finding 19.2 : growth-cycles-change-agriculture

Changes to crop growth cycles due to warming winters and alterations in the timing and magnitude of rainfall events have already been observed; as these trends continue, they will require new agriculture and livestock management practices.



This finding is from chapter 19 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: A central component of the assessment process was the Great Plains Regional Climate assessment workshop that was held in August 2011 in Denver, CO, with approximately 40 attendees. The workshop began the process leading to a foundational Technical Input Report (TIR), the Great Plains Regional Climate Assessment Technical Report.5552509e-9af3-46dd-8920-78083bee05bc The TIR consists of 18 chapters assembled by 37 authors representing a wide range of inputs including governmental agencies, non-governmental organizations, tribes, and other entities. The chapter author team engaged in multiple technical discussions via regular teleconferences. These included careful review of the foundational TIRd873710b-8d1f-43fa-bb4f-2ffe216c089c and of approximately 50 additional technical inputs provided by the public, as well as the other published literature, and professional judgment. These discussions were followed by expert deliberation of draft key messages by the authors during an in-person meeting in Kansas City in April 2012, wherein each message was defended before the entire author team prior to the key message being selected for inclusion in the report. These discussions were supported by targeted consultation with additional experts by the lead author of each message, and they were based on criteria that help define “key vulnerabilities”.

Description of evidence base: The key message and supporting text summarize extensive evidence documented in the Great Plains Technical Input Report.5552509e-9af3-46dd-8920-78083bee05bc Technical inputs (47) on a wide range of topics were also received and reviewed as part of the Federal Register Notice solicitation for public input. Evidence for altered precipitation across the U.S. is discussed in Ch. 2: Our Changing Climate, Key Message 5 and 6 and their Traceable Accounts. Specific details for the Great Plains, such as warming winters and altered rainfall events are in the Climate Trends and Scenarios for the U.S. National Climate Assessment994416dc-705b-4063-b8f5-bd3ed21d4a71 with its references. Limitations of irrigation options in the High Plains aquifer have been detailed.c3b3f3ee-e9f3-442b-99a1-aca0976cf3b5 The impacts of shifting from irrigated to rain-fed agriculture have also been detailed.46a54a3a-dd83-4f37-be2f-c1e809a02ea8 Studies document negative impacts on livestock production through the Great Plains.6dd5147a-03da-4c2c-b3dd-917d2d856a1a 3b640ac2-c259-436d-bcae-4bd37bf30c0f

New information and remaining uncertainties: A key issue (uncertainty) is rainfall patterns. Although models show a general increase in the northern Great Plains and a decrease in the southern Great Plains, the diffuse gradient between the two leaves uncertain the location of greatest impacts on the hydrologic cycle. Timing of precipitation is critical to crop planting, development and harvesting; shifts in seasonality of precipitation therefore need to be quantified. Rainfall patterns will similarly affect forage production, particularly winter wheat that is essential to cattle production in the southern Great Plains.

Assessment of confidence based on evidence: The general pattern of precipitation changes and overall increases in temperature are robust. The implications of these changes are enormous, although assessing changes in more specific locations is more uncertain. Our assessment is based on the climate projections and known relationships to crops (for example, corn not being able to “rest” at night due to high minimum temperatures), but pinpointing where these impacts will occur is difficult. Additionally, other factors that influence productivity, such as genetics, technological change, economic incentives, and federal and state policies, can alter or accelerate the impacts. Given the evidence and remaining uncertainties, agriculture and livestock management practices will need to adjust to these changes in climate and derived aspects although specific changes are yet to be determined. Overall, confidence is high.

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