Editing IPCC:AR6/WGII/Chapter-5 (section)

==== 5.4.3.3 Projected impacts on other crops ====

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Yield projections for crops other than cereals indicate mostly negative impacts on production due to a range of climate drivers ( ''high confidence'' ), with yield reductions similar to that of cereals expected in tropical, subtropical and semi-arid areas ( [[#Mbow--2019|Mbow et al., 2019]] ). [[#Springmann--2016|Springmann et al. (2016)]] , compared the projected global food availability for different food groups under the SSP2 2050 scenario and found reductions in availability were similar in cereals, fruit and vegetables, and root and tubers (with legumes and oilseed crops showing a smaller reduction).

Fruit and vegetables have not been subject to extensive or coordinated yield projections (Figure 5.8). Yield projections have been performed for individual crops and locations ( [[#Ruane--2014|Ruane, 2014]] ; [[#Adhikari--2015|Adhikari et al., 2015]] ; [[#Awoye--2017|Awoye et al., 2017]] ; [[#Ramachandran--2017|Ramachandran et al., 2017]] ), but more often crop suitability models have been used (SM5.3). Zhao (2019) introduced a modelling approach that could be used to generate yield projections for a wider range of annual crops. The discussion here also draws on reviews of more restricted experimental studies. Negative impacts of climate change on crop production are expected across many cropping systems (Figure 5.8). Apart from the direct effects of elevated carbon dioxide, most changes are expected to have negative effects on crop production. Changes in temperature and rainfall are most often mentioned as drivers of climate impacts, but expected changes in phenology, pests and diseases are also raising concerns. [[#Scheelbeek--2018|Scheelbeek et al. (2018)]] synthesised projections for vegetables and legumes, based on their response to climate factors under experimental conditions; in most cases, the magnitude of the changes is comparable to the RCP8.5 2100 forecasts. [[#Scheelbeek--2018|Scheelbeek et al. (2018)]] projected yield changes of: +22.0% (+11.6% to +32.5%) for a 250 ppm increase in CO 2 concentration; −34.7% (−44.6% to −24.9%) for a 50% reduction in water availability; −8.9% (−15.6% to −2.2%) for a 25% increase in ozone concentration; −31.5% for a 4°C increase in temperature (in papers with a baseline temperature of &gt;20°C). Overall, impacts are expected to be largely negative in regions where the temperature is currently above 20°C, while some yield gains are expected in cooler regions (provided that water availability and other conditions are maintained). [[#Scheelbeek--2018|Scheelbeek et al. (2018)]] did not consider changes in pest and disease pressure, which are projected to increase with warming (see SM5.3).

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'''Figure 5.8 |''' '''Synthesis of literature on the projected impacts of climate change on different cropping systems.''' The assessment includes projections of impacts on crop productivity over a range of emission scenarios and time periods. The projected impacts are disaggregated by the different climate and climate-related drivers. Impacts are reported as positive, negative or mixed. The assessment draws on &gt;60 articles published since AR5. The confidence is based on the evidence given in individual articles and on the number of articles. See '''SM5.2''' information for details.

Systematic assessments of climate response for root crops as a group are lacking ( [[#Raymundo--2014|Raymundo et al., 2014]] ; [[#Knox--2016|Knox et al., 2016]] ; [[#Manners--2018|Manners and van Etten, 2018]] ). Climate suitability is projected to increase for tropical root crops (SM5.3), and some studies have found that root crops will be less negatively impacted than cereals, but there is no consensus on this ( [[#Brassard--2008|Brassard and Singh, 2008]] ; [[#Adhikari--2015|Adhikari et al., 2015]] ; [[#Schafleitner--2016|Schafleitner, 2016]] ; [[#Manners--2021|Manners et al., 2021]] ). For potato, [[#Raymundo--2018|Raymundo et al. (2018)]] projected global yield reductions of 2–6% by 2055 under different RCPs, but with important differences among regions; tuber dry weight may experience reductions of 50–100% in marginal growing areas such as central Asia, while increases of up to 25% are expected in many high-yielding environments. Projections show yield increases of 6% per 100 ppm elevation in CO 2 but declines of 4.6% per degree Celsius and 2% per 10% decrease in rainfall ( [[#Fleisher--2017|Fleisher et al., 2017]] ). [[#Jennings--2020|Jennings et al. (2020)]] projected an overall increase in global potato production, but only if widespread adoption of adaptation measures is achieved. Although increases in CO 2 could produce positive yield responses, the effects of temperature may offset these potential benefits ( [[#Dua--2013|Dua et al., 2013]] ; [[#Raymundo--2014|Raymundo et al., 2014]] ). Warming offers the potential of longer growing seasons but can also have negative impacts through disrupted phenology and interactions with pests (Figure 5.8, [[#Bebber--2015|Bebber, 2015]] ; [[#Pulatov--2015|Pulatov et al., 2015]] ).

Global yield modelling is lacking for woody perennial crops. Experimental studies suggest negative impacts on yields due to reduced water supply and increased soil salinity, as well as from warming and ozone (although evidence was limited for these) ( [[#Alae-Carew--2020|Alae-Carew et al., 2020]] ). Increasing CO 2 is expected to increase yields, but only where other factors, such as warming, do not become yield-limiting ( [[#Alae-Carew--2020|Alae-Carew et al., 2020]] ). Many local projections include large uncertainty because of a lack of observational data and reliable parametrisation ( [[#Moriondo--2015|Moriondo et al., 2015]] ; [[#Mosedale--2016|Mosedale et al., 2016]] ; [[#Kerr--2018|Kerr et al., 2018]] ; [[#Mayer--2019b|Mayer et al., 2019b]] ). Most perennial crop models have found large negative impacts on yield and suitability, although CO 2 fertilisation and phenology are not always considered ( [[#Lobell--2011|Lobell and Field, 2011]] ; [[#Glenn--2013|Glenn et al., 2013]] ). Perennial crops are often grown in dryland areas where rainfall or irrigation water can be critical ( [[#Mrabet--2020|Mrabet et al., 2020]] ). Valverde (2015) found that yield losses in the Mediterranean region were largely driven by reduced rainfall, with maximum estimated yield losses of 5.4% for grape, 14.9% for olive and 27.2% for almond under a relatively hot and dry scenario (by 2041–2070). Moriondo (2015) highlight the need for perennial crop models to incorporate phenology and extreme climate events. Equally challenging is the need to estimate the impact of biotic changes, particularly climate-driven movement of pests and diseases ( [[#Ponti--2014|Ponti et al., 2014]] ; [[#Bosso--2016|Bosso et al., 2016]] ; [[#Schulze-Sylvester--2019|Schulze-Sylvester and Reineke, 2019]] ).

For cotton, experimental studies suggest positive impacts from rising CO 2 and temperature ( [[#Zhang--2017a|Zhang et al., 2017a]] ; [[#Jans--2021|Jans et al., 2021]] ), but projections show mixed impacts on yield, including large negative impacts in warmer regions due to heat, drought and the interaction of temperature with phenology ( [[#Yang--2014|Yang et al., 2014]] ; [[#Williams--2015|Williams et al., 2015]] ; [[#Adhikari--2016|Adhikari et al., 2016]] ; [[#Rahman--2018|Rahman et al., 2018]] ). Climate change is also expected to increase the demand for irrigation water, which will likely limit production ( [[#Jans--2021|Jans et al., 2021]] ). There are also concerns that fibre quality may deteriorate (e.g., air permeability of compressed cotton fibers) ( [[#Luo--2016|Luo et al., 2016]] ).

Higher temperatures and altered moisture levels are expected to present a food safety risk, particularly for above-ground harvested vegetables (Figures 5.8; 5.10). Warmer and wetter weather is anticipated to increase fungal and microbial growth on leaves and fruit, while altered flooding regimes increase the risk of crop contamination ( [[#Liu--2013|Liu et al., 2013]] ; [[#Uyttendaele--2015|Uyttendaele et al., 2015]] ). This is also true for perennial crops; for example, warming and climate variability can increase fungal contamination of grapes, including that associated with mycotoxins ( [[#Battilani--2016|Battilani, 2016]] ; Paterson, 2018).

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