The Fifth National Climate Assessment (NCA5) was released on November 14, 2023. Assembled by teams of researchers from a range of climate change specialties, the publication represents a synthesis of current research including an evaluation of the current and future implications of climate change for life in the United States. As those paying attention to agriculture know, climate impacts have become increasingly apparent since the last assessment was published in 2018.
As with recent reports from the Intergovernmental Panel on Climate Change, the NCA5 presents a grim overall outlook with substantial climate shifts observed and predicted around the country. However, the publication also presents planned solutions to reduce emissions and transform toward increasingly robust farming systems.
The NCA5 covers a lot of ground, but this summary focuses on aspects most relevant to agriculture. The primary message regarding agriculture as a whole is that the risks to agricultural production are rising and will continue to rise as a result of climate change. The authors rank this evaluation as “very likely” with “very high confidence” of its accuracy. Despite the challenges ahead, substantial reason for optimism lies both in suggested routes to emissions reductions and adaptation of farming systems.
Table of Contents
Some of the clearest reasons for concern about impacts on agriculture are laid out in the chapter on water. For example, increasing aridity in the Southwest and increasingly wet conditions throughout the northeast regions of the country–from the Midwest through New England–are likely to challenge crop and livestock production. Drought and torrential rain will frequently reduce productivity in all regions. Despite wetter conditions in parts of the country, researchers expect higher temperatures to reduce overall soil moisture in most regions. Climatic water deficit, a measure of how much water plants lack to meet their needs, gives an overall sense of the country’s water outlook. Particularly acute deficits are expected in much of the country east of the 100th meridian.
Along with these changes, USDA plant hardiness zones will continue to shift as temperatures continue to rise. Species and varieties that once functioned well in a given area may no longer be adapted to the warmer temperatures they experience as the climate changes.
The agriculture chapter notes that all dimensions of food security will be affected by climate change and that crop insurance costs have already risen in response to increased losses. Moreover, despite a steady growth in total factor productivity (TFP, “a ratio of agricultural outputs produced to inputs used“) since 1948 as a result of technological change, climate change has already dampened TFP, and it is expected to decline to pre-1980 levels by 2050 unless adaptation measures adequately respond. Because of increased crop specialization in the Midwest, TFP has become more sensitive to the increasing summer temperatures and moisture deficits. In short, much of the current system is more susceptible to climate impacts because of current monocultural agricultural practices.
Although there are clear, negative impacts for agriculture, the agriculture chapter effectively lays out the ways in which agriculture can respond constructively to increasing challenges. The authors identify the continued risks presented by “excessive tillage, overgrazing, and over reliance on agrochemicals.” In response, the chapter centers agroecological solutions like enhanced soil health and diversified landscapes. This focus represents a noticeable shift from the Fourth Assessment, where “climate-smart” solutions focused on improved technologies (e.g., high-efficiency irrigation and genetic modification) rather than systems approaches.
However, solutions to livestock methane center on feed supplements and energy capture from liquid manure systems rather than grazing systems. The authors do not discuss the advantages of highly-managed pasture carbon sequestration outweighing the emissions of associated livestock. So, unfortunately, the increased systems approach of the chapter is not applied across all agricultural issues. On the other hand, the chapter’s assessment of alternative plant proteins is more measured, noting their potential to reduce greenhouse gas emissions but also identifying the clear downsides in terms of increased needs for infrastructure and energy.
Another way in which NCA5 represents an advancement upon NCA4 is its strong discussions around environmental justice. The agriculture chapter’s Key Message 2, “Climate Change Disrupts Our Food System in Uneven Ways,” puts worsening heat stress among farm workers front and center. The authors also note ongoing and increasing “disruptions to the ability of subsistence-based peoples to access food through hunting, fishing, and foraging.” In addition to laying out the ways in which social and economic factors make some segments of society more vulnerable, though, the chapter also demonstrates the ways in which many of the same populations are developing their own solutions–e.g., the Osage Nation’s community orchard.
Beyond the agriculture chapter, each of the regional chapters also puts a spotlight on both the inequities built into U.S. systems and on the ways in which overburdened communities are identifying and building out unique solutions.
In the Northern Great Plains, for example, Box 25.3 frames adaptation successes like the Tanka Fund and the InterTribal Buffalo Council bringing back the buffalo. Other successes include better soil health management practices as a result of federal spending and restoration of native perennial cover as in programs like the Audubon Great Plains Conservation Forage Program.
These are important given the challenges the region is already experiencing. Increased aridity, warmer winter nights, shifts in the timing of precipitation, more intense precipitation events, more droughts, more and larger hail, declining streamflow, pollinator decline, and longer fires are some of the steep challenges brought by climate change.
Although some impacts of climate change may be positive as with carbon enrichment leading to greater net primary productivity in pastures, opposite forces often act at the same time–as with the reductions in forage nutritional quality that result alongside increased warming.
The Northern Great Plains chapter notes that current water rights laws in much of the region make adaptation especially difficult. Colorado is working on plans that would increase flexibility of the system, although change has been challenging. Among the most important needs for the region is increased use of data in decision-making. Incorporating weather data into rangeland planning is one example offered.
In the Northeast, droughts, floods, and heatwaves are among some of the most significant impacts seen. In this region, fisheries are an important livelihood in the food system, and the authors note that fish stocks are shifting northeastward into deeper waters. Some species are also declining, further straining local livelihoods. Sea level rise is also important in the region, causing saltwater intrusion and salinization.
Changes like sea level rise are resulting in the loss of culturally significant locations for subsistence harvesting. These shifts raise the importance of maintaining access to culturally important locations regardless of whether they are inundated by rising seas.
The Southeast chapter has a stronger focus on agriculture than the Northeast chapter, but focuses on less systems-based solutions, such as precision agriculture and genetically modified organisms. However, organic production, silvopasture, agroforestry and “other agroecological systems” are also listed among solutions.
Among the challenges highlighted for the Southeast are sea level rise and consequent saltwater intrusion (a notable issue in states like North Carolina), as well as the Southeast’s increasing droughts. Further, authors note the health and livelihood impacts on outdoor workers as a result of rising heat. The Southeast is one of the regions most affected by heatwaves. Hurricanes also present ever greater challenges, for example, Hurricane Florence whose heavy flooding left parts of the region covered in hog waste. The disproportionate impact of climate change on BIPOC communities and on lower-resourced small acreage farms is among the issues the chapter identifies as important for the Southeast to resolve.
The Caribbean chapter focuses on the U.S., including Puerto Rico and the U.S. Virgin Islands (U.S.V.I.). Daily average temperatures in the region are increasing. Puerto Rico has no clear trend in rainfall except overall annual reduction by the end of this century and more drought. Other risks include increasing tropical cyclones and sea level rise.
Unfortunately, the exclusion of Puerto Rico and the Virgin Islands from many data collection processes limits the ability of decision-makers in the region to understand and adapt to climate change. Nonetheless, it is clear that more extreme weather and the region’s high dependence on imported food (80% for Puerto Rico, 90% for the U.S.V.I.) will leave the area increasingly vulnerable. High crop losses from recent hurricanes, including Maria in 2017, resulted not only from direct impacts from the storms but also from related energy, telecom and water supply outages along with damage to roads and irrigation systems.
Higher temperatures can stress both crops and livestock. In fact, livestock are more vulnerable than they might be because many breeds have been imported from the U.S. mainland, and are more adapted to mainland conditions.
Crop insurance, such as that provided by the Puerto Rico Crop Insurance Corporation (PRCIC), offers protection. However, 98% of PRCIC payouts in the last decade were from hurricanes, highlighting the steep adaptive needs presented by storms. In addition, the program does not cover the increasing challenge of drought.
Along with the Northern Plains, the Midwest chapter has one of the strongest foci on agriculture of all the regional chapters. Among the challenges named for these states are increasing temperatures and oscillations between extremes. “Changes in precipitation extremes, timing of snowmelt, and early-spring rainfall” will also increasingly require adaptations to production in the region. Higher summer temperatures have stressed crops, while higher lows in the winter have meant damage to perennial forage. Although carbon dioxide enrichment and warmer, wetter temperatures may increase forage growth, that is likely to be accompanied by a decrease in forage quality. Among the impacts to livestock will be feed shortages, loss of shade structures, and disease. Specialty crops have seen impacts from damaging spring frosts after earlier flowering, excessive moisture, and pollinator declines. For workers and crops, extreme heat is of ever-greater concern. Wildfire smoke from this region and others also poses risks to outdoor workers.
As a consequence of changes so far, crop insurance losses have risen. They are highest from drought, but the wet losses are increasing. Although drought overall has declined in the region since 1895, flash drought is becoming more common.
Change is “accelerating the loss of beings, access, and connection to the land for Indigenous Peoples,” including changes to sugar maples, and to access to activities like fishing. Adaptive moves like changing to other species, such as from maple to birch, may be limited because of the importance of cultural ties to certain species.
In the Southern Great Plains, temperatures and precipitation have increased across most of the region, except in Texas where only temperatures have increased. Days with heavy precipitation have become more frequent, and tropical storms present rising challenges. Droughts are a particular challenge, as in Kansas where there were droughts in 56 of 156 months from 2010 to 2022. For Oklahoma, it was 69 and for Texas 82 of those months.
The consequent impacts on agriculture include longer growing seasons, but also high temperatures that inhibit plant growth. With cold fronts combining with earlier springs, there has been more bud burst in perennial crops. Moreover, hot, dry, windy conditions present particularly deep challenges to both crops and livestocks especially with more frequent and intense droughts predicted going forward. Droughts are reducing rangeland quality and forcing owners to sell livestock, even as heatwaves and hot, dry, windy conditions also reduce livestock numbers.
One adaptive measure for these conditions is irrigation. State policies here tend to encourage consumptive use, do not account for the interactions between ground and surface water, and are overseen by multiple agencies. So, water solutions for a region with declining groundwater are especially difficult to assemble.
Restoration and adaptation actions include the work of Tribes. The Tribal Alliance for Pollinators is preserving grassland ecosystems. The Chickasaw Nation is teaming up with area land managers to remove invasive species, reduce fertilizer use, and restore habitat.
Annual average temperatures are rising in the Northwest, and have risen almost 2℉ since 1900. At the same time, cold nights have declined. A 10℉ rise in temperatures is expected for the century under high emissions conditions. So, snowpack will decline along with summer precipitation, and more drought is to be expected. Summer streamflows will be lower, and glaciers will continue to recede. Increased wildfire will also accompany these changes. Extreme events in the Northwest will include storms resulting from atmospheric rivers over the Pacific Ocean. With rising sea levels and warming ocean temperatures, heatwaves and high-temperature toxins (e.g., domoic acid) will harm sea life as well as anadromous species like salmon.
Agricultural systems in the Northwest will experience less chill accumulation as well as sunburn to fruit. Rising pest pressure, wildfire smoke, and drought are also concerns–already in 2020 and 2021 wheat and barley declined in yield as a result of droughts. Consequently, less forage is likely to be available. Some solutions offered include grass banks for pasture areas experiencing drought as well as temporary leasing of water.
The authors note that climate change affects stability and sense of place in regard to livelihoods, recreation, and Tribal traditions. However, Indigenous knowledge can also help with adaptation. They note, in particular, the importance of Tribal landscape management practices like prescribed burns.
The first key message for the Southwest is, “drought and increasing aridity threaten water resources.” The megadrought that began in 2000, making the early part of this century the driest period for the region in 1200 years, has clear links to declines in snowpack, reduced soil moisture, increased vegetation stress, and reduced reservoir levels. Despite these drying trends, the Southwest, like other regions, is experiencing floods from both unusually rapid snowmelt and brief but heavy precipitation events. Although much of the region is inland, the long coast of California is further strained by marine heatwaves, sea level rise, harmful algal blooms, and ocean acidification.
The ocean trends affect the species composition of the seas. Some species are seeing lower abundance, and the nutritional quality of some fish is reduced by conditions like harmful algal blooms. Along with fish and shellfish, marine heatwaves have affected ocean plantlife. Bull kelp experienced 90% losses in one heat wave, causing major losses to fisheries.
In addition, challenges to land-based food and fiber production have included a range of changes that are only expected to continue. Average minimum air temperature, growing degree days, and days above 86℉ are all increasing. These shift plant hardiness zones northward, expand the areas of heat stress, and create longer growing seasons not just for crops, but for pests, as well. Warmer winters also decrease needed chilling hours, and false springs increase plant vulnerability to freezes. Meanwhile, severe drought has posed substantial risks to both those with rain-fed crops and rangeland livestock. The hot conditions have also degraded living desert soil crusts, thereby increasing dangerous airbourne dust and accompanying diseases, such as coccidioidomycosis. The latter poses significant risks to outdoor workers, in particular.
Severe heat stress has reduced production of crops like Arizona upland cotton.The 2021 drought is estimated to have had $1.28 billion worth of impacts on crop production. Almonds, wine grapes, and other high value crops are among those affected.
Some adaptation measures, like locality-specific irrigation and site management like cover crops and fallowing can help, including with groundwater recharge. However, fallowing may also increase dust and weeds. With irrigated crops increasing, the uncertainty of irrigation water makes the system more vulnerable. Moreover, crop insurance acts as a disincentive to adapt to changing conditions, even though it helps farmers on a temporary basis. Colorado is experimenting with water transfers that would have minimal impact on rural areas, but implementation has been hampered by distrust.
As in other regions, the impacts are distributed disproportionately, with Indigenous populations especially affected by struggles with water availability. Urban food production has been offered as one route to decreasing food insecurity, but it often does not reach low-income communities. With rising hospitalizations and fatalities from heat and more airborne pollution (including wildfire smoke), the vulnerabilities of outdoor workers are increasing.
In addition, distrust of experts and financial costs slow the uptake of potential adaptation solutions on farms. Ranching decisions frequently exclude climate change-related information. In addition, some solutions may be hard for small acreage farmers to adopt because of expense. Furthermore, needed irrigation efficiencies are often complex to implement.
Fortunately, a focus on agroecological solutions has been gaining some traction. Reducing soil disturbance, increasing soil cover with cover cropping, reduced and no tillage solutions have all gained more attention.
Decision-makers increasingly recognize the importance of Indigenous knowledge solutions and of protecting and applying diverse knowledge systems as part of the pathway forward. The increased centering of “inclusive, participatory, and collaborative” problem solving offers some pathways forward.
With the Arctic warming much more rapidly than the continental US and substantial dependence on rural livelihoods, climate change presents particularly steep challenges to the state. Fishing, subsistence activities, and agriculture are all important food-related work experiencing significant effects from warming average temperatures. As glaciers shrink, permafrost thaws, sea ice declines, ocean water acidfies, and extreme events like marine heatwaves occur more frequently, outdoor livelihoods will experience steeper challenges.
Alaska prioritizes food security, and its residents receive the third-highest rate of Supplemental Nutrition Assistance Program benefits in the U.S. As COVID-19 highlighted, its supply chains are fragile. However, subsistence activities help to keep communities fed. But as changing sea ice, temperatures, and acid conditions shift populations of important food sources, as well as the behaviors of hunted land species, those carrying out subsistence activities experience new challenges.
The longer growing season with more growing degree days may help improve the availability of farmed food in Alaska. However, permafrost thaw, pests, and flooding will make those activities challenging, as well.
Needed adaptation will include monitoring and responding to changes in timing in fisheries and land-based resources, finding alternatives to hunting that depends on sea ice, and assessing and responding to increasingly volatile berry harvests. Many of these activities have long cultural traditions.
Alaskans are responding with climate planning efforts. Many Tribes are engaged in adaptation planning and implementation. The community pooling of subsistence resources and focus on well-being and cultural continuity undergird many of these adaptation efforts. However, ongoing effects of colonization, including difficult relationships between Tribal, state, and federal governments, make some adaptation work more difficult.
Nonetheless, growing interest in building out Alaskan solutions includes more community-supported agriculture, shared gardens, and supply boxes to supplement neighborhoods far from urban grocery stores. Examples like the Native Village of Port Heiden and the Knik Tribe are building out solutions like local farms, fish processing facilities, and new ways to feed local livestock.
As with the Caribbean islands, data collection on this area of the U.S. has long been lacking. The lack of data contributes to ongoing challenges with understanding and adapting to climate change in the region.
However, some substantial challenges are clear. Fisheries are declining because of coral bleaching, acidification, sea level rise, terrestrial sediment, and contaminants. The same factors shape the redistribution of fish stocks. Separately, warmer night temperatures, saltwater intrusion, drought, and increasing pathogens reduce the productivity of local agriculture.
However, restoration of Indigenous agroecological practices and improvement of planting stock are increasingly being identified as solutions to challenging weather conditions. Community networks of food-sharing, as well as efforts to strengthen natural resource management practices using traditional and customary skills, are providing sources of resilience.
Work is underway to change Hawai’ian law to allow for “Traditional Lands” zones to permit ecovillage-style living as well as food-system infrastructure like commercial kitchens and food processing. These could be accompanied, within the zoning, by the production of traditional staple crops and livestock like taro and fishponds.
Equitable outcomes for all of the needed changes will need continued focus on improving data collection and availability, including ensuring Indigenous sovereignty over decisions around Indigenous knowledge and intellectual property rights.
The climate challenges that U.S. agriculture faces are steep and are expected to continue to rise if emissions continue on their current trajectory. However, communities around the country are recognizing their own role in reducing emissions and adapting to changes. As recognition of the value of Indigenous, Tribal, and other traditional knowledge systems improves, and as respect for data and decision sovereignty of those groups increases, new solutions may continue to emerge into the larger consciousness that may help with many of the challenges of agriculture.
Adaptation and community co-production of knowledge are important and must be valued. Such work will provide improved food security and livelihood stability in the future. However, the most important change will continue to be the reduction of greenhouse gas emissions. Agriculture, along with dozens of other forms of work, must continue to push hard to reduce its nitrous oxide, methane, and carbon dioxide emissions through equitable means that provide the best possible ecosystem and community outcomes across the country.