Editing IPCC:AR6/WGII/Chapter-11 (section)

==== 11.3.4.1 Field Crops and Horticulture ====

<div id="h3-10-siblings" class="h3-siblings"></div>

<div id="11.3.4.1.1" class="h4-container"></div>

<span id="observed-impacts-3"></span>
===== 11.3.4.1.1 Observed impacts =====

<div id="h4-8-siblings" class="h4-siblings"></div>

Drought, heat and frost in recent decades have shown the vulnerability of Australian field crops and horticulture to climate change ( [[#Cai--2014|Cai et al., 2014]] ; [[#Howden--2014|Howden et al., 2014]] ; [[#CSIRO%20and%20BOM--2015|CSIRO and BOM, 2015]] ; [[#Lobell--2015|Lobell et al., 2015]] ; [[#Hughes--2017|Hughes and Lawson, 2017]] ; [[#King--2017|King et al., 2017]] ; [[#Webb--2017|Webb et al., 2017]] ; [[#Harris--2020|Harris et al., 2020]] ) as recognised by policymakers ( [[#CoA--2019a|CoA, 2019a]] ) ( ''high confidence'' ). Northern Australia’s agricultural output losses are on average 19% each year due to drought ( [[#Thi%20Tran--2016|Thi Tran et al., 2016]] ). In southern Australia, the frequency of frost has been relatively unchanged since the 1980s ( [[#Dittus--2014|Dittus et al., 2014]] ; [[#Pepler--2018|Pepler et al., 2018]] ; [[#BoM%20and%20CSIRO--2020|BoM and]] [[#CSIRO--2020|CSIRO, 2020]] ). Drier winters have increased the irrigation requirement for wine grapes ( [[#Bonada--2020|Bonada et al., 2020]] ), while smoke from the 2019/20 fires, which occurred early in the season, caused significant taint damage ( [[#Jiang--2021|Jiang et al., 2021]] ). In New Zealand, reduced winter chill has a compounded impact on the kiwifruit industry, resulting in early harvest and increased energy demand for refrigeration and port access problems ( [[#Cradock-Henry--2019|Cradock-Henry et al., 2019]] ) (11.5).

Across all types of agriculture, drought and its physical flow-on effects have caused financial and emotional disruption and stress in farm households and communities ( [[#Austin--2018|Austin et al., 2018]] ; [[#Bryant--2018|Bryant and Garnham, 2018]] ; [[#Yazd--2019|Yazd et al., 2019]] ) (11.3.6). Severe and uncertain climate conditions are statistically associated with increases in farmer suicide ( [[#Crnek-Georgeson--2017|Crnek-Georgeson et al., 2017]] ; [[#Perceval--2019|Perceval et al., 2019]] ). Rural women often carry extra stress and responsibilities, including increased unpaid and paid work and emotional load ( [[#Whittenbury--2013|Whittenbury, 2013]] ; [[#Hanigan--2018|Hanigan et al., 2018]] ; [[#Rich--2018|Rich et al., 2018]] ).

<div id="11.3.4.1.2" class="h4-container"></div>

<span id="projected-impacts-3"></span>
===== 11.3.4.1.2 Projected impacts =====

<div id="h4-9-siblings" class="h4-siblings"></div>

Australian crop yields are projected to decline due to hotter and drier conditions, including intense heat spikes ( ''high confidence'' ) ( [[#Anwar--2015|Anwar et al., 2015]] ; [[#Lobell--2015|Lobell et al., 2015]] ; [[#Prokopy--2015|Prokopy et al., 2015]] ; [[#Dreccer--2018|Dreccer et al., 2018]] ; [[#Nuttall--2018|Nuttall et al., 2018]] ; [[#Wang--2018a|Wang et al., 2018a]] ). Interactions of heat and drought could lead to even greater losses than heat alone ( [[#Sadras--2015|Sadras and Dreccer, 2015]] ; [[#Hunt--2018|Hunt et al., 2018]] ). Australian wheat yields are projected to decline by 2050, with a median yield decline of up to 30% in southwest Australia and up to 15% in southern Australia, with possible increases and decreases in the east ( [[#Taylor--2018|Taylor et al., 2018]] ; [[#Wang--2018a|Wang et al., 2018a]] ). In temperate fruit, accumulated winter chill for horticulture is projected to further decline ( [[#Darbyshire--2016|Darbyshire et al., 2016]] ). Winegrape maturity is projected to occur earlier due to warmer temperatures ( ''high confidence'' ) ( [[#Webb--2014|Webb et al., 2014]] ; [[#van%20Leeuwen--2016|van Leeuwen and Darriet, 2016]] ; [[#Jarvis--2018|Jarvis et al., 2018]] ; [[#Ausseil--2019b|Ausseil et al., 2019b]] ), leading to potential changes in wine style ( [[#Bonada--2015|Bonada et al., 2015]] ). Rice is susceptible to heat stress, and average grain yield losses across rice varieties range from 83% to 53% in experimental trials when heat stress is applied during plant emergence and grain fill stages ( [[#Ali--2019|Ali et al., 2019]] ). In Tasmania, wheat yields are projected to increase, particularly at sites presently temperature-limited ( [[#Phelan--2014|Phelan et al., 2014]] ).

New Zealand evidence on impacts across crops is very limited. Precipitation and temperature changes alone show minor effects on crop yield, and winter yields of some crops may increase (e.g., wheat, maize) ( [[#Ausseil--2019b|Ausseil et al., 2019b]] ). For temperate fruit, loss of winter chill may reduce yields in some regions and trigger impacts across supply chains ( [[#Cradock-Henry--2019|Cradock-Henry et al., 2019]] ) (11.5.1). Increased pathogens could damage the cut flower, guava and feijoa fruit growing and the honey and related industries ( [[#Lawrence--2016|Lawrence et al., 2016]] ). The combined effects of changes in seasonality, temperature, precipitation, water availability and extremes, such as drought, have the potential to escalate impacts, but understanding of these effects is limited.

Other climate-change-related factors complicate crop climate responses. When CO 2 was elevated from present-day levels of 400 to 550 ppm in trials, yields of rainfed wheat, field pea and lentil increased approximately 25% (0–70%). However, there was a 6% reduction in wheat protein that could not be offset by additional nitrogen fertilizer ( [[#O’Leary--2015|O’Leary et al., 2015]] ; [[#Fitzgerald--2016|Fitzgerald et al., 2016]] ; [[#Tausz--2017|Tausz et al., 2017]] ). Elevated CO 2 will worsen some pest and disease pressures, for example, barley yellow dwarf virus impacts on wheat ( [[#Trębicki--2015|Trębicki et al., 2015]] ). Warmer temperatures are also expanding the potential range of the Queensland fruit fly, including into New Zealand ( [[#Aguilar--2015a|Aguilar et al., 2015a]] ), threatening the horticulture industry ( [[#Sultana--2017|Sultana et al., 2017]] ; [[#Sultana--2020|Sultana et al., 2020]] ). Some crop pests (e.g., the oat aphid) are projected to be negatively affected by climate change ( [[#Macfadyen--2018|Macfadyen et al., 2018]] ), but so too are beneficial insects. There is large uncertainty in rainfall and crop projections for northern Australia (Table 11.3). For sugarcane, an impact assessment for CO 2 at 734 ppm using the A2 emission scenario at Ayr in Queensland projected modest yield increases ( [[#Singels--2014|Singels et al., 2014]] ). Climate change is projected to adversely impact tropical fruit crops such as mangoes through higher minimum and maximum temperatures, reducing the number of inductive days for flowering ( [[#Clonan--2020|Clonan et al., 2020]] ).

Climate change is projected to shift agro-ecological zones ( ''high confidence'' ) ( [[#Lenoir--2015|Lenoir and Svenning, 2015]] ; [[#Scheffers--2016|Scheffers et al., 2016]] ). This includes the climatically determined cropping strip bounded by the inner arid rangelands and the wetter coast or mountain ranges in mainland Australia ( [[#Nidumolu--2012|Nidumolu et al., 2012]] ; [[#Eagles--2014|Eagles et al., 2014]] ; [[#Tozer--2014|Tozer et al., 2014]] ). A narrowing of grain-growing regions is projected with a shift of the inner margin towards the coast under drier and warmer conditions ( [[#Nidumolu--2012|Nidumolu et al., 2012]] ; [[#Fletcher--2020|Fletcher et al., 2020]] ). The economic impact of the shift depends on adaptation ( [[#Sanderson--2015|Sanderson et al., 2015]] ; [[#Hunt--2019|Hunt et al., 2019]] ) and how resources, support industries, infrastructure and settlements adapt. Shifts in agro-ecological zones present some opportunities, for example warming is projected to be beneficial for wine production in Tasmania ( [[#Harris--2020|Harris et al., 2020]] ).

<div id="11.3.4.1.3" class="h4-container"></div>

<span id="adaptation-3"></span>
===== 11.3.4.1.3 Adaptation =====

<div id="h4-10-siblings" class="h4-siblings"></div>

Some farmers are adapting to drier and warmer conditions through more effective capture of non-growing-season rainfall (e.g., stubble retention to store soil water), improved water use efficiency and matching sowing times and cultivars to the environment ( ''high confidence'' ) ( [[#Kirkegaard--2011|Kirkegaard and Hunt, 2011]] ; [[#Fitzer--2019|Fitzer et al., 2019]] ; [[#Haensch--2021|Haensch et al., 2021]] ). Observed adaptations include new technologies that improve resource efficiencies, professional knowledge and skills development, new farmer and community networks and diversification of business and household income ( [[#Ghahramani--2015|Ghahramani et al., 2015]] ; [[#De--2016|De et al., 2016]] ). For Australian wheat, earlier sowing and longer-season cultivars may increase yield by 2–4% by 2050, with a range of −7 to +2% by 2090 ( [[#Wang--2018a|Wang et al., 2018a]] ). In the wheat industry, breeding for improved reproductive frost tolerance remains a priority ( [[#Lobell--2015|Lobell et al., 2015]] ). Modelling suggests that, since 1990, farm management has held Australian wheat yields constant, but declining rainfall and increasing temperature may have contributed to a 27% decline in simulated potential Australian wheat yield ( [[#Hochman--2017|Hochman et al., 2017]] ).

Other observed incremental adaptations include later pruning in the grape industry to spread harvest period and partially restore wine balance, with neutral effects on yield and cost ( [[#Moran--2019|Moran et al., 2019]] ; [[#Ausseil--2021|Ausseil et al., 2021]] ). The cotton sector increasingly requires shifts in sowing dates to avoid financial impacts ( [[#Luo--2017|Luo et al., 2017]] ). During years of low water availability, rice growers have been trading water and/or shifting to dry land farming ( [[#Mushtaq--2016|Mushtaq, 2016]] ).

Growers in New Zealand are changing the timing of their operations, growing crops within covered enclosures and purchasing insurance ( [[#Cradock-Henry--2015|Cradock-Henry and McKusker, 2015]] ) Teixeira et al. 2018). Investment of capital in irrigation infrastructure has increased ( [[#Cradock-Henry--2018a|Cradock-Henry et al., 2018a]] ), although its effectiveness as an adaptation depends on water availability (Box 11.5). In industries based on long-lived plants, such as the kiwifruit and grape industries, many of the adaptations (e.g., breeding and growing heat-adapted and disease-resistant varieties) have long lead times and require greater investment than in the cropping sector ( [[#Cradock-Henry--2020a|Cradock-Henry et al., 2020a]] ). While breeding programmes for traits with enhanced resilience to future climates are beginning, there is little evidence of strategic industry planning ( [[#Cradock-Henry--2018a|Cradock-Henry et al., 2018a]] ).

For drought management, balancing near-term needs with long-term adaptation to increasing aridity is essential ( [[#Downing--2016|Downing et al., 2016]] ). Insufficient and maladaptive decisions can have far-reaching effects, including changes to resources, infrastructure, services and supply chains to which others must adapt ( [[#Fleming--2015|Fleming et al., 2015]] ; [[#Graham--2018|Graham et al., 2018]] ). While there is potential for a greater proportion of agriculture to be located to northern Australia, there are significant and complex agronomic, environmental, institutional, financial and social challenges for successful transformation, including the risk of disruption ( ''medium confidence'' ) ( [[#Jakku--2016|Jakku et al., 2016]] ).

<div id="11.3.4.2" class="h3-container"></div>

<span id="livestock"></span>