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Climate change affects all segments of the agricultural enterprise, and there is mounting evidence that the continuing warming trend with shifting seasonality and intensity in precipitation will increase the vulnerability of agricultural systems. Agricultural is a complex system within the USA encompassing a large number of crops and livestock systems, and development of indicators to provide a signal of the impact of climate change on these different systems would be beneficial to the development of strategies for effective adaptation practices. A series of indicators were assembled to determine their potential for assessing agricultural response to climate change in the near term and long term and those with immediate capability of being implemented and those requiring more development. The available literature reveals indicators on livestock related to heat stress, soil erosion related Climatic Change

Food Security and Food Production SystemsChapter 7On average, agronomic adaptation improves yields by the equivalent of ~15-18% of current yields {Figure 7-8, Table 7-2}, but the effectiveness of adaptation is highly variable (medium confidence) ranging from potential dis-benefits to negligible to very substantial (medium confidence). {7.5.1.1.1} Projected benefits of adaptation are greater for crops in temperate, rather than tropical, regions (medium confidence) {7.5.1.1.1, Figures 7-4, 7-7}, with wheat-and rice-based systems more adaptable than those of maize (low confidence).{Figure 7-4} Some adaptation options are more effective than others (medium confidence). {Table 7-2}Global temperature increases of ~4°C or more above late-20th-century levels, combined with increasing food demand, would pose large risks to food security globally and regionally (high confidence). Risks to food security are generally greater in lowlatitude areas. {Box 7-1, Table 7-3, Figures 7-4, 7-5, 7-7} Changes in temperature and precipitation, without considering effects of CO 2 , will contribute to increased global food prices by 2050, with estimated increases ranging from 3 to 84% (medium confidence). Projections that include the effects of CO 2 changes, but ignore O 3 and pest and disease impacts, indicate that global price increases are about as likely as not, with a range of projected impacts from -30% to +45% by 2050. {7.4.4}Adaptation in fisheries, aquaculture, and livestock production will potentially be strengthened by adoption of multi-level adaptive strategies to minimize negative impacts. Key adaptations for fisheries and aquaculture include policy and management to maintain ecosystems in a state that is resilient to change, enabling occupational flexibility, and development of early warning systems for extreme events (medium confidence). {7.5.1.1.2} Adaptations for livestock systems center on adjusting management to the available resources, using breeds better adapted to the prevailing climate and removing barriers to adaptation such as improving credit access (medium confidence). {7.5.1.1.3}A range of potential adaptation options exist across all food system activities, not just in food production, but benefits from potential innovations in food processing, packaging, transport, storage, and trade are insufficiently researched. {7.

Reich et al . (Reports, 20 April 2018, p. 317) assert that the responses of C 3 and C 4 grass biomass to elevated CO 2 “challenge the current C 3 -C 4 [elevated CO 2 ] paradigm,” but these responses can be explained by the natural history of the experimental plants and soils without challenging this paradigm.

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