Many agricultural regions will experience declines in crop and livestock production from increased stress due to weeds, diseases, insect pests, and other climate change induced stresses.

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 (https://www.acsmeetings.org/home) 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 summarizes 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. Numerous peer-reviewed publications describe the direct effects of climate on the ecological systems within which crop and livestock operations occur. Many weeds respond more strongly to CO2 than do crops, and it is believed that the range of many diseases and pests (for both crop and livestock) will expand under warming conditions.b8d97f08-9215-4ff3-b2fe-76b4e8eb0170 c1a43145-46ee-4b21-865e-6ed5b98c2f0d 4986bca7-f0d4-4926-b05d-a005bb63a1f3 Pests may have increased overwinter survival and fit more generations into a single year, which may also facilitate faster evolution of pesticide resistance. Changing patterns of pressure from weeds, other pests, and disease can affect crop and livestock production in ways that may be costly or challenging to address.a2704ef3-5be4-41ee-8dfa-4c82e416a292 3baf471f-751f-4d68-9227-4197fdbb6e5d

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 In addition to extant species already in the U.S., exotic weeds, diseases, and pests have particular significance in that: 1) they can often be invasive (that is, arrive without normal biological/ecological controls) and highly damaging; 2) with increasing international trade, there are numerous high-threat, high-impact species that will arrive on commodities from areas where some species even now are barely known to modern science, but which have the potential to emerge under a changed climate regime to pose significant risk of establishment in the U.S. and economic loss; and 3) can take advantage of “disturbances,” where climate variability acts as an additional ecological disturbance. Improved models and observational data related to how many agricultural regions will experience declines in animal and plant production from increased stress due to weeds, diseases, insect pests, and other climate change induced stresses will need to be developed. A key issue is the extent of the interaction between components of the natural biological system (for example, pests) and the economic biological system (for example, crop or animal). For insects, increased populations are a factor; however, their effect on the plant may be dependent upon the phenological stage of the plant when the insect is at specific phenological stages.3baf471f-751f-4d68-9227-4197fdbb6e5d To enhance our understanding of these issues will require a concerted effort to begin to quantify the interactions of pests and the economic crop or livestock system and how each system and their interactions are affected by climate.3baf471f-751f-4d68-9227-4197fdbb6e5d

Assessment of confidence based on evidence: The scientific literature is beginning to emerge; however, there are still some unknowns about the effects of biotic stresses, and there may well be emergent “surprises” resulting from departures from past ecological equilibria. Confidence is therefore judged to be medium that many agricultural regions will experience declines in animal and plant production from increased stress due to weeds, diseases, insect pests, and other climate change induced stresses.

References :

• Changes in competitive ability between a C4 crop and a C3 weed with elevated carbon dioxide (c1a43145)
• Global change, global trade, and the next wave of plant invasions (4986bca7)
• SAP 4.3. The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity. (76db17ce)
• Climate Impacts on Agriculture: Implications for Crop Production (a2704ef3)
• Evaluation of the growth response of six invasive species to past, present and future atmospheric carbon dioxide (b8d97f08)
• Climate Change and Agriculture in the United States: Effects and Adaptation. USDA Technical Bulletin 1935 (3baf471f)
• Global Climate Change Impacts in the United States (e251f590)