, 9-18. https://doi.org/10.5344/ajev.2018.18031        [ Links ]

Mozell, M.R. & Thach, L., 2014. The impact of climate change on the global wine industry: challenges & solutions. Wine Econ. Policy 3, 81-89. https://doi.org/10.1016/j.wep.2014.08.001        [ Links ]

Myburgh, P.A. & Howell, C.L., 2014. The impact of wastewater irrigation by wineries on soils, crop growth and product quality. WRC Report No K5/1881/14. http://www.sawislibrary.co.za/dbtextimages/MyburghPA9.pdf        [ Links ]

Myburgh, P.A., Van Zyl, J.L. & Conradie, W.J., 1996. Effect of soil depth on growth and water consumption of young Vitis vinifera L. cv. Pinot noir. S. Afr. J. Enol. Vitic. 17, 53-62. https://doi.org/10.21548/17-2-2258        [ Links ]

Nadal, M. & Hunter, J.J., 2007. Different wine styles as related to ripeness level of Syrah/R 99 grapes. Proc. Int. Intervitis-Interfructa Congr., March 2010, Stuttgart, Germany. pp. 139-148.         [ Links ]

Neethling, E., Barbeau, C., Quénol, H. & Barbeau, G., 2013. Study on the sensitivity and adaptability of viticultural practices: wine growers' responses to climate variability. Proc. 18^th Int. GiESCO Symp., July 2013, Porto, Portugal. pp. 283-287.         [ Links ]

NOAA-ESRL, 2021. Trends in atmospheric carbon dioxide. https://www.esrl.noaa.gov/gmd/ccgg/trends/global.html        [ Links ]

Organisation Internationale De La Vigne Et Du Vin [OIV], 2013. International list of vine varieties and their synonyms. http://www.oiv.int/public/medias/2273/oiv-liste-publication-2013-complete.pdf        [ Links ]

Peccoux, A., Loveys, B., Zhu, J., Gambetta, G.A., Delrot, S., Vivin, P., Schultz, H.R., Ollat, N. & Dai, Z., 2018. Dissecting the rootstock control of scion transpiration using model-assisted analyses in grapevine. Tree Physiol. 38(7), 1026-1040. https://doi.org/10.1093/treephys/tpx153        [ Links ]

Pérez, F.J. & Rubio, S., 2021. Relationship between bud cold hardiness and budbreak in two Vitis vinifera L cultivars, Chardonnay and Thompson Seedless. J. Plant Growth Regul. https://doi.org/10.1007/s00344-021-10343-0        [ Links ]

Quénol, H., De Cortazar Atauri, I.G., Bois, B., Sturman, A., Bonnardot, V. & Le Roux, R., 2017. Which climatic modeling to assess climate change impacts on vineyards? OENO One 51, 91-97. https://doi.org/10.20870/oeno-one.2017.51.2.1869        [ Links ]

Republic of South Africa [RSA], Department of Water and Sanitation., 2019. List of registered dams, April 2019. Dam Safety Office. http://www.dwa.gov.za/DSO/publications.aspx        [ Links ]

Saayman, D. 2016. Maintenance fertilisation of macro- and micro-elements. In: Conradie, K. (ed.) Fertiliser guidelines for the wine industry. Villa Academy: Kempton Park, South Africa. pp. 35-74.         [ Links ]

Salazar-Parra, C., Aguirreolea, J., Sánchez-Díaz, M., Irigoyen, J.J. & Morales, F., 2012. Photosynthetic response of Tempranillo grapevine to climate change scenarios. Ann. Appl. Biol. 161, 277-292. https://doi.org/10.1111/j.1744-7348.2012.00572.x        [ Links ]

Santos, J.A., Fraga, H., Malheiro, A.C., Moutinho-Pereira, J., Dinis, L.-T., Correia, C., Moriondo, M., Leolini, L., Dibari, C., Costafreda-Aumedes, S., Kartschall, T., Menz, C., Molitor, D., Junk, J., Beyer, M. & Schultz, H.R., 2020. A review of the potential climate change impacts and adaptation options for European viticulture. Appl. Sci. 10, 3092. https://doi.org/10.3390/app10093092        [ Links ]

Schultz, H.R., 2000. Climate change and viticulture: a European perspective on climatology, carbon dioxide and UV-B effects. Aust. J. Grape Wine Research 6, 2-12. https://doi.org/10.1111/j.1755-0238.2000.tb00156.x        [ Links ]

Schultz, H.R., 2011. Climatology, ecophysiology, vine performance - a set of strange connections. Proc. 17^th Int. GiESCO Symp., Aug-Sep 2011, Asti-Alba, Italy. pp. 227-229.         [ Links ]

Schultz, H.R., 2016. Global climate change, sustainability, and some challenges for grape and wine production. J. Wine Econ. 11, 181-200. https://doi.org/10.1017/jwe.2015.31        [ Links ]

Schultz, H.R. & Stoll, M., 2010. Some critical issues in environmental physiology of grapevines: future challenges and current limitations. Aust. J. Grape Wine Research. 16, 4-24. https://doi.org/10.1111/j.1755-0238.2009.00074.x        [ Links ]

Schulze, R.E., 2016. Adaptation to climate change in South Africa's agricultural sector. In: Schulze, R.E. (ed.) Handbook for farmers, officials and other stakeholders on adaptation to climate change in the agriculture sector within South Africa. Section A: Agriculture and climate change in South Africa: setting the scene, Chapter A.         [ Links ]

Schwab, A. & Maass, U., 2010. Climate change - variety change? Proc. 8^th Int. Terroir Congr., June 2010, Soave, Italy. pp. 3-62 - 3-64.         [ Links ]

Seguin, B. & Garcia de Cortazar, I., 2015. Climate warming: consequences for viticulture and the notion of 'terroirs' in Europe. Acta Hortic. 689, 6170. https://doi.org/10.17660/ActaHortic.2005.689.3        [ Links ]

Serra, I., Strever, A., Myburgh, P.A. & Deloire, A., 2014. Review: the interaction between rootstocks and cultivars (Vitis vinifera L.) to enhance drought tolerance in grapevine. Aust. J. Grape Wine Research. 20, 1-14. https://doi.org/10.1111/ajgw.12054        [ Links ]

Simonneau, T., Lebon, E., Coupel-Ledru, A., Marguerit, E., Rossdeutsch, L. & Ollat, N., 2017. Adapting plant material to face water stress in vineyards: which physiological targets for an optimal control of plant water status? OENO One 51, 167-179. https://doi.org/10.20870/oeno-one.2017.51.2.1870        [ Links ]

South African Wine Industry Information & Systems [SAWIS], 2015. Macroeconomic impact of the wine industry on the South African economy (also with reference to the impacts on the Western Cape), Final report. Executive summary. http://www.sawis.co.za/info/download/Macro-economic_impact_study_-_Final_Report_Version_4_30Jan2015-corrected.pdf .         [ Links ]

South African Wine Industry Information & Systems [SAWIS], 2018. SA Wine Industry Statistics 2018 nr.43. http://www.sawis.co.za/info/download/Book_2018_statistics_year_english_final.pdf.         [ Links ]

South African Wine Industry Information & Systems [SAWIS], 2020. SA Wine Industry Statistics 2020 nr.45. http://www.sawis.co.za/info/download/Book_2020_statistics_Final_1.pdf        [ Links ]

Southey, J.M., 1992. Grapevine rootstock performance under diverse conditions in South Africa. In: Wolpert, J.A., Walker, M.A. & Weber, E. (eds). Proc. Rootstock Seminar: A worldwide Perspective, June 1992, Reno, Nevada, USA. pp. 27-51.         [ Links ]

Southey, T.O., 2017. Integrating climate and satellite remote sensing to assess the reaction of Vitis vinifera L. cv. Cabernet Sauvignon to a changing environment. PhD thesis, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa. https://scholar.sun.ac.za/handle/10019.1/101124        [ Links ]

Southey, T.O., 2021. TerraClim - high resolution temperature layers are available and so much more. WineLand, Winetech Technical. April. https://wineland.b-cdn.net/wp-content/uploads/2021/05/High-resolution-temperature-layers-are-available-and-so-much-more.pdf        [ Links ]

Spayd. S.E., Wample, R.L., Stevens, R.G., Evans, R.G. & Kawakami, A.K., 1993. Nitrogen fertilization of White Riesling in Washington: effects on petiole nutrient concentration, yield, yield components, and vegetative growth. Am. J. Enol. Vitic. 44, 378-386.         [ Links ]

Sturman, A., Zawar-Reza, P., Soltanzadeh, I., Katurji, M., Bonnardot, V., Parker, A.K., Trought, M.C.T., Quénol, H., Le Roux, R., Gendig, E. & Schulmann, T., 2017. The application of high-resolution atmospheric modelling to weather and climate variability in vineyard regions. OENO One 51(2), 99-105. https://doi.org/10.20870/oeno-one.2017.51.2.1538        [ Links ]

Sustainable Wine South Africa [SWSA]., n.d. Sustainable Wine South Africa (SWSA). Overview. https://www.wosa.co.za/swsa/en/Overview/        [ Links ]

Tate, A.B., 2001. Global warming's impact on wine. J. Wine Res. 12, 95109. https://doi.org/10.1080/09571260120095012        [ Links ]

Terblanche, E.L.A., 2019. The impact of grape ripeness level on berry and wine composition and potential wine style of Vitis vinifera L. cv. Pinotage. PhD thesis, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa. http://hdl.handle.net/10019.1/106248        [ Links ]

Tezza. L., Vendrame, N. & Pitacco, A., 2019. Disentangling the carbon budget of a vineyard: the role of soil management. Agric. Ecosyst. Environ. 272, 52-62. https://doi.org/10.1016/j.agee.2018.11.002        [ Links ]

Torregrosa, L., Bigard, A., Doligez, A., Lecourieux, D., Rienth, M., Luchaire, N., Pieri, P., Chatbanyong, R., Shahood, R., Farnos, M., Roux, C., Adiveze, A., Pillet, J., Sire, Y., Zumstein, E., Veyret, M., Le Cunff, L., Lecourieux, F., Saurin, N., Muller, B., Ojeda, H., Houel, C., Péros, J.-P., This, P., Pellegrino, A. & Romieu, C., 2017. Developmental, molecular and genetic studies on grapevine response to temperature open breeding strategies for adaptation to warming. OENO One 51(2), 155-165. https://doi.org/10.20870/oeno-one.2017.51.2.1587        [ Links ]

Trombi, G., Moriondo, M., Bindi, M., Fagarazzi, C., Ferrise, R. & Cai, M., 2011. The impacts of the climate change on Tuscan viticulture: qualities, areas and landscapes. Proc. 1^st Eur. Conf. Wine Food Tourism, April 2011, Volterra (Pisa), Italy. pp. 83-85.         [ Links ]

Tubiello, F.N., Salvatore, M., Condor Golec, R.D., Ferrara, A., Rossi, S., Biancalani, R., Federici, S., Jacobs, H. & Flammini, A., 2014. Agriculture, forestry and other land use emissions by sources and removals by sinks: 1990-2011 analysis. FAO Statistics Division Working Paper Series, ESS/14-02. http://www.fao.org/3/i3671e/i3671e.pdf        [ Links ]

United Nations Framework Convention on Climate Change [UNFCCC], 2011. Fact sheet: Climate change science - the status of climate change science today. https://unfccc.int/files/press/backgrounders/application/pdf/press_factsh_science.pdf        [ Links ]

Van Huyssteen, L., 1988. Soil preparation and grapevine root distribution - a qualitative and quantitative assessment. In: The grapevine root and its environment. Department of Agriculture and Water Supply, Technical Communication 215. Government Printer: Pretoria, South Africa. pp. 1-15.         [ Links ]

Van Leeuwen, C. & Destrac-Irvine, A., 2017. Modified grape composition under climate change conditions requires adaptations in the vineyard. OENO One 51(2), 147-154. https://doi.org/10.20870/oeno-one.2016.0.0.1647        [ Links ]

Van Leeuwen, C., Destrac-Irvine, A., Dubernet, M., Duchêne, E., Gowdy, M., Marguerit, E., Pieri, P., Parker, A., De Rességuier, L. & Ollat, N., 2019. An update on the impact of climate change in viticulture and potential adaptations. Agronomy 9(9), 514. https://doi.org/10.3390/agronomy9090514        [ Links ]

Van Leeuwen, C., Garnier, C., Agut, C., Baculat, B., Barbeau, G., Besnard, E., Bois, B., Boursiquot, J.-M., Chuine, I., Dessup, T., Dufourcq, T., Garcia-Cortazar, I., Marguerit, E., Monamy, C., Koundouras, S., Payan, J.-C., Parker, A., Renouf, V., Rodriguez-Lovelle, B., Roby, J.-P., Tonietto, J. & Trambouze, W., 2008. Heat requirements for grapevine varieties is essential information to adapt plant material in a changing climate. Proc. 7^th Int. Terroir Congr., May 2008, Nyon, Switzerland. pp. 222-227.         [ Links ]

Van Zyl, J.L. & Van Huyssteen, L., 1980. Comparative studies on wine grapes on different trellising systems: I. Consumptive water use. S. Afr. J. Enol. Vitic. 1(1), 7-14. https://doi.org/10.21548/1-1-2409        [ Links ]

Van Zyl, J.L. & Van Huyssteen, L., 1988. Irrigation systems - their role in water requirements and the performance of grapevines. S. Afr. J. Enol. Vitic. 9, 3-8. https://doi.org/10.21548/9-2-2299        [ Links ]

Visualviticulture. 2017. Western Cape topographic relief map http://visualviticulture.co.za/2017/04/23/western-cape-topographic-relief-map/        [ Links ]

Volschenk, C.G. & Hunter, J.J., 2001. Effect of seasonal canopy management on the performance of Chenin blanc/99 Richter grapevines. S. Afr. J. Enol. Vitic. 22, 36-40. https://doi.org/10.21548/22-1-2165        [ Links ]

Vondras, A.M., Gouthu, S., Schmidt, J.A., Petersen, A.-R. & Deluc, L.G., 2016. The contribution offlowering time and seed content to uneven ripening initiation among fruits within Vitis vinifera L. cv. Pinot noir clusters. Planta 243, 1191-1202. https://doi.org/10.1007/s00425-016-2474-x        [ Links ]

Weaver, R.J. & Mccune, S.B., 1960. Effects of overcropping on Alicante Bouschet grapevines in relation to carbohydrate nutrition and development of the vine. Proc. Am. Soc. Hort. Sci. 75, 341-353.         [ Links ]

Weaver, R.J. & Pool, R.M., 1968. Effect of various levels of cropping on Vitis vinifera grapevines. Am. J. Enol. Vitic. 19, 185-193.         [ Links ]

Webb, L.B., Watterson, I., Bhend, J., Whetton, P.H. & Barlow, E.W.R., 2013. Global climate analogues for winegrowing regions in future periods: projections of temperature and precipitation. Aust. J. Grape Wine Research. 19, 331-341. https://doi.org/10.1111/ajgw.12045        [ Links ]

Webb, L.B., Whetton, P.H. & Barlow, E.W.R., 2007. Modelled impact offuture climate change on the phenology of winegrapes in Australia. Aust. J. Grape Wine Research. 13, 165-175. https://doi.org/10.1111/j.1755-0238.2007.tb00247.x        [ Links ]

Western Cape Government [WCG], Department of Agriculture., 2016. Western Cape launches climate change action plan. http://www.elsenburg.com/news/western-cape-launches-climate-change-action-plan        [ Links ]

Western Cape Government [WCG], Department of Environmental Affairs and Development Planning., 2014. Western Cape climate change response strategy. https://www.westerncape.gov.za/text/2015/march/western_cape_climate_change_response_strategy_2014.pdf        [ Links ]

Western Cape Government [WCG], Departments of Environmental Affairs and Development Planning, and Agriculture., 2015. Climate change & the agricultural sector in the Western Cape: a review. Executive summary. https://www.greenagri.org.za/assets/documents-/SmartAgri/Executive-Summary-published-version.pdf        [ Links ]

Wines of South Africa [WOSA], 2021. Winegrowing areas. https://www.wosa.co.za/The-Industry/Winegrowing-Areas/Winelands-of-South-Africa/        [ Links ]

Wooldridge, J., 2007. A perspective on climate change II. Implications for global and South African viticulture. WineLand, Winetech Technical. October. https://www.wineland.co.za/a-perspective-on-climate-change-ii/        [ Links ]

Zeeman, A.S., 1981. Oplei. In: Burger, J. & Deist, J. (eds). Wingerdbou in Suid-Afrika, ARC Infruitec-Nietvoorbij, Stellenbosch, South Africa. pp. 185-201.         [ Links ]

Zinta, G., AbdElgawad, H., Peshev, D., Weedon, J.T., Van den Ende, W., Nijs, I. Janssens, I.A., Beemster, G.T.S. & Asard, H., 2018. Dynamics of metabolic responses to periods of combined heat and drought in Arabidopsis thaliana under ambient and elevated atmospheric CO₂. J. Exp. Bot. 69(8), 2159-2170. https://doi.org/10.1093/jxb/ery055.         [ Links ]

 

 

Submitted for publication: July 2021
Accepted for publication: October 2021

 

 

* Corresponding author: theronh@cput.ac.za
Acknowledgements: This research was conducted by H. Theron as part of her PhD studies undertaken at Stellenbosch University, South Africa.