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

==== 11.3.4.2 Livestock ====

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===== 11.3.4.2.1 Observed impacts =====

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Both the seasonality and annual production of pasture is changing ( ''high confidence'' ). In many regions, warming is increasing winter pasture growth ( [[#Lieffering--2016|Lieffering, 2016]] ); the effects on spring growth are more mixed, with some regions experiencing increased growth ( [[#Newton--2014|Newton et al., 2014]] ) and others experiencing reduced spring growth ( [[#Perera--2020|Perera et al., 2020]] ). Droughts are causing economic damage to livestock enterprises, with drought and market prices significantly affecting profit ( [[#Hughes--2019a|Hughes et al., 2019a]] ), in addition to the impacts on animal health and the livelihoods of pastoralists, periods of drought contribute to land degradation, particularly in the cattle regions of northern Australia ( [[#Marshall--2015|Marshall, 2015]] ). Heat load in cattle leads to reduced growth rates and reproduction, and extreme heat waves can lead to death ( [[#Lees--2019|Lees et al., 2019]] ; [[#Harrington--2020|Harrington, 2020]] ). Temperatures over 32°C reduce ewe and ram fertility along with the birth weight of lambs ( [[#van%20Wettere--2021|van Wettere et al., 2021]] ).

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===== 11.3.4.2.2 Projected impacts =====

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Some areas may experience increased pasture growth, but others may experience a decrease that cannot be fully offset by adaptation ( ''high confidence'' ) ( [[#Moore--2013|Moore and Ghahramani, 2013]] ; [[#Lieffering--2016|Lieffering, 2016]] ; [[#Kalaugher--2017|Kalaugher et al., 2017]] ). Climate change may modify the seasonality of pasture growth rates more than annual yields in New Zealand ( [[#Lieffering--2016|Lieffering, 2016]] ). In eastern parts of Queensland, climate change impacts on pasture growth are equivocal, with simple empirical models suggesting a decrease in net primary productivity ( [[#Liu--2017|Liu et al., 2017]] ), while mechanistic models that include increases in length of the growing season and the beneficial effects of CO 2 fertilisation indicate increases in pasture growth ( [[#Cobon--2020|Cobon et al., 2020]] ). In Tasmania, annual pasture production is projected to increase by 13–16%, even with summer growth projected to decline with increased interannual variability, resulting in a projected increase in milk yields by 3–16% per annum ( [[#Phelan--2015|Phelan et al., 2015]] ).

Extreme climatic events (droughts, floods and heatwaves) are projected to adversely impact productivity for livestock systems ( ''medium confidence'' ). This includes reduced pasture growth rates between 3–23% by 2070 from late spring to autumn and elevated growth in winter and early spring ( [[#Cullen--2009|Cullen et al., 2009]] ; [[#Hennessy--2016|Hennessy et al., 2016]] ; [[#Chang-Fung-Martel--2017|Chang-Fung-Martel et al., 2017]] ). Heavy rainfall and storms are projected to lead to increased erosion, particularly in extensively grazed systems on steeper land, reducing productivity for decades, reducing soil carbon ( [[#Orwin--2015|Orwin et al., 2015]] ) and increasing sedimentation. Increased heat stress in livestock is projected to decrease milk production and livestock reproduction rates ( ''high confidence'' ) ( [[#Nidumolu--2014|Nidumolu et al., 2014]] ; [[#Ausseil--2019b|Ausseil et al., 2019b]] ; [[#Lees--2019|Lees et al., 2019]] ). In Australia, the average number of moderate to severe heat stress days for livestock is projected to increase 12–15 d by 2025 and 31–42 d by 2050 compared to 1970–2000 ( [[#Nidumolu--2014|Nidumolu et al., 2014]] ). In New Zealand, an extra 5 (RCP2.6) to 7 (RCP8.5) moderate heat stress days per year are projected for 2046–2060 ( ''high confidence'' ) ( [[#Ausseil--2019b|Ausseil et al., 2019b]] ), which would especially affect animals transported long distances ( [[#Zhang--2019|Zhang and Phillips, 2019]] ) and strain the cold chains needed to deliver meat and dairy products safely. The distribution of existing and new pests and diseases are projected to increase, for example, new tick- and mosquito-borne diseases such as bovine ephemeral fever ( [[#Kean--2015|Kean et al., 2015]] ).

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===== 11.3.4.2.3 Adaptation =====

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Adaptations in both grazing and confined beef cattle systems require enhanced decision-making skills capable of integrating biophysical, social and economic considerations ( ''high confidence'' ). Social learning networks that support integration of lessons learned from early adopters and involvement with science-based organisations can help enhance decision-making and climate adaptation planning ( [[#Derner--2018|Derner et al., 2018]] ). Pasture management adaptations for livestock production include deeper rooted pasture species in higher rainfall regions ( [[#Cullen--2014|Cullen et al., 2014]] ) and drought-tolerant species ( [[#Mathew--2018|Mathew et al., 2018]] ). Soil and land management practices are important in ensuring soils maintain their supporting and regulating services ( [[#Orwin--2015|Orwin et al., 2015]] ). Adaptations in the primary sector in New Zealand are now positioned within the requirements of the National Policy Statement on Freshwater ( [[#MfE--2020b|MfE, 2020b]] ). Adaptations to manage heat stress in livestock include altering the breeding calendar, providing shade and sprinklers, altering nutrition and feeding times and more heat-tolerant animal breeds ( [[#Chang-Fung-Martel--2017|Chang-Fung-Martel et al., 2017]] ; [[#Lees--2019|Lees et al., 2019]] ; [[#van%20Wettere--2021|van Wettere et al., 2021]] ).

Beef rangeland systems in Queensland are projected to have benefits in the southeast through higher CO 2 and temperatures extending the growing season and reducing frost, but a warmer and drier climate in the southwest may reduce pasture and livestock production ( [[#Cobon--2020|Cobon et al., 2020]] ). Northern Queensland is most resilient to temperature and rainfall changes (production limited by soil fertility) while western/central west Queensland is most sensitive to rainfall changes, that is, low rainfall is associated with lower productivity ( [[#Cobon--2020|Cobon et al., 2020]] ). The social context of climate change impacts and the processes shaping vulnerability and adaptation, especially at the scale of the individual, are critical to successful adaptation efforts ( [[#Marshall--2014|Marshall and Stokes, 2014]] ).

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