2014/07/16 Council Agenda Packet

21: NORTHWEST in the Northwest than in certain other regions, sustainability of some Northwest agricultural sectors is threatened by soil Description of Observed Northwest agriculture's sensitivity to climate change stems from its dependence on irrigation water, a specific range of temperatures, precipitation, and growing seasons, and the sensitivity of crops to temperature extremes. Projected warming will reduce the availability of irrigation water in snowmelt-fed basins and increase the probability of heat stress to field crops and tree fruit. Some crops will benefit from a longer growing season115 and/or higher atmospheric carbon dioxide, at least for a few decades.115'116 Longer -term consequences are less certain. Changes in plant diseases, erosion114 and water supply uncertainty, both of which could be exacerbated by climate change. and Projected Changes pests, and weeds present additional potential risks. Higher average temperatures generally can exacerbate pest pressure through expanded geographic ranges, earlier emergence or arrival, and increased numbers of pest generations (for example, Ch. 6: Agriculture).117 Specifics differ among pathogen and pest species and depend upon multiple interactions (Ch. 6: Agriculture)118 preventing region -wide generalizations. Research is needed to project changes in vulnerabilities to pest, disease, and weed complexes for specific cropping systems in the Northwest. Consequences of Changes Because much of the Northwest has low annual precipitation, many crops require irrigation. Reduction in summer flows in snow -fed rivers (see Figure 21.2), coupled with warming that could increase agricultural and other demands, potentially produces irrigation water shortages.108 The risk of a water - short year — when Yakima basin junior water rights holders are allowed only 75% of their water right amount — is projected to increase from 14% in the late 20`h century to 32% by 2020 and 77% by 2080, assuming no adaptation and under the A1B scenario.46 Assuming adequate nutrients and excluding effects of pests, weeds, and diseases, projected increases in average temperature and hot weather episodes and decreases in summer soil moisture would reduce yields of spring and winter wheat in rain -fed production zones of Washington State by the end of this century by as much as 25% relative to 1975 to 2005. However, carbon dioxide fertilization should offset these effects, producing net yield increases as great as 33% by 2080.115 Similarly, for irrigated potatoes in Washington State, carbon dioxide fertilization is projected to mostly offset direct climate change related yield losses, although yields are still projected to decline by 2% to 3% under the A1B emissions scenario.115 Higher temperatures could also reduce potato tuber quality."" Irrigated apple production is projected to increase in Washington State by 6% in the 2020s, 9% in the 2040s, and 16% in the 2080s (relative to 1975 to 2005) when offsetting effects of carbon dioxide fertilization are included,ils However, because tree fruit requires chilling to ensure uniform flowering and fruit set and wine grape varieties have specific chilling requirements for maturation,'2° warming could adversely affect currently grown varieties of these commodities. Most published projections of climate change impacts on Northwest agriculture are limited to Washington State and have focused on major commodities, although more than 300 crops are grown in the region. More studies are needed to identify the implications of climate change for additional cropping systems and locations within the region. The economic consequences for Northwest agriculture will be influenced by input and output prices driven by global economic conditions as well as by regional and local changes in productivity. Adaptive Capacity and Implications for Vulnerability Of the four areas of concern discussed here, agriculture is perhaps best positioned to adapt to climate trends without explicit planning and policy, because it already responds to annual climate variations and exploits a wide range of existing climates across the landscape.121 Some projected changes in climate, including warmer winters, longer annual frost - free periods, and relatively unchanged or increased winter precipitation, could be beneficial to some agriculture systems. Nonetheless, rapid climate change could present difficulties. Adaptation could occur slowly if substantial investments or significant changes in farm operations and equipment are required. Shifts to new varieties of wine grapes and tree fruit, if indicated, and even if ultimately more profitable, are necessarily slow and expensive. Breeding for drought- and heat -resistance requires long-term effort. Irrigation water shortages that necessitate shifts away from more profitable commodities could exact economic penalties.lo8 U.S. GLOBAL CHANGE RESEARCH PROGRAM 497 CLIMATE CHANGE IMPACTS IN THE UNITED STATES