finding 6.1 : agriculture-disrupted-by-climate

Climate disruptions to agricultural production have increased in the past 40 years and are projected to increase over the next 25 years. By mid-century and beyond, these impacts will be increasingly negative on most crops and livestock.

This finding is from chapter 6 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: A central component of the process was the development of a foundational technical input report (TIR), “Climate Change and Agriculture in the United States: An Assessment of Effects and Potential for Adaptation”.3baf471f-751f-4d68-9227-4197fdbb6e5d A public session conducted as part of the Tri-Societies ( meeting held in San Antonio, Texas, on Oct. 16-19, 2011, provided input to this report. The report team engaged in multiple technical discussions via teleconference, which included careful review of the foundational TIR3baf471f-751f-4d68-9227-4197fdbb6e5d and of approximately 56 additional technical inputs provided by the public, as well as other published literature and professional judgment. Discussions were followed by expert deliberation of draft key messages by the authors and targeted consultation with additional experts by the lead author of each message.

Description of evidence base: The key message and supporting text summarize extensive evidence documented in the Agriculture TIR, “Climate Change and Agriculture in the United States: An Assessment of Effects and Potential for Adaptation.3baf471f-751f-4d68-9227-4197fdbb6e5d Additional Technical Input Reports (56) on a wide range of topics were also received and reviewed as part of the Federal Register Notice solicitation for public input. Evidence that climate change has had and will have impacts on crops and livestock is based on numerous studies and is incontrovertible.c54b9473-cdc3-4f22-97a8-4df5253f9682 2c003dcb-ddfb-4415-8023-bb889cf9abea bf834846-f6f4-43be-ba39-5d77d592005f ab298c57-5dc2-4dc3-8e40-0737efa9d89c The literature strongly suggests that carbon dioxide, temperature, and precipitation affect livestock and crop production. Plants have an optimal temperature range to which they are adapted, and regional crop growth will be affected by shifts in that region’s temperatures relative to each crop’s optimal range. Large shifts in temperature can significantly affect seasonal biomass growth, while changes in the timing and intensity of extreme temperature effects are expected to negatively affect crop development during critical windows such as pollination. Crop production will also be affected by changing patterns of seasonal precipitation; extreme precipitation events are expected to occur more frequently and negatively affect production levels. Livestock production is directly affected by extreme temperature as the animal makes metabolic adjustments to cope with heat stress.3baf471f-751f-4d68-9227-4197fdbb6e5d Further, production costs in confined systems markedly increase when climate regulation is necessary.

New information and remaining uncertainties: Important new evidence (cited above) confirmed many of the findings in the past Synthesis and Assessment Product on agriculture,76db17ce-354b-4f0c-ad10-3e701c0387fc which informed the 2009 National Climate Assessment.e251f590-177e-4ba6-8ed1-6f68b5e54c8a There is insufficient understanding of the effects on crop production of rising carbon dioxide, changing temperatures and more variable precipitation patterns.a2704ef3-5be4-41ee-8dfa-4c82e416a292 The combined effects on plant water demand and soil water availability will be critical to understanding regional crop response. The role of increasing minimum temperatures on water demand and growth and senescence rates of plants is an important factor. There is insufficient understanding of how prolonged exposure of livestock to high or cold temperatures affects metabolism and reproductive variables.4192437a-d6c8-4b61-b051-8b2e0721279a For grazing animals, climate conditions during the growing season are critical in determining feed availability and quality on rangeland and pastureland.f2d332c1-eccb-4442-9036-b8bf9d586b17 The information base can be enhanced by evaluating crop growth and livestock production models. This evaluation would further the understanding of the interactions of climate variables and the biological system. Better understanding of projected changes in precipitation will narrow uncertainty about future yield reductions.a2704ef3-5be4-41ee-8dfa-4c82e416a292 f2d332c1-eccb-4442-9036-b8bf9d586b17

Assessment of confidence based on evidence: There are a range of controlled environment and field studies that provide the evidence for these findings. Confidence in this key message is therefore judged to be high.

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