Climate change is affecting the natural environment, agriculture, energy production and use, land and water resources, transportation, and human health and welfare across the U.S. and its territories, warns a federal report released on November 23. The second volume of the “Fourth National Climate Assessment” (NCA4), published by the United States Global Change Research Program, was compiled by more than 300 experts, including individuals from federal, state, and local governments, indigenous communities, national laboratories, universities, and the private sector. The report concludes that “the evidence of human-caused climate change is overwhelming and continues to strengthen, that the impacts of climate change are intensifying across the country, and that climate-related threats to Americans’ physical, social, and economic well-being are rising.” According to the authors, these impacts are projected to intensify, but how much they intensify will depend on actions taken to reduce global greenhouse gas emissions and to adapt to the risks from climate change now and in the coming decades.

With respect to agriculture and food, the report says that rising temperatures, extreme heat, drought, wildfire on rangelands and heavy downpours are expected to increasingly challenge the quality and quantity of U.S. crop yields, livestock health, price stability and rural livelihoods. The first key message of chapter 10 on agriculture and rural communities is that agricultural productivity will decrease. “Food and forage production will decline in regions experiencing increased frequency and duration of drought. Shifting precipitation patterns, when associated with high temperatures, will intensify wildfires that reduce forage on rangelands, accelerate the depletion of water supplies for irrigation, and expand the distribution and incidence of pests and diseases for crops and livestock,” says the report. The authors also warn against the degradation of soil and water resources. “The degradation of critical soil and water resources will expand as extreme precipitation events increase across our agricultural landscape. Sustainable crop production is threatened by excessive runoff, leaching, and flooding, which results in soil erosion, degraded water quality in lakes and streams, and damage to rural community infrastructure.” The experts stress that management practices to restore soil structure and the hydrologic function of landscapes are essential for improving resilience to these challenges.

The third key message is that high temperature extremes will pose enormous challenges to human and livestock health. “Extreme heat conditions contribute to heat exhaustion, heatstroke, and heart attacks in humans. Heat stress in livestock will result in large economic losses for producers. The authors also warn that residents in rural communities often have limited capacity to respond to climate change impacts, due to poverty and limitations in community resources. According to chapter 21 of the assessment, climate change is expected to have wide-ranging impacts on the Midwest. “The Midwest is a major producer of a wide range of food and animal feed for national consumption and international trade. Increases in warm-season absolute humidity and precipitation have eroded soils, created favorable conditions for pests and pathogens, and degraded the quality of stored grain.” The scientists found rising temperatures and more frequent, intense rains are likely to reduce agricultural production in the Midwest to levels seen in the 1980s by 2050. Commodity crops like corn could see reduced yields of 5 to over 25% across the Midwest.

“How many wake-up calls do we need?” said Carol Werner, Executive Director of the Environmental and Energy Study Institute (EESI). “Every new National Climate Assessment has built on the previous one, confirming that climate change is already happening, and that we need to act,” she added. “Time is running out.” The Trump administration released the report on Black Friday, when Americans traditionally go shopping and spend time with their families, a date that critics said was chosen to bury the report. President Trump told reporters on Monday: “I’ve seen it. I’ve read some of it. I don’t believe it.” He said it makes no sense for the United States to take drastic steps to combat climate change when other countries, such as China and Japan, do not address climate change. “Right now we’re at the cleanest we’ve ever been. It’s very important to me,” Trump added. “But if we’re clean but every other place on earth is dirty, that’s not so good,” he continued. (ab)