TODAY’S STUDY: CLIMATE CHANGE ON THE FARM

Climate Change and Agriculture in the United States; Effects and Adaptation

Walthall, Hatfield, et. al., February 2013 (U.S. Department of Agriculture)

Executive Summary

Key Messages

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.

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.

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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.

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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.

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Introduction

Agriculture in the United States produces approximately $300 billion a year in commodities with livestock accounting for roughly half the value. Production of these commodities is vulnerable to climate change through the direct (i.e., abiotic) effects of changing climate conditions on crop and livestock development and yield (e.g., changes in temperature or precipitation), as well as through the indirect (i.e., biotic) 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.

Climate change poses unprecedented challenges to U.S. agriculture because of the sensitivity of agricultural productivity and costs to changing climate conditions. Adaptive action offers the potential to manage the effects of climate change by altering patterns of agricultural activity to capitalize on emerging opportunities while minimizing the costs associated with negative effects. The aggregate effects of climate change will ultimately depend on a complex web of adaptive responses to local climate stressors. These adaptive responses may range from farmers adjusting planting patterns and soil management practices in response to more variable weather patterns, to seed producers investing in the development of drought-tolerant varieties, to increased demand for Federal risk management programs, to adjustments in international trade as nations respond to food security concerns. Potential adaptive behavior can occur at multiple levels in a highly diverse international agricultural system including production, consumption, education, research, services, and governance. Understanding the complexity of such interactions is critical for developing effective adaptive strategies.

The U.S. agricultural system is expected to be fairly resilient to climate change in the short term due to the system’s flexibility to engage in adaptive behaviors such as expansion of irrigated acreage, regional shifts in acreage for specific crops, crop rotations, changes to management decisions such as choice and timing of inputs and cultivation practices, and altered trade patterns compensating for yield changes caused by changing climate patterns. By midcentury, when temperature increases are expected to exceed 1°C to 3°C and precipitation extremes intensify, yields of major U.S. crops and farm returns are projected to decline. However, the simulation studies underlying such projections often fail to incorporate production constraints caused by changes of pest pressures, ecosystem services and conditions that limit adaptation that can significantly increase production costs and yield losses…

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Extreme Events

Climate change projections into the future suggest an increased variability of temperature and precipitation. Extreme climate conditions, such as dry spells, sustained drought, and heat waves can have large effects on crops and livestock. Although climate models are limited in their ability to accurately project the occurrence and timing of individual extreme events, emerging patterns project increased incidence of areas experiencing droughts and periods of more intense precipitation. The occurrence of very hot nights and the duration of very low (agriculturally insignificant) rainfall events are projected to increase by the end of the 21st century. The timing of extreme events relative to sensitive phenological stages could affect growth and productivity.

Crops and livestock production will be affected by increased exposure to extreme temperature events and increased risk of exceeding the maximum temperature thresholds, potentially leading to catastrophic losses. Ruminants, including, goats, sheep, beef cattle and dairy cattle tend to be managed in more extensive outdoor facilities. Within limits, these animals can adapt to and cope with gradual thermal changes, though shifts in thermoregulation may result in a loss of productivity. Lack of prior conditioning to rapidly changing or adverse weather events, however, often results in catastrophic deaths of domestic livestock and losses of productivity by surviving animals.

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Adaptation

U.S. agriculture has demonstrated a remarkable adaptive capacity over the last 150 years. Crop and livestock production systems expanded across a diversity of growing conditions, responded to variations in climate and other natural resources, and to dynamic changes in agricultural knowledge, technology, markets, and, most recently, public demands for sustainable production of agricultural products. This adaptive capacity has been driven largely by public sector investment in agricultural research, development, and extension activities made during a period of climatic stability and abundant technical, financial, and natural resource availability.

Climate change presents an unprecedented challenge to the adaptive capacity of U.S. agriculture. Current climate change effects are increasing the complexity and uncertainty of agricultural management. Projected climate changes over the next century may require major adjustments to production practices, particularly for production systems operating at their marginal limits of climate. Because agricultural systems are human-dominated ecosystems, the vulnerability of agriculture to climatic change is strongly dependent not just on the biophysical effects of climate change, but also on the responses taken by humans to moderate those effects within the United States and worldwide. Effective adaptive action undertaken by the multiple dimensions of the U.S. agricultural system offers potential for capitalizing on the opportunities presented by climate change, and minimizing the costs via avoidance or reduction of the severity of detrimental effects from changing climate.

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Vulnerability and adaptive capacity are characteristics of human and natural systems, are dynamic and multi-dimensional, and are influenced by complex interactions among social, economic, and environmental factors. Adaptive decisions are shaped by the operating context within which decision are made (for example, existing natural resource quality and non-climate stressors, government policy and programs), access to effective adaptation options, and the individual capability to take adaptive action. Adaptation strategies in use today by U.S. farmers coping with current changes in weather variability include changing cultivar selection or timing of field operations, and increased use of pesticides to control higher pest pressures. In California’s Central Valley, an adaptation plan consisting of integrated changes in crop mix, irrigation methods, fertilization practices, tillage practices, and land management was found to be the most effective approach to managing climate risk. Adaptation options for managing novel crop pest management challenges may involve increased use of pesticides, new strategies for preventing rapid evolution of pest resistance to chemical control agents, the development of new pesticide products and improved pest and disease forecasting. Adaptation options that increase the resilience of agricultural systems to increased pest pressures include crop diversification and the management of biodiversity at both field and landscape scale to suppress pest outbreaks and pathogen transmission. Given the projected effects of climate change, some U.S. agricultural systems will have to undergo more transformative changes to remain productive and profitable.

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Adaptation measures such as developing drought, pest, and heat stress resistance in crops and animals, diversifying crop rotations, integrating livestock with crop production systems, improving soil quality, minimizing off-farm flow of nutrients and pesticides, and other practices typically associated with sustainable agriculture are actions that may increase the capacity of the agricultural system to minimize the effects of climate change on productivity. For example, developing drought and heat stress resistant crops will improve the ability of farmers to cope with increasing frequencies of temperature and precipitation variability. Similarly, production practices that enhance the ability of healthy soils to regulate water resource dynamics at the farm and watershed scales will be particularly critical for the maintenance of crop and livestock productivity under conditions of variable and extreme weather events. Enhancing the resilience of agriculture to climate change through adaptation strategies that promote the development of sustainable agriculture is a common multiplebenefit recommendation for agricultural adaptation planning.

National agricultural adaptation planning has only recently begun in the United States and elsewhere. Broad policy measures that may enhance the adaptive capacity of agriculture include strengthening climate-sensitive assets, integrating adaptation into all relevant government policies, and addressing non-climate stressors that degrade adaptive capacity. Because of the uncertainties associated with climate change effects on agriculture and the complexity of adaptation processes, adaptive management strategies that facilitate implementation and the continual evaluation and revision of adaptation strategies as climate learning proceeds will be necessary to ensure agricultural systems remain viable with climate change. Synergies between mitigation and adaptation planning are also possible through the use of coherent climate policy frameworks that link issues such as carbon sequestration, greenhouse gas emissions, land-use change, regional water management, and the long-term sustainability of production systems.

High adaptive capacity does not guarantee successful adaptation to climate change. Adaptation assessment and planning efforts routinely encounter conditions that limit adaptive action regardless of the adaptive capacity of the system under study. Potential constraints to adaptation can arise from ecological, social and economic conditions that are dynamic and vary greatly within and across economic sectors, communities, regions, and countries.

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Adapting agricultural systems to dramatic changes in the physical environment may be limited by social factors such as values, beliefs, or world views. Those factors can be affected by access to finance, political norms and values, and culture and religious ideologies.

Other limits to adaptation include the availability of critical inputs such as land and water, and constraints to farm financing and credit availability. These constraints may be substantial, especially for agricultural enterprises with little available capital or those without the financial capacity to withstand increasing variability of production and returns, including catastrophic loss. Differential capacity for adaptation, together with the variable effects of climate change on yield, creates significant concerns about agricultural productivity and food security…

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