This document summarizes the key effects of climate change on U.S. agriculture as identified in the report. It finds that rising temperatures and changing precipitation patterns will reduce productivity for most crops, outweighing benefits from increased carbon dioxide. Effects will vary by crop and region but all production systems will be impacted. Livestock are vulnerable to temperature stresses. Climate change will exacerbate existing biotic stresses from weeds, pests and diseases. It will also compromise ecosystem services like soil quality and water resources that support agriculture. The report calls for more research on extreme weather effects and improving agricultural adaptation through new crop varieties, practices and policies.

2. Climate Change and Agriculture
in the United States:
Effects and Adaptation
USDA Technical Bulletin 1935

3. Climate Change and Agriculture in the United States: Effects and Adaptation
Table of Contents
Executive Summary........................................................................................................................................................................................ 1
Key Messages.................................................................................................................................................................................................... 1
Introduction....................................................................................................................................................................................................... 2
Crop Response to Changing Climate..................................................................................................................................................... 3
Livestock Response to Changing Climate........................................................................................................................................... 4
Effects of Climate Change on Soil and Water..................................................................................................................................... 4
Extreme Events................................................................................................................................................................................................. 5
Adaptation......................................................................................................................................................................................................... 6
Research Needs................................................................................................................................................................................................ 7
Climate Change and Agriculture in the United States: Effects and Adaptation Understanding Exposure...................................................................................................................................................................... 7
Understanding Sensitivity.................................................................................................................................................................... 8
This document may be cited as:
Enhancing Adaptive Capacity............................................................................................................................................................. 8
Walthall, C.L., J. Hatfield, P. Backlund, L. Lengnick, E. Marshall, M. Walsh, S. Adkins, M. Aillery, E.A. Ainsworth,
C. Ammann, C.J. Anderson, I. Bartomeus, L.H. Baumgard, F. Booker, B. Bradley, D.M. Blumenthal, J. Bunce, K. Burkey,
S.M. Dabney, J.A. Delgado, J. Dukes, A. Funk, K. Garrett, M. Glenn, D.A. Grantz, D. Goodrich, S. Hu, R.C. Izaurralde, Chapter 1: U.S. Agriculture and Climate.................................................................................................................................... 9
R.A.C. Jones, S-H. Kim, A.D.B. Leaky, K. Lewers, T.L. Mader, A. McClung, J. Morgan, D.J. Muth, M. Nearing, D.M. Report Goals and Scope............................................................................................................................................................................... 9
O
­ osterhuis, D. Ort, C. Parmesan, W.T. Pettigrew, W. Polley, R. Rader, C. Rice, M. Rivington, E. Rosskopf, W.A. Salas, Document Organization............................................................................................................................................................................10
L.E. Sollenberger, R. Srygley, C. Stöckle, E.S. Takle, D. Timlin, J.W. White, R. Winfree, L. Wright-Morton, L.H. Ziska.
2012. Climate Change and Agriculture in the United States: Effects and Adaptation. USDA Technical Bulletin 1935. Authors...............................................................................................................................................................................................................10
Washington, DC. 186 pages.
Chapter 2: An Overview of U.S. Agriculture.........................................................................................................................11
Forces Affecting U.S. Agriculture...........................................................................................................................................................12
Economic Factors and U.S. Agriculture..........................................................................................................................................12
Effects of Technology on U.S. Agriculture.....................................................................................................................................17
Climate Effects on U.S. Agriculture..................................................................................................................................................17
This document was produced as part of of a collaboration between the U.S. Department of Agriculture, the University Agriculture: A Complex Social-Ecological System (SES).............................................................................................................19
Corporation for Atmospheric Research, and the National Center for Atmospheric Research under USDA cooperative New Research for a Novel Challenge..............................................................................................................................................20
agreement 58-0111-6-005. NCAR’s primary sponsor is the National Science Foundation.
Chapter 3: An Overview of the Changing Climate..........................................................................................................23
Images courtesy of USDA and UCAR. Evidence of Changing Climate Across the Globe...........................................................................................................................23
This report is available on the Web at: http://www.usda.gov/oce/climate_change/effects.htm Projections of Future Global Climate..................................................................................................................................................24
Changing Climate Across the United States: The Last 100 Years...........................................................................................24
Printed copies may be purchased from the National Technical Information Service. Call 1-800- 553-NTIS (6847) or Temperature............................................................................................................................................................................................26
703-605-6000, or visit http://www.ntis.gov.
Precipitation.............................................................................................................................................................................................27
November 2012 Projections of Future U.S. Climate Change.......................................................................................................................................29
Temperature............................................................................................................................................................................................29
Precipitation.............................................................................................................................................................................................30
The U.S. Department of Agriculture (USDA) prohibits discrimination in all of its programs and activities on the basis of race, color,
national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, Extreme Conditions...............................................................................................................................................................................31
political beliefs, genetic information, reprisal, or because all or part of an individual’s income is derived from any public assistance Changes in Tropospheric Ozone......................................................................................................................................................32
program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication
of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). Conclusions......................................................................................................................................................................................................33
To file a complaint of discrimination, write to USDA, Assistant Secretary for Civil Rights, Office of the Assistant Secretary for Civil Rights,
1400 Independence Avenue, S.W., Stop 9410, Washington, DC 20250-9410, or call toll-free at (866) 632-9992 (English) or (800) 877-
8339 (TDD) or (866) 377-8642 (English Federal-relay) or (800) 845-6136 (Spanish Federal-relay). USDA is an equal opportunity provider
and employer.
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4. Table of Contents Climate Change and Agriculture in the United States: Effects and Adaptation Climate Change and Agriculture in the United States: Effects and Adaptation Table of Contents
Chapter 4: Climate Change Science and Agriculture...................................................................................................35 Chapter 6: Climate Change Effects on the Economics of U.S. Agriculture................................................99
Direct Climate Change Effects.................................................................................................................................................................35 Economic Impacts and Agricultural Adaptation......................................................................................................................... 100
Air Temperature......................................................................................................................................................................................35 Estimating Economic Impacts of Climate Change...................................................................................................................... 101
Water..........................................................................................................................................................................................................36 Sensitivity of Economic Impact Estimates to Climate and Yield Projections................................................................ 103
Atmospheric Carbon Dioxide............................................................................................................................................................36 Sensitivity of Economic Impact Estimates to Scope of Analysis......................................................................................... 104
Tropospheric Ozone..............................................................................................................................................................................38 Sensitivity of Economic Impact Estimates to Socioeconomic and Technology Projections and
Indirect Climate Change Effects.............................................................................................................................................................39 Treatment of Adaptation Constraints.............................................................................................................................................. 106
Weeds and Invasive Plant Species...................................................................................................................................................39 The Changing Geography of Production................................................................................................................................... 107
Invasive Weeds........................................................................................................................................................................................41 Sensitivity of Economic Impact Estimates to Estimation Methodology......................................................................... 107
Insect Pests...............................................................................................................................................................................................44 International Effects and Food Security Implications.............................................................................................................. 108
Pathogens.................................................................................................................................................................................................49 Climate Change Effects and the Environment............................................................................................................................. 110
Conclusions......................................................................................................................................................................................................52 Climate Change, Economic Resilience, and Extreme Weather Events.............................................................................. 110
Extreme Events............................................................................................................................................................................................ 111
Chapter 5: Climate Change Effects on U.S. Agricultural Production.............................................................53 Crop Insurance..................................................................................................................................................................................... 112
Aggregate Effects..........................................................................................................................................................................................53 Workable Field Days........................................................................................................................................................................... 115
Agricultural Soil Resources.................................................................................................................................................................53 Soil Erosion............................................................................................................................................................................................ 116
Soil Degradation and Soil Erosion...................................................................................................................................................53 Conclusions................................................................................................................................................................................................... 118
Rainfall.......................................................................................................................................................................................................54
Irrigation....................................................................................................................................................................................................54 Chapter 7: Adapting to Climate Change............................................................................................................................... 119
Snow and Winter Processes................................................................................................................................................................55 Understanding Agricultural Vulnerability..................................................................................................................................... 119
Wind............................................................................................................................................................................................................55 Adaptation Drivers.................................................................................................................................................................................... 120
Changing Agricultural Production and the Effects on Soil Erosion.....................................................................................55 A Typology of Adaptation...................................................................................................................................................................... 121
Enhanced Atmospheric Carbon Dioxide.......................................................................................................................................56 Enhancing the Adaptive Capacity of Agriculture....................................................................................................................... 123
Adaptation................................................................................................................................................................................................56 Climate Policy....................................................................................................................................................................................... 124
Agricultural Water Resources and Irrigation...................................................................................................................................56 National Climate Change Adaptation Strategies.................................................................................................................... 125
The U.S. Irrigated Sector Under a Changing Climate................................................................................................................57 Agricultural Adaptation Policy....................................................................................................................................................... 125
Agricultural Water Requirements.....................................................................................................................................................57 Mitigation and Adaptation: Complement or Tradeoff?......................................................................................................... 126
Water-Supply Availability....................................................................................................................................................................57 Integrated Assessment of Mitigation and Adaptation Responses.................................................................................... 127
Returns to Crop Production...............................................................................................................................................................58 Adaptation Costs and Benefits....................................................................................................................................................... 128
Adaptation................................................................................................................................................................................................59 Limits to Adaptation................................................................................................................................................................................. 128
Ecosystem Services.......................................................................................................................................................................................59 Ecological Limits to Adaptation..................................................................................................................................................... 128
Pollinators.................................................................................................................................................................................................60 Social Barriers to Adaptation.......................................................................................................................................................... 129
Adaptation................................................................................................................................................................................................61 Assessing Options, Taking Action...................................................................................................................................................... 130
U.S. Agricultural Production....................................................................................................................................................................61 Vulnerability Assessment................................................................................................................................................................. 130
Corn and Soybean.................................................................................................................................................................................61 Assessing Adaptive Capacity.......................................................................................................................................................... 132
Rice..............................................................................................................................................................................................................63 Incremental Adaptation: Extending Existing Production Practices.................................................................................. 134
Wheat.........................................................................................................................................................................................................67 Managing Climate Risk: New Strategies for Novel Uncertainty......................................................................................... 136
Cotton........................................................................................................................................................................................................69 Conclusions................................................................................................................................................................................................... 137
Annual Specialty Crops........................................................................................................................................................................75 Risk Assessment and Climate Change: An overview.............................................................................................................. 137
Perennial Specialty Crops...................................................................................................................................................................78
Grazing Lands and Domestic Livestock.........................................................................................................................................88
Conclusions......................................................................................................................................................................................................97
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5. Table of Contents Climate Change and Agriculture in the United States: Effects and Adaptation
Chapter 8: Conclusions and Research Needs.................................................................................................................... 139 Climate Change and Agriculture in the United States:
Exposure to Changing Climate Conditions.................................................................................................................................... 140 Effects and Adaptation
Sensitivity to Changing Climate Conditions................................................................................................................................. 140
Capacity of the Agricultural System to Adapt to Changing Climate Conditions......................................................... 142 Executive Summary
Research Needs........................................................................................................................................................................................... 143
Understanding Exposure................................................................................................................................................................. 144
Understanding Sensitivity............................................................................................................................................................... 144
Enhancing Adaptive Capacity........................................................................................................................................................ 145 Key Messages
Understanding Basic Processes..................................................................................................................................................... 145
Climate Change and Sustainable Agriculture.............................................................................................................................. 146 Increases of atmospheric carbon dioxide (CO2),
rising temperatures, and altered precipitation
Appendix A: References Cited (by Chapter)...................................................................................................................... 147 patterns will affect agricultural productivity.
Increases in temperature coupled with more variable
Chapter 1 References......................................................................................................................................................................... 147
precipitation will reduce productivity of crops, and
Chapter 2 References......................................................................................................................................................................... 147 these effects will outweigh the benefits of increasing
Chapter 3 References......................................................................................................................................................................... 148 carbon dioxide. Effects will vary among annual and
Chapter 4 References......................................................................................................................................................................... 149 perennial crops, and regions of the United States;
however, all production systems will be affected to
Chapter 5 References......................................................................................................................................................................... 155
some degree by climate change. Agricultural systems
Chapter 6 References......................................................................................................................................................................... 172 depend upon reliable water sources, and the pattern
Chapter 7 References......................................................................................................................................................................... 174 and potential magnitude of precipitation changes is
Chapter 8 References......................................................................................................................................................................... 179 not well understood, thus adding considerable uncer-
Fig. 1. Storm gathers over farmland. Image courtesy UCAR.
tainty to assessment efforts.
Appendix B: Glossary of Commonly Used Terms.......................................................................................................... 181
Livestock production systems are vulnerable to physiological and genetic responses may help guide
temperature stresses. An animal’s ability to adjust future enhancements to weed management.
Appendix C: Report Authors and Affiliations................................................................................................................... 184
its metabolic rate to cope with temperature extremes
can lead to reduced productivity and in extreme cases Agriculture is dependent on a wide range of eco-
death. Prolonged exposure to extreme temperatures system processes that support productivity includ-
will also further increase production costs and pro- ing maintenance of soil quality and regulation
ductivity losses associated with all animal products, of water quality and quantity. Multiple stressors,
e.g., meat, eggs, and milk. including climate change, increasingly compromise
the ability of ecosystems to provide these services.
Projections for crops and livestock production Key near-term climate change effects on agricultural
systems reveal that climate change effects over the soil and water resources include the potential for
next 25 years will be mixed. The continued degree increased soil erosion through extreme precipitation
of change in the climate by midcentury and beyond is events, as well as regional and seasonal changes in
expected to have overall detrimental effects on most the availability of water resources for both rain-fed
crops and livestock. and irrigated agriculture.
Climate change will exacerbate current biotic The predicted higher incidence of extreme
stresses on agricultural plants and animals. weather events will have an increasing influence
Changing pressures associated with weeds, diseases, on agricultural productivity. Extremes matter
and insect pests, together with potential changes in because agricultural productivity is driven largely by
timing and coincidence of pollinator lifecycles, will environmental conditions during critical threshold
affect growth and yields. The potential magnitude of periods of crop and livestock development. Improved
these effects is not yet well understood. For example, assessment of climate change effects on agricultural
while some pest insects will thrive under increas- productivity requires greater integration of extreme
ing air temperatures, warming temperatures may events into crop and economic models.
force others out of their current geographical ranges.
S
­ everal weeds have shown a greater response to The vulnerability of agriculture to climatic change
carbon dioxide relative to crops; understanding these is strongly dependent on the responses taken by
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6. Executive Summary Climate Change and Agriculture in the United States: Effects and Adaptation Climate Change and Agriculture in the United States: Effects and Adaptation Executive Summary
humans to moderate the effects of climate change. Introduction incorporate production constraints caused by changes While many agricultural enterprises have the option
Adaptive actions within agricultural sectors are driven of pest pressures, ecosystem services and conditions to respond to climate changes by shifting crop
by perceptions of risk, direct productivity effects of Agriculture in the United States produces that limit adaptation that can significantly increase selection, development of new cultivars in perennial
climate change, and by complex changes in domes- approximately $300 billion a year in commodities production costs and yield losses. specialty crops commonly requires 15 to 30 or more
tic and international markets, policies, and other with livestock accounting for roughly half the value. years, greatly limiting that sector’s opportunity to
institutions as they respond to those effects within Production of these commodities is vulnerable to adapt by shifting cultivars unless cultivars can be
the United States and worldwide. Opportunities for climate change through the direct (i.e., abiotic) Crop Response to Changing Climate introduced from other areas.
adaptation are shaped by the operating context within effects of changing climate conditions on crop and
which decision‑making occurs, access to effective livestock development and yield (e.g., changes in Plant response to climate change is dictated by a An increase in winter temperatures also affects
adaptation options, and the capacity of individuals temperature or precipitation), as well as through the complex set of interactions to CO2, temperature, perennial cropping systems through interactions
and institutions to take adaptive action as climate con- indirect (i.e., biotic) effects arising from changes solar radiation, and precipitation. Each crop species with plant chilling requirements. All perennial
ditions change. Effective adaptive action across the in the severity of pest pressures, availability has a given set of temperature thresholds that define specialty crops have a winter chilling requirement
multiple dimensions of the U.S. agricultural system of pollination services, and performance of the upper and lower boundaries for growth and (typically expressed as hours below 10°C and above
offers potential to capitalize on emerging opportuni- other ecosystem services that affect agricultural reproduction, along with optimum temperatures 0°C) ranging from 200 to 2,000 cumulative hours.
ties and minimize the costs associated with climate productivity. Thus, U.S. agriculture exists as a for each developmental phase. Plants are currently Yields will decline if the chilling requirement is
change. A climate-ready U.S. agriculture will depend complex web of interactions between agricultural grown in areas in which they are exposed to not completely satisfied because flower emergence
on the development of geographically specific, agri- productivity, ecosystem services, and climate change. temperatures that match their threshold values. and viability will be low. Projected air temperature
culturally relevant, climate projections for the near As temperatures increase over the next century, increases for California, for example, may prevent
and medium term; effective adaptation planning and Climate change poses unprecedented challenges shifts may occur in crop production areas because the chilling requirements for fruit and nut trees by
assessment strategies; and soil, crop and livestock to U.S. agriculture because of the sensitivity of temperatures will no longer occur within the range, the middle to the end of the 21st century. In the
management practices that enhance agricultural pro- agricultural productivity and costs to changing or during the critical time period for optimal growth Northeast United States, perennial crops with a
duction system resilience to climatic variability and climate conditions. Adaptive action offers the and yield of grain or fruit. lower 400-hour chilling requirement will continue
extremes. Anticipated adaptation to climate change potential to manage the effects of climate change by to be met for most of the Northeast during this
in production agriculture includes adjustments to altering patterns of agricultural activity to capitalize For example, one critical period of exposure to century, but crops with prolonged cold requirements
production system inputs, tillage, crop species, crop on emerging opportunities while minimizing the temperatures is the pollination stage, when pollen is (1,000 or more hours) could demonstrate reduced
Climate change rotations, and harvest strategies. New research and costs associated with negative effects. The aggregate released to fertilize the plant and trigger development yields, particularly in southern sections of the
poses unprecedented development in new crop varieties that are more resis- effects of climate change will ultimately depend on a of reproductive organs, for fruit, grain, or fiber. Such Northeast. Climate change affects winter temperature
challenges to U.S. tant to drought, disease, and heat stress will increase complex web of adaptive responses to local climate thresholds are typically cooler for each crop than variability, as well; mid-winter warming can lead
agriculture because of the the resilience of agronomic systems to climate change stressors. These adaptive responses may range the thresholds and optima for growth. Pollination to early bud-burst or bloom of some perennial
sensitivity of agricultural and will enable exploitation of opportunities that may from farmers adjusting planting patterns and soil is one of the most sensitive stages to temperatures, plants, resulting in frost damage when cold winter
productivity and costs arise. management practices in response to more variable and exposure to high temperatures during this period temperatures return.
to changing climate weather patterns, to seed producers investing in can greatly reduce crop yields and increase the
conditions. Over the last 150 years, U.S. agriculture has the development of drought-tolerant varieties, to risk of total crop failure. Plants exposed to warm Increasing carbon dioxide (CO2) in the atmosphere
exhibited a remarkable capacity to adapt to a wide increased demand for Federal risk management nighttime temperatures during grain, fiber, or fruit is a positive for plant growth, and controlled
diversity of growing conditions amid dynamic programs, to adjustments in international trade as production also experience lower productivity and experiments have documented that elevated CO2
social and economic changes. These adaptations nations respond to food security concerns. Potential reduced quality. Increasing temperatures cause concentrations can increase plant growth while
were made during a period of relative climatic stabil- adaptive behavior can occur at multiple levels in plants to mature and complete their stages of decreasing soil water-use rates. The effects of
ity and abundant technical, financial and natural a highly diverse international agricultural system development faster, which may alter the feasibility elevated CO2 on grain and fruit yield and quality,
resources. Future agricultural adaptation will be including production, consumption, education, and profitability of regional crop rotations and field however, are mixed; reduced nitrogen and protein
undertaken in a decision environment characterized research, services, and governance. Understanding management options, including double-cropping and content observed in some nitrogen-fixing plants
by high complexity and uncertainty driven by the the complexity of such interactions is critical for use of cover crops. Faster growth may create smaller causes a reduction in grain and forage quality. This
sensitivity of agricultural system response to climatic developing effective adaptive strategies. plants, because soil may not be able to supply water effect reduces the ability of pasture and rangeland
variability, the complexity of interactions between or nutrients at required rates, thereby reducing to support grazing livestock. The magnitude of
the agricultural systems, non-climate stressors and The U.S. agricultural system is expected to be grain, forage, fruit, or fiber production. Increasing the growth stimulation effect of elevated CO2
the global climate system, and the increasing pace fairly resilient to climate change in the short term temperatures also increase the rate of water use concentrations under field conditions, in conjunction
and intensity of climatic change. New approaches due to the system’s flexibility to engage in adaptive by plants, causing more water stress in areas with with changing water and nutrient constraints, is
to managing the uncertainty associated with climate behaviors such as expansion of irrigated acreage, variable precipitation. Estimated reductions in solar uncertain. Because elevated CO2 concentrations
change, such as integrated assessment of climate regional shifts in acreage for specific crops, crop radiation in agricultural areas over the last 60 years disproportionately stimulate growth of weed species,
change effects and adaptation options, the use of rotations, changes to management decisions such as are projected to continue due to increased cloud they are likely to contribute to increased risk of crop
adaptive management and robust decision-support choice and timing of inputs and cultivation practices, cover and radiative scattering caused by atmospheric loss from weed pressure.
strategies, the integration of climate knowledge into and altered trade patterns compensating for yield aerosols. Such reductions may partially offset the
decisionmaking by producers, technical advisors, changes caused by changing climate patterns. By temperature-induced acceleration of plant growth. The effects of elevated CO2 on water-use efficiency
and agricultural research and development planning midcentury, when temperature increases are expected For vegetables, exposure to temperatures in the may be an advantage for areas with limited
efforts, and the development of resilient agricultural to exceed 1°C to 3°C and precipitation extremes range of 1°C to 4°C above optimal for biomass precipitation. Other changing climate conditions may
production systems will help to sustain agricultural intensify, yields of major U.S. crops and farm returns growth moderately reduces yield, and exposure to either offset or complement such effects. Warming
production during the 21st century. are projected to decline. However, the simulation temperatures more than 5°C to 7°C above optimal temperatures, for instance, will act to increase crop
studies underlying such projections often fail to often leads to severe, if not total, production losses. water demand, increasing the rate of water use by
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7. Executive Summary Climate Change and Agriculture in the United States: Effects and Adaptation Climate Change and Agriculture in the United States: Effects and Adaptation Executive Summary
crops. Crops grown on soils with a limiting soil Livestock production systems that provide partial acidification, salinization, toxification, and net loss of Climate change effects on snowpack have important
water-holding capacity are likely to experience an or total shelter to mitigate thermal environmental organic matter. implications for surface-water availability and stored
increased risk of drought and potential crop failure challenges can reduce the risk and vulnerability water reserves, particularly in the West, where much
as a result of temperature-induced increases in associated with adverse weather events. Livestock Several of these processes are sensitive to changing of the surface-water runoff comes from mountain
crop water demand, even with improved water-use such as poultry and swine are generally managed climate conditions. Changes to the rate of soil snowmelt. Higher temperatures will continue to
efficiencies. Conversely, declining trends of near- in housed systems where airflow can be controlled organic matter accumulation will be affected restrict the snow storage season, resulting in reduced
surface winds over the last several decades and and housing temperature modified to minimize or by climate through soil temperature, soil water snow accumulations and earlier spring snowmelt.
projections for future declines of winds may decrease buffer against adverse environmental conditions. availability, and the amount of organic matter Stored water reserves are projected to decline in
evapotranspiration of cropping regions. However, management and energy costs associated input from plants. Erosion is of particular concern. many river basins, especially during critical summer
Climate affects
with increased temperature regulation will increase Changing climate will contribute to the erosivity growing season months when crop-water demands
microbial populations
Crops and forage plants will continue to be subjected for confined production enterprises. Protection of from rainfall, snowmelt, and wind. Rainfall’s erosive are greatest. As a result, agriculture may become
and distribution, the
to increasing temperatures, increasing CO2, and animals against exposure to high temperatures will power will increase if increases in rainfall amount increasingly water constrained across the central
distribution of vector-
more variable water availability caused by changing require modification of shelter and perhaps even are accompanied by increases of intensity. Shifts and southern portions of the Mountain and Pacific
borne diseases, host
precipitation patterns. These factors interact in methods of increasing cooling. of rainfall intensity have begun to occur in the Southwest regions, while projected precipitation
resistance to infections,
their effect on plant growth and yield. A balanced United States with more extreme events expected increases in the Northern Rockies and Pacific Changes in production
food and water shortages,
understanding of the consequences of management Warmer, more humid conditions will also have for the future. Although there is a general lack of Northwest could improve surface-water supplies for practices can also have
and food-borne diseases.
actions and genetic responses to these factors will indirect effects on animal health and productivity knowledge about the rates of soil erosion associated those areas. effects on soil erosion
form the basis for more resilient production systems through promotion of insect growth and spread with snowmelt or rain-on-thawing-soil erosion, if that may be greater than
to climate change. Due to the complexities of these of diseases. Such effects may be substantial; decreased days of snowfall translate to increased The effect of precipitation changes on surface-water other effects of climate
relationships, integrated research and development however, exact relationships between climate days of rainfall, erosion by storm runoff is likely to flows may be offset or compounded by temperature- change. Tillage intensity,
of management practices, plant genetics, change and vectors of animal health are not well increase. induced shifts of potential evapotranspiration. crop selection, as well
hydrometeorology, socio-economics, and agronomy understood. Climate affects microbial populations Higher temperatures are projected to increase both as planting and harvest
is necessary to enable successful agricultural and distribution, the distribution of vector-borne Changes in production practices can also have effects evaporative losses from land and water surfaces, dates can significantly
adaptation to climate change. diseases, host resistance to infections, food and on soil erosion that may be greater than other effects and transpiration losses from non-crop land cover, affect runoff and soil loss.
water shortages, and food-borne diseases. Earlier of climate change. Tillage intensity, crop selection, potentially reducing annual runoff and streamflow.
springs and warmer winters may enable greater as well as planting and harvest dates can significantly The resulting shifts of water stress, crop yields, and
Livestock Response to Changing proliferation and survivability of pathogens and affect runoff and soil loss. Though the magnitude of crop competitiveness, in turn, will drive changes of
Climate parasites. Regional warming and changes of rainfall these effects is still highly uncertain, studies have cropland allocations and production systems within
distribution may lead to changes in the spatial shown potential for significant increases of erosion and across regions.
Animal agriculture is a major component of the U.S. or temporal distributions of diseases sensitive to loss, in part due to a reduction of projected crop
agricultural system. Changing climatic conditions temperature and moisture, such as anthrax, blackleg, biomass, which results in less overwintering residue Groundwater is a primary water source for irrigation
affect animal agriculture in four primary ways: (1) hemorrhagic septicemia, as well as increased available to protect the soil. As soil erosion changes in the Plains States and an important irrigation water
feed-grain production, availability and price; (2) incidence of ketosis, mastitis and lameness in dairy under climate change, so does the potential for supply for the Eastern United States, as well as areas
pastures and forage crop production and quality; cows. associated, off-site, non-point-source pollution. Soil of the Mountain and Pacific West regions. While
(3) animal health, growth and reproduction; and conservation practices will therefore be an important groundwater aquifers are generally less influenced in
(4) disease and pest distributions. The optimal element of agricultural adaptation to climate change. the short term by weather patterns, changing climate
environmental conditions for livestock production Effects of Climate Change on Soil and effects on precipitation, streamflow, and soil water
include a range of temperatures and other Water Changing climate conditions over the coming evaporation can affect groundwater systems over
environmental conditions for which the animal decades will also significantly affect water resources, time through changes in groundwater recharge.
does not need to significantly alter behavior or Climate change effects on agriculture also include the with broad implications for the U.S. crop sector.
physiological functions to maintain a relatively effects of changing climate conditions on resources Climate change will affect surface-water resources,
constant core body temperature. Optimum animal of key importance to agricultural production, such which account for 58% of water withdrawals for Extreme Events
core body temperature is often maintained within a as soil and water. Seasonal precipitation affects irrigated production nationally. Rising temperatures
2°C to 3°C range. For many species, deviations of the potential amount of water available for crop and shifting precipitation patterns will alter crop- Climate change projections into the future suggest
core body temperature in excess of 2°C to 3°C cause production, but the actual amount of water available water requirements, crop-water availability, crop an increased variability of temperature and
disruptions of performance, production, and fertility to plants also depends upon soil type, soil water- productivity, and costs of water access across the precipitation. Extreme climate conditions, such
that limit an animal’s ability to produce meat, milk, holding capacity, and infiltration rate. Healthy soils agricultural landscape. Temperature and precipitation as dry spells, sustained drought, and heat waves
or eggs. Deviations of 5°C to 7°C often result have characteristics that include appropriate levels shifts are expected to alter the volume and timing of can have large effects on crops and livestock.
in death. For cattle that breed during spring and of nutrients necessary for the production of healthy storm and snowmelt runoff to surface water bodies. Although climate models are limited in their ability
summer, exposure to high temperatures decreases plants, moderately high levels of organic matter, a Annual streamflow may increase in the northern and to accurately project the occurrence and timing
conception rates. Livestock and dairy production soil structure with good aggregation of the primary eastern United States, where annual precipitation of individual extreme events, emerging patterns
may be more affected by changes in the number of soil particles and macro-porosity, moderate pH is projected to increase. Precipitation declines for project increased incidence of areas experiencing
days of extreme heat than by adjustments of average levels, thickness sufficient to store adequate water for regions such as the Southwest and Southern Plains droughts and periods of more intense precipitation.
temperature. The combined effect of temperature and plants, a healthy microbial community, and absence will result in reduced streamflow and a shift of The occurrence of very hot nights and the duration
humidity affect animal response and are quantified of elements or compounds in concentrations toxic for seasonal flow volumes to the wetter winter months in of very low (agriculturally insignificant) rainfall
through the thermal-humidity index. plant, animal, and microbial life. Several processes areas already dominated by irrigation. events are projected to increase by the end of the
act to degrade soils including, erosion, compaction, 21st century. The timing of extreme events relative to
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8. Executive Summary Climate Change and Agriculture in the United States: Effects and Adaptation Climate Change and Agriculture in the United States: Effects and Adaptation Executive Summary
sensitive phenological stages could affect growth and Vulnerability and adaptive capacity are characteris- National agricultural adaptation planning has only capacity of U.S. agriculture to climate change.
productivity. tics of human and natural systems, are dynamic and recently begun in the United States and elsewhere. Attention to these research needs will enhance the
multi-dimensional, and are influenced by complex Broad policy measures that may enhance the adap- ability of the U.S. agriculture sector to anticipate
Crops and livestock production will be affected by interactions among social, economic, and environ- tive capacity of agriculture include strengthening and respond to the challenges presented by changing
increased exposure to extreme temperature events mental factors. Adaptive decisions are shaped by climate-sensitive assets, integrating adaptation into climate conditions.
and increased risk of exceeding the maximum the operating context within which decision are all relevant government policies, and addressing
temperature thresholds, potentially leading to made (for example, existing natural resource quality non-climate stressors that degrade adaptive capacity. Some broad research needs include the following:
catastrophic losses. Ruminants, including, goats, and non-climate stressors, government policy and Because of the uncertainties associated with climate
sheep, beef cattle and dairy cattle tend to be managed programs), access to effective adaptation options, change effects on agriculture and the complexity of • Improve projections of future climate conditions
in more extensive outdoor facilities. Within limits, and the individual capability to take adaptive action. adaptation processes, adaptive management strate- for time scales of seasons to multiple decades;
these animals can adapt to and cope with gradual Adaptation strategies in use today by U.S. farmers gies that facilitate implementation and the continual enable more precise projections of the changes
thermal changes, though shifts in thermoregulation coping with current changes in weather variability evaluation and revision of adaptation strategies as and durations of average and extreme tempera-
may result in a loss of productivity. Lack of prior include changing cultivar selection or timing of field climate learning proceeds will be necessary to ensure tures, precipitation, and related variables (e.g.,
conditioning to rapidly changing or adverse weather operations, and increased use of pesticides to control agricultural systems remain viable with climate evapotranspiration, soil moisture).
events, however, often results in catastrophic deaths higher pest pressures. In California’s Central Valley, change. Synergies between mitigation and adaptation
of domestic livestock and losses of productivity by an adaptation plan consisting of integrated changes in planning are also possible through the use of coher- • Evaluate and develop process-level understanding
surviving animals. crop mix, irrigation methods, fertilization practices, ent climate policy frameworks that link issues such of the sensitivity of plant and animal production
tillage practices, and land management was found to as carbon sequestration, greenhouse gas emissions, systems, including insect, weed, pathogen, soil
be the most effective approach to managing climate land-use change, regional water management, and and water components, to key direct, indirect and
Adaptation risk. Adaptation options for managing novel crop the long-term sustainability of production systems. interacting effects of climate change effects.
pest management challenges may involve increased
U.S. agriculture has demonstrated a remarkable use of pesticides, new strategies for preventing rapid High adaptive capacity does not guarantee successful • Develop and extend the knowledge, management Adapting agricultural
adaptive capacity over the last 150 years. Crop and evolution of pest resistance to chemical control adaptation to climate change. Adaptation assessment strategies and tools needed by U.S. agricultural systems to dramatic
livestock production systems expanded across a agents, the development of new pesticide products and planning efforts routinely encounter conditions stakeholders to enhance the adaptive capacity of changes in the physical
diversity of growing conditions, responded to varia- and improved pest and disease forecasting. Adapta- that limit adaptive action regardless of the adap- plant and animal production systems to climate environment may be
tions in climate and other natural resources, and to tion options that increase the resilience of agricul- tive capacity of the system under study. Potential variability and extremes. While existing manage- limited by social factors
dynamic changes in agricultural knowledge, technol- tural systems to increased pest pressures include crop constraints to adaptation can arise from ecological, ment and agronomic options have demonstrated such as values, beliefs, or
ogy, markets, and, most recently, public demands for diversification and the management of biodiversity social and economic conditions that are dynamic significant capacity for expanding adaptation world views. Those factors
sustainable production of agricultural products. This at both field and landscape scale to suppress pest and vary greatly within and across economic sectors, opportunities, new adaptive management strate- can be affected by access
adaptive capacity has been driven largely by public outbreaks and pathogen transmission. Given the communities, regions, and countries. gies, robust risk management approaches, and to finance, political norms
sector investment in agricultural research, develop- projected effects of climate change, some U.S. agri- breeding and genetic advances offer much poten- and values, and culture
ment, and extension activities made during a period cultural systems will have to undergo more transfor- Adapting agricultural systems to dramatic changes tial, but have yet to be evaluated. and religious ideologies.
of climatic stability and abundant technical, financial, mative changes to remain productive and profitable. in the physical environment may be limited by
and natural resource availability. social factors such as values, beliefs, or world views. Understanding Exposure
Adaptation measures such as developing drought, Those factors can be affected by access to finance,
Climate change presents an unprecedented challenge pest, and heat stress resistance in crops and animals, political norms and values, and culture and religious The vulnerability of an agricultural system to climate
to the adaptive capacity of U.S. agriculture. Current diversifying crop rotations, integrating livestock with ideologies. change is dependent in part on the character, magni-
climate change effects are increasing the complex- crop production systems, improving soil quality, tude and rate of climate variation to which a system
ity and uncertainty of agricultural management. minimizing off-farm flow of nutrients and pesti- Other limits to adaptation include the availability of is exposed. Effective adaptation will be enhanced by
Projected climate changes over the next century may cides, and other practices typically associated with critical inputs such as land and water, and constraints research to:
require major adjustments to production practices, sustainable agriculture are actions that may increase to farm financing and credit availability. These con-
particularly for production systems operating at the capacity of the agricultural system to minimize straints may be substantial, especially for agricul- • Improve projections of future climate conditions
their marginal limits of climate. Because agricul- the effects of climate change on productivity. For tural enterprises with little available capital or those for time scales of seasons to multiple decades,
tural systems are human-dominated ecosystems, example, developing drought and heat stress resistant without the financial capacity to withstand increas- including more precise information about changes
the vulnerability of agriculture to climatic change is crops will improve the ability of farmers to cope with ing variability of production and returns, including of average and extreme temperatures, precipita-
strongly dependent not just on the biophysical effects increasing frequencies of temperature and precipita- catastrophic loss. Differential capacity for adaptation, tion, and related variables (e.g., evapotranspira-
of climate change, but also on the responses taken by tion variability. Similarly, production practices that together with the variable effects of climate change tion, soil moisture). Such projections are needed
humans to moderate those effects within the United enhance the ability of healthy soils to regulate water on yield, creates significant concerns about agricul- to better understand exposure to climate risks,
States and worldwide. Effective adaptive action resource dynamics at the farm and watershed scales tural productivity and food security. and support effective assessment, planning, and
undertaken by the multiple dimensions of the U.S. will be particularly critical for the maintenance of decisionmaking across the multiple dimensions of
agricultural system offers potential for capitalizing crop and livestock productivity under conditions of the U.S. agricultural system.
on the opportunities presented by climate change, variable and extreme weather events. Enhancing the Research Needs
and minimizing the costs via avoidance or reduction resilience of agriculture to climate change through • Enable projection of future climate conditions
of the severity of detrimental effects from changing adaptation strategies that promote the development The research needs identified in this report are cate- at finer temporal scales (hourly and daily versus
climate. of sustainable agriculture is a common multiple- gorized within a vulnerability framework and address weekly, monthly, or annual averages) and spatial
benefit recommendation for agricultural adaptation specific actions that would serve to improve under- scales (1-10 km, as opposed to 50-100 km). This
planning. standing of the exposure, sensitivity, and adaptive
­ finer-scale information would permit decision-
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