Challenges to human and livestock health are growing due to the increased frequency and intensity of high temperature extremes (very likely, high confidence). Extreme heat conditions contribute to heat exhaustion, heatstroke, and heart attacks in humans (very likely, high confidence). Heat stress in livestock results in large economic losses for producers (very likely, high confidence). Expanded health services in rural areas, heat-tolerant livestock, and improved design of confined animal housing are all important advances to minimize these challenges.

This finding is from chapter 10 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

Each regional author team organized a stakeholder engagement process to identify the highest-priority concerns, including priorities for agriculture and rural communities. Due to the heterogeneous nature of agriculture and rural communities, the national chapter leads (NCLs) and coauthor team put in place a structured process to gather and synthesize input from the regional stakeholder meetings. Where possible, one or more of the authors or the chapter lead author listened to stakeholder input during regional stakeholder listening sessions. Information about agriculture and rural communities was synthesized from the written reports from each regional engagement workshop. During the all-authors meeting on April 2–3, 2017, the NCL met with authors from each region and other national author teams to identify issues relevant to this chapter. To finalize our regional roll-up, a teleconference was scheduled with each regional author team to discuss agriculture and rural community issues. Most of the regional author teams identified issues related to agricultural productivity, with underlying topics dominated by drought, temperature, and changing seasonality. Grassland wildfire was identified as a concern in the Northern and Southern Great Plains. All regional author teams identified soil and water vulnerabilities as concerns, particularly as they relate to soil and water quality impacts and a depleting water supply, as well as reduced field operation days due to wet soils and an increased risk of soil erosion due to precipitation on frozen soil. Heat stress in rural communities and among agricultural workers was of concern in the Southeast, Southern Great Plains, Northwest, Hawaiʻi and Pacific Islands, U.S. Caribbean, and Northeast. Livestock health was identified as a concern in the Northeast, Midwest, U.S. Caribbean, and Southern Great Plains. Additional health-related concerns were smoke from wildfire, pesticide impacts, allergens, changing disease vectors, and mental health issues related to disasters and climate change. Issues related to the vulnerability and adaptive capacity of rural communities were identified by all regions. Discussions with the regional teams were followed by expert deliberation on the draft Key Messages by the authors and targeted consultation with additional experts. Information was then synthesized into Key Messages, which were refined based on published literature and professional judgment.

Description of evidence base:

The Key Message and supporting text summarize extensive evidence documented in the USGCRP’s Climate Science Special Report.75cf1c0b-cc62-4ca4-96a7-082afdfe2ab1

Humans: Houghton et al. (2017)ced8505a-f36f-4c7b-8a0d-ec7f08482297 synthesize the literature that presents strong evidence of climate change impacts on human health in rural areas. Anderson et al. (2018)200c4ff2-90da-45da-bc7a-f4565dbd2fbb find that heat waves pose risks to human mortality but that the risk associated with any single heat wave depends on many factors, including heat wave length, timing, and intensity. On average, heat waves increase daily mortality risk by approximately 4% in the United States,a6714dce-b324-4324-a88e-d31d31fa2d95 but extreme heat waves present significantly higher risks. While research on heat-related morbidity has focused on urban areas, Jagai et al. (2017)e518fff1-caa5-4ed1-8fdc-b512da7cbe3b analyzed heat waves in Illinois over 1987–2014 and found that there were 1.16 hospitalizations per 100,000 people in the most rural, thinly populated areas, compared to 0.45 hospitalizations per 100,000 in metropolitan areas. Consequently, a 1.8°F (1°C) increase in maximum monthly temperature was associated with a 0.34 increase in hospitalization rates in rural areas compared to an increase of 0.02 per 100,000 in urbanized counties. The mean cost per hospital stay was $20,050. Fechter-Leggett et al. (2016),9d4b4e3f-1739-4e8f-ab0b-610dd5276da3 Hess et al. (2014),7d16ea3a-c4dc-4ebd-8d38-c3d6a64a3e66 and Sugg et al. (2016)a0403ee4-f787-4078-bcba-64cdd6cc9cb1 also report an elevated risk in rural areas for emergency room visits for heat stress. Additionally, rural areas have a high proportion of outdoor workers who are at additional risk for heat stress.e518fff1-caa5-4ed1-8fdc-b512da7cbe3b^,79a8b35d-8f50-44c3-ba7d-a8c76f407620^,26779560-dc50-4a6b-b555-d4075ce16af9 Merte (2017)c97a2716-9162-4e1d-ad39-ca1589a8d760 analyzed data from 1960 to 2015 for 27 European countries and found that 0.61% of all deaths were caused by extreme heat.

New information and remaining uncertainties:

Humans: Much of the literature focuses on heat-related mortality in urban areas (e.g., Oleson et al. 2015; Marsha et al. 2017a5d430bc-5756-42d1-924f-3dbc927e69c4^,8e30bef3-ce8e-4df4-879b-21f809b02998). Vulnerability and exposure in rural areas are not well understood, but Oleson et al. (2015),a5d430bc-5756-42d1-924f-3dbc927e69c4 in quantifying projected future temperature impacts, indicate that urban areas will experience more summer heat days and reduced winter cold temperature days than rural areas. Huber et al. (2017)2d3fe667-e18a-42ca-abf6-ae5261ac54e1 identify uncertainties in estimated impacts of death from cardiovascular diseases from a 1.8°F (1°C) increase in global temperature. Anderson et al. (2018)200c4ff2-90da-45da-bc7a-f4565dbd2fbb discuss uncertainties associated with changes in the size and age of the population and the breadth of plausible socioeconomic scenarios. Jones et al. (2015)7e3a9127-81cd-46bf-99b8-e3538e982fea identify uncertainties in the migration of population due to a changing climate and how that would impact exposure. Hallstrom et al. (2017)aa5c6ab0-74a3-40c4-83a3-0093480b9603 evaluated the possible effects of future diet choices on various health indicators, many of which would have impacts on an individual’s sensitivity to high temperature.

Livestock: Walthall et al. (2012)3baf471f-751f-4d68-9227-4197fdbb6e5d synthesize a wide body of literature that documents the impacts of extreme temperature effects on livestock health and productivity. Ruminant livestock support rural livelihoods and produce high-quality food products from land that is otherwise unsuited to crop agriculture.831b4c27-416e-4b98-94e6-3969a3b34031^,d812667f-d643-497f-b969-be0acd154c4d

Assessment of confidence based on evidence:

Extreme temperatures are projected to increase even more than average temperatures. The temperatures of extremely cold days and extremely warm days are both projected to increase. Cold waves are projected to become less intense, while heat waves will become more intense (very likely, very high confidence).29960c69-6168-4fb0-9af0-d50bdd91acd3

Lehner et al. (2017)53448a8f-22bd-4111-8212-b2204e4d4864 indicate a high likelihood and high confidence that there will be increased record-breaking summer temperatures by the end of the century. Evidence of challenges to human and livestock health due to temperature extremes is well established (very likely, very high confidence).