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Vulnerabilities in Agriculture and Forestry

Climate change poses unprecedented challenges to U.S. agriculture because of the sensitivity of agricultural productivity and costs to changing climate conditions. Agriculture in the United States produces approximately $300 billion a year in commodities. Production of these commodities is vulnerable to climate change through the direct effects of changing climate conditions, for example changes in temperature or precipitation, as well as through the indirect effects arising from changes in the severity of pest pressures, availability of pollination services, and performance of other ecosystem services that affect agricultural productivity. Thus, U.S. agriculture exists as a complex web of interactions between agricultural productivity, ecosystem services, and climate change.

Similarly, projected changes in climate, increased atmospheric carbon dioxide, and increased nitrogen deposition are likely to affect U.S. forests throughout this century. Effects will be both direct, for example by elevated carbon dioxide on forest growth and water use, and indirect, through altered disturbance regimes, and will differ temporally and spatially across the United States.

 

 

USDA: Modern Solutions for Environmental Challenges

 

A summary of climate change vulnerabilities in the agriculture and forestry sectors is below.

Agriculture 

Increases of atmospheric carbon dioxide (CO2), rising temperatures, and altered precipitation patterns will affect agricultural productivity. Increases in temperature coupled with more variable precipitation will reduce productivity of crops, and these effects will outweigh the benefits of increasing carbon dioxide. Effects will vary among annual and perennial crops, and regions of the United States; however, all production systems will be affected to some degree by climate change. Agricultural systems depend upon reliable water sources, and the pattern and potential magnitude of precipitation changes is not well understood, thus adding considerable uncertainty to assessment efforts.

Livestock production systems are vulnerable to temperature stresses. An animal’s ability to adjust its metabolic rate to cope with temperature extremes can lead to reduced productivity and in extreme cases death. Prolonged exposure to extreme temperatures will also further increase production costs and productivity losses associated with all animal products, e.g., meat, eggs, and milk.

Animal Agriculture in a Changing Climate has developed a video highlighting Climate Change Impacts on Animal Agriculture.

as well as a video on Life Cycle Assessment and Greenhouse Gas Emissions from Animal Agriculture

Projections for crops and livestock production systems reveal that climate change effects over the next 25 years will be mixed. The continued degree of change in the climate by midcentury and beyond is expected to have overall detrimental effects on most crops and livestock.

Climate change will exacerbate current biotic stresses on agricultural plants and animals. Changing pressures associated with weeds, diseases, and insect pests, together with potential changes in timing and coincidence of pollinator lifecycles, will affect growth and yields. The potential magnitude of these effects is not yet well understood. For example, while some pest insects will thrive under increasing air temperatures, warming temperatures may force others out of their current geographical ranges. Several weeds have shown a greater response to carbon dioxide relative to crops; understanding these physiological and genetic responses may help guide future enhancements to weed management.

Agriculture is dependent on a wide range of ecosystem processes that support productivity including maintenance of soil quality and regulation of water quality and quantity. Multiple stressors, including climate change, increasingly compromise the ability of ecosystems to provide these services. Key near-term climate change effects on agricultural soil and water resources include the potential for increased soil erosion through extreme precipitation events, as well as regional and seasonal changes in the availability of water resources for both rain-fed and irrigated agriculture.

The predicted higher incidence of extreme weather events will have an increasing influence on agricultural productivity. Extremes matter because agricultural productivity is driven largely by environmental conditions during critical threshold periods of crop and livestock development. Improved assessment of climate change effects on agricultural productivity requires greater integration of extreme events into crop and economic models.

The vulnerability of agriculture to climatic change is strongly dependent on the responses taken by humans to moderate the effects of climate change. Adaptive actions within agricultural sectors are driven by perceptions of risk, direct productivity effects of climate change, and by complex changes in domestic and international markets, policies, and other institutions as they respond to those effects within the United States and worldwide. Opportunities for adaptation are shaped by the operating context within which decision‑making occurs, access to effective adaptation options, and the capacity of individuals and institutions to take adaptive action as climate conditions change. Effective adaptive action across the multiple dimensions of the U.S. agricultural system offers potential to capitalize on emerging opportunities and minimize the costs associated with climate change. A climate-ready U.S. agriculture will depend on the development of geographically specific, agriculturally relevant, climate projections for the near and medium term; effective adaptation planning and assessment strategies; and soil, crop and livestock management practices that enhance agricultural production system resilience to climatic variability and extremes. Anticipated adaptation to climate change in production agriculture includes adjustments to production system inputs, tillage, crop species, crop rotations, and harvest strategies. New research and development in new crop varieties that are more resistant to drought, disease, and heat stress will increase the resilience of agronomic systems to climate change and will enable exploitation of opportunities that may arise.

Over the last 150 years, U.S. agriculture has exhibited a remarkable capacity to adapt to a wide diversity of growing conditions amid dynamic social and economic changes. These adaptations were made during a period of relative climatic stability and abundant technical, financial and natural resources. Future agricultural adaptation will be undertaken in a decision environment characterized by high complexity and uncertainty driven by the sensitivity of agricultural system response to climatic variability, the complexity of interactions between the agricultural systems, non-climate stressors and the global climate system, and the increasing pace and intensity of climatic change. New approaches to managing the uncertainty associated with climate change, such as integrated assessment of climate change effects and adaptation options, the use of adaptive management and robust decision-support strategies, the integration of climate knowledge into decision making by producers, technical advisors, and agricultural research and development planning efforts, and the development of resilient agricultural production systems will help to sustain agricultural production during the 21st century.

Forestry

A gradual increase in temperature will alter the growing environment of many tree species throughout the United States, reducing the growth of some species (especially in dry forests) and increasing the growth of others (especially in high-elevation forests). Mortality may increase in older forests stressed by low soil moisture, and regeneration may decrease for species affected by low soil moisture and competition with other species during the seedling stage.

Forest growth and afforestation in the United States currently account for a net gain in carbon (C) storage, offsetting approximately 13 percent of the Nation’s fossil fuel CO2 production. During the next few decades, Eastern forest ecosystems are expected to continue to sequester C through favorable response to elevated CO2 and higher temperature, although retention of C will depend on maintaining or increasing total forest area. Western forest ecosystems may begin to emit C if wildfire area and insect disturbance increase as expected.

Future changes in forest ecosystems will occur on both public and private lands and will challenge our ability to provide ecosystem services desired by society, especially as human populations continue to grow and demands for ecosystem services increase. Climate change effects in forests are likely to cause losses of ecosystem services in some areas (e.g., timber production, water supply, recreational skiing), but they may improve and expand ecosystem services in others (e.g., increased growth of high-elevation trees, longer duration of trail access in high-snow regions). Some areas may be particularly vulnerable because current infrastructure and resource production are based on past climate and the assumption of steady-state natural resource conditions. Any change in forest ecosystems that affects water resources will typically result in a significant loss of ecosystem services.

The most rapidly visible and significant short-term effects on forest ecosystems will be caused by altered disturbance regimes, often occurring with increased frequency and severity. Interacting disturbances will have the biggest effects on ecosystem responses, simultaneously altering species composition, structure, and function. The type and magnitude of disturbances will differ regionally and will pose significant challenges for resource managers to mitigate and reduce damage to resource values:

• Wildfire will increase throughout the United States, causing at least a doubling of area burned by the mid-21st century.

• Insect infestations, such as the current advance of bark beetles in forests throughout the Western United States and Canada, will expand, often affecting more land area per year than wildfire.

• Invasive species will likely become more widespread, especially in areas subject to increased disturbance and in dry forest ecosystems.

• Increased flooding, erosion, and movement of sediment into streams will be caused by (1) higher precipitation intensity in some regions (e.g., Southern United States), (2) higher rain:snow ratios in mountainous regions (western mountains), and (3) higher area burned (western dry forests). These increases will be highly variable in space and time, affecting decisions about management of roads and other infrastructure, as well as access for users of forest land.

• Increased drought will exacerbate stress complexes that include insects, fire, and invasive species, leading to higher tree mortality, slow regeneration in some species, and altered species assemblages.

 

 

Climate Change Vulnerabilities Across the U.S.

USDA’s Climate Hubs aim to better prepare farmers with adaptive responses to climate change by working with producers and landowners to deliver science-based, region-specific information and technologies to enable climate-smart decision making. Because the effects of climate change will vary by region, adaptation requires a regionally-targeted approach.

 

This page features information from USDA's 2013 reports, Climate Change and Agriculture in the United States: Effects and Adaptation, and Effects of Climatic Variability and Change on Forest Ecosystems: A Comprehensive Science Synthesis for the U.S. Forest Sector