Effects of climate change on livestock
There are numerous interlinked effects of climate change on livestock rearing. This activity is both heavily affected by and a substantial driver of anthropogenic climate change due to its greenhouse gas emissions. As of 2011, some 400 million people relied on livestock in some way to secure their livelihood.[3]: 746 The commercial value of this sector is estimated as close to $1 trillion.[4] As an outright end to human consumption of meat and/or animal products is not currently considered a realistic goal,[5] any comprehensive adaptation to effects of climate change must also consider livestock.
The observed adverse impacts on
While some areas which currently support livestock animals are expected to avoid "extreme heat stress" even with high warming at the end of the century, others may stop being suitable as early as midcentury.
Proposed adaptations to climate change in livestock production include improved cooling at animal shelters and changes to animal feed, though they are often costly or have only limited effects.
Heat stress in livestock
Projected worldwide increases
In general, the preferred ambient temperature range for domestic animals is between 10 and 30 °C (50 and 86 °F).
In Jamaica, considered representative of the Caribbean region, all livestock animals besides layer hens are already exposed to "very severe" heat stress in the present climate, with pigs being exposed to it at least once per day during the 5 summer and early autumn months, while ruminants and broilers only avoid daily exposure to very severe heat stress during the winter. it has been projected that even at 1.5 °C (2.7 °F) of global warming, "very severe" heat stress would become a daily event for ruminants and broilers. By 2 °C (3.6 °F), it would be felt for a longer duration, and extensive cooling systems would likely become a necessity for livestock production in the Caribbean. At 2.5 °C (4.5 °F), only layer hens would avoid daily exposure to "very severe" heat stress during the winter months.[12]
Studies of heat stress and livestock had historically focused on cattle, as they are often kept outdoors and so are immediately exposed to changes in climate. On the other hand, a little over 50% of all pork production and 70% of all poultry production worldwide originated from animals kept entirely in confined buildings even around 2006, and the raw numbers were expected to increase by 3–3.5 times for pigs, by 2–2.4 times for
Health impacts of heat stress
Once the body temperature of livestock animals is 3–4 °C (5.4–7.2 °F) above normal, this soon leads to "
Livestock can also suffer multiple sublethal impacts from heat stress, such as reduced milk production. Once the temperatures exceed 30 °C (86 °F), cattle, sheep, goats, pigs and chickens all begin to consume 3–5% less feed for each subsequent degree of temperature increase.
The immune system is also known to be impaired in heat-stressed animals, rendering them more susceptible to various infections.[2] Similarly, vaccination of livestock is less effective when they suffer from heat stress.[16] So far, heat stress had been estimated by researchers using inconsistent definitions, and current livestock models have limited correlation with experimental data.[17] Notably, since livestock like cows spend much of their day laying down, comprehensive heat stress estimation needs to take account of ground temperature as well,[18] but the first model to do so was only published in 2021, and it still tends to systematically overestimate body temperature while underestimating breathing rate.[19]
Economic impact and adaptation
In the United States alone, economic losses caused by heat stress in livestock were already valued at between $1.69 and $2.36 billion in 2003, with the spread reflecting different assumptions about the effectiveness of contemporary adaptation measures.[20] Nevertheless, some reviews consider the United States to be the least vulnerable nation to food security shocks caused by the negative impacts of climate change on livestock, as while it rates in the middle of the pack in terms of exposure of its livestock and the societal sensitivity to that exposure, it has the highest adaptive capacity in the world due to its GDP and development status. Japan and the nations in Europe have low vulnerability for similar reasons.
Meanwhile the exposure of Mongolian livestock to climate change is not very different from that of American livestock, but the enormous importance of pastoralism in Mongolian society and its limited capacity to adapt still renders it one of the most vulnerable countries in the world. Nations in sub-Saharan Africa generally suffer from high exposure, low adaptive capacity and high sensitivity due to the importance of livestock in their societies, with these factors particularly acute in Eastern African countries,[1] where between 4 and 19% of livestock-producing areas are expected to suffer "significantly" more "dangerous" heat stress events after 2070, depending on the climate change scenario.[21] There is high confidence that under the most intense scenario, SSP5-8.5, the net amount of land which can support livestock will decline by 2050 as heat stress would already become unbearable for them in some locations.[3]: 748
A range of climate change adaptation measures can help to protect livestock, such as increasing access to drinking water, creating better shelters for animals kept outdoors and improving air circulation in the existing indoor facilities.[22] Installing specialized cooling systems is the most capital-intensive intervention, but it may be able to completely counteract the impact of future warming.[8]
Difficulties in feeding livestock
Climatic impacts on feed and forage
Livestock is fed either by letting them directly graze
Climate change can impact livestock animals' food supply in multiple ways. First, the direct effects of temperature increase affect both fodder cultivation and productivity of rangelands, albeit in variable ways. On a global scale, there is confidence that with all else equal, every single 1 °C (1.8 °F) of warming would decrease the yields of the four most important crops by between ~3% for rice and
While climate change increases precipitation on average, regional changes are more variable, and variability alone adversely impacts "animal fertility, mortality, and herd recovery, reducing livestock keepers' resilience".[3]: 717 In Zimbabwe, uncertainty about rainfall under different climate change scenarios could mean the difference between 20% and 100% of farmers negatively affected by 2070, while the average livestock revenue could potentially increase by 6%, yet may also plunge by as much as 43%.[31]
Many places are likely to see increased drought, which would affect both the crops and the pastural land.
Atmospheric CO2 and livestock forage
The abundance of fodder and forage strongly benefits from the
Warming and water deficit also affect nutritional value, sometimes synergistically. For instance,
Global impacts of lowered livestock nutrition
Altogether, around 10% of current global pasture is expected to be threatened by water scarcity caused by climate change, as early as 2050.[30]: 614 By 2100, 30% of the current combined crop and livestock areas would become climatically unsuitable under the warmest scenario SSP5-8.5, as opposed to 8% under the low-warming SSP1-2.6, although neither figure accounts for the potential shift of production to other areas.[3]: 717 If 2 °C (3.6 °F) of warming occurs by 2050, then 7–10% of the current livestock are predicted to be lost primarily due to insufficient feed supply, amounting to $10–13 billion in lost value.[3]: 748
Similarly, an older study found that if 1.1 °C (2.0 °F) of warming occurs between 2005 and 2045 (rate comparable to hitting 2 °C (3.6 °F) by 2050), then under the current livestock management paradigm, global agricultural costs would increase by 3% (an estimated $145 billion), with the impact concentrated in pure pasturalist systems. At the same time, mixed crop-livestock systems already produced over 90% of the global milk supply as of 2013, as well as 80% of ruminant meat,[43] yet they would bear the minority of the costs, and switching all pure livestock systems to mixed crop-livestock would decrease global agricultural costs from 3% to 0.3%, while switching half of those systems would reduce costs to 0.8%. The full shift would also reduce future projected deforestation in the tropics by up to 76 million ha.[42]
Pathogens and parasites
While climate-induced heat stress can directly reduce domestic animals' immunity against all diseases,
Temperature increases are also likely to benefit
The impacts of climate change on
By type of livestock
Aquaculture
Under high warming, there will be a global decline in area suitable for
Camels
Along with camels, goats are more resilient to drought than cattle. In Southeastern Ethiopia, some of the cattle pastoralists are already switching to goats and camels.[49]
Cattle
As of 2009, there were 1.2 billion cattle in the world, with around 82% in the
Heatwaves can also reduce milk yield, with particularly acute impacts if the heatwave lasts for four or more days, as at that point the cow's thermoregulation capacity is usually exhausted, and its core body temperature starts to increase.
Cattle are suspectible to some specific heat stress risks, such as
One of the vectors of bacteria which cause mastitis are
By 2017, it was already reported that farmers in Nepal kept fewer cattle due to the losses imposed by a longer hot season.
As of 2022, it has been suggested that every additional millimeter of annual precipitation increases beef production by 2.1% in the tropical countries and reduces it by 1.9% in temperate ones, yet the effects of warming are much larger. Under SSP3-7.0, a scenario of significant warming and very low adaptation, every additional 1 °C (1.8 °F) would decrease global beef production by 9.7%, mainly because of its impact on tropical and poor countries. In the countries which can afford adaptation measures, production would fall by around 4%, but by 27% in those which cannot.[68] In 2024, another study suggested that the impacts would be milder - a 1% decrease per every additional 1 °C (1.8 °F) in low-income countries and 0.2% in high-income ones, and a 3.2% global decline in beef production by 2100 under SSP3-7.0.[7] The same paper suggests that out of the top 10 beef-producing countries (Argentina, Australia, Brazil, China, France, India, Mexico, Russia, Turkey and the U.S.), only China, Russia and the U.S. would see overall production gains with increased warming, with the rest experiencing declines.[7] Other research suggests that east and south of Argentina may become more suitable to cattle ranching due to climate-driven shifts in rainfall, but a shift to Zebu breeds would likely be needed to minimize the impact of warming.[69]
Equines
As of 2019, there are around 17 million horses in the world. Healthy body temperature for adult horses is in the range between 37.5 and 38.5 °C (99.5 and 101.3 °F), which they can maintain while ambient temperatures are between 5 and 25 °C (41 and 77 °F). However, strenuous exercise increases core body temperature by 1 °C (1.8 °F)/minute, as 80% of the energy used by equine muscles is released as heat. Along with
Goats and sheep
Goats and sheep are often collectively described as small ruminants, and tend to be studied together rather than separately.[75] Both of them are known to be less affected by climate change than cattle,[3]: 747 with goats in particular considered one the most climate-resilient domestic animals, being second only to camels.[76] In Southeastern Ethiopia, some of the cattle pastoralists are already switching to goats and camels.[49]
Even so, the 2007–2008 drought in Iran had already resulted in the country's sheep population declining by nearly 4 million – from 53.8 million in 2007 to 50 million in 2008, while the goat population declined from 25.5 million in 2007 to 22.3 million in 2008.[25] Some researchers expect climate change to drive genetic selection towards more heat- and drought-adapted breeds of sheep.[77] Notably, heat-adapted sheep can be of both wool and hair breeds, in spite of the popular perception that hair breeds are always more resistant to heat stress.[78]
Parasitic worms
Pigs
For pigs, heat stress varies depending on their age and size. Young and growing pigs with the average body mass of 30 kg (66 lb) can tolerate temperatures up to 24 °C (75 °F) before starting to experience any heat stress, but after they have grown and are fattened to about 120 kg (260 lb), at which point they are considered ready for slaughter, their tolerance drops to just 20 °C (68 °F).[8]
One paper estimated that in Austria, at an intensive farming facility used to fatten up about 1800 growing pigs at a time, the already observed warming between 1981 and 2017 would have increased relative annual heat stress by between 0.9 and 6.4% per year. It is considered representative of other such facilities in Central Europe.[13]
A follow-up paper considered the impact of several adaptation measures. Installing a
Poultry
It is believed that the thermal comfort zone for poultry is in the 18–25 °C (64–77 °F) range. Some papers describe 26–35 °C (79–95 °F) as the "critical zone" for
Around 2003, it was estimated that the poultry industry in the United States already lost up to $165 million annually due to heat stress at the time.[80] One paper estimated that if global warming reaches 2.5 °C (4.5 °F), then the cost of rearing broilers in Brazil increases by 35.8% at the least modernized farms and by 42.3% at farms with the medium level of technology used in livestock housing, while they increase the least at farms with the most advanced cooling technologies. On the contrary, if the warming is kept to 1.5 °C (2.7 °F), costs at moderately modernized farms increase the least, by 12.5%, followed by the most modernized farms with a 19.9% increase, and the least technological farms seeing the greatest increase.[92]
Reindeer
By mid-2010s, indigenous people of the Arctic have already observed reindeer breeding less and surviving winters less often, as warmer temperatures benefit biting insects and result in more intense and persistent swarm attacks. They also become more susceptible to parasites spread by such insects, and as the Arctic becomes warmer and more accessible to invasive species, it is anticipated that they will come in contact with pests and pathogens they have not encountered historically.[44]: 233
Greenhouse gas emissions from livestock activities
Livestock produces the majority of greenhouse gas emissions from agriculture and demands around 30% of agricultural fresh water needs, while only supplying 18% of the global calorie intake. Animal-derived food plays a larger role in meeting human protein needs, yet is still a minority of supply at 39%, with crops providing the rest.[3]: 746–747
Out of the
Livestock and livestock-related activities such as deforestation and increasingly fuel-intensive farming practices are responsible for over 18%[95] of human-made greenhouse gas emissions, including:
- 9% of global carbon dioxide emissions
- 35–40% of global methane emissions (chiefly due to enteric fermentation and manure)
- 64% of global nitrous oxide emissions (chiefly due to fertilizer use.[95])
Livestock activities also contribute disproportionately to land-use effects, since crops such as corn and alfalfa are cultivated in order to feed the animals.
In 2010, enteric fermentation accounted for 43% of the total greenhouse gas emissions from all agricultural activity in the world.[96] The meat from ruminants has a higher carbon equivalent footprint than other meats or vegetarian sources of protein based on a global meta-analysis of lifecycle assessment studies.[97] Small ruminants such as sheep and goats contribute approximately 475 million tons of carbon dioxide equivalent to GHG emissions, which constitutes around 6.5% of world agriculture sector emissions.[98] Methane production by animals, principally ruminants, makes up an estimated 15-20% global production of methane.[99][100] Research continues on the use of various seaweed species, in particular Asparegopsis armata, as a food additive that helps reduce methane production in ruminants.[101]
Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.[95] The way livestock is grazed also affects future fertility of the land. Not circulating grazing can lead to unhealthy compacted soils. The expansion of livestock farms affects the habitats of native wildlife and has led to their decline. Reduced intake of meat and dairy products is another effective approach to reduce greenhouse gas emissions. Slightly over half of Europeans (51%) surveyed in 2022 support reducing the amount of meat and dairy products people may buy to combat climate change - 40% of Americans and 73% of Chinese respondents felt the same.[102]See also
- Economic impacts of climate change
- Effects of climate change on agriculture
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