There’s bad news and good news for agriculture in the Fourth National Climate Assessment released by federal officials last week on Black Friday.
The report predicts that temperature increases and changes in precipitation patterns could adversely impact agriculture in many areas of the country. The report identifies this as largely due to an increase in manmade greenhouse gasses. The good news: Farmers can use tools to help mitigate any negative impacts.
What it is
The assessment is part of the Global Change Research Act of 1990, which mandates that the U.S. Global Change Research Program (USGCRP) deliver a report to Congress and the President at least every four years.
It’s the work of more than 300 federal and nonfederal experts – including individuals from federal, state, and local governments; tribes and indigenous communities; national laboratories; universities; and the private sector – who volunteer their time to produce the peer-reviewed assessment. These individuals also receive input from external stakeholders at each stage of the process.
The report, which contains over 1,600 pages, cites global atmospheric carbon dioxide (CO2) concentration that’s now 400 parts per million (ppm) as a major factor in changing climate. The researchers say the last time this level occurred was about 3 million years ago, when both global average temperature and sea level were significantly higher than today.
The researchers state that continued growth in CO2 over this century and beyond will lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. There is broad consensus that the further and the faster the Earth system is pushed toward warming, the greater the risk of unanticipated changes and impacts, some of which are potentially large and irreversible, say the report’s authors.
All this has helped fuel global climate above the pace of natural variations in climate that have occurred throughout Earth’s history. Global average temperature has increased by about 1.8°F. from 1901 to 2016, and observational evidence does not support any credible natural explanations for this amount of warming, say the report’s authors. Instead, the evidence consistently points to human activities – especially emissions of greenhouse or heat-trapping gases – as the dominant cause.
Under scenarios with high emissions and limited or no adaptation, annual losses in some sectors are estimated to grow to hundreds of billions of dollars by the end of the century. It is very likely that some physical and ecological impacts will be irreversible for thousands of years, while others will be permanent, the report states.
What farmers can expect in the future
• Long-term temperature increases will decrease average yields of many commodity crops including corn, soybean, wheat, rice, sorghum, cotton, oats, and silage due to rising atmospheric carbon dioxide levels.
Conversely, future yields for crops like wheat, hay, and barley may increase even with warmer temperatures in areas like the north-central United States, due to anticipated increases in precipitation and carbon fertilization. Overall, though, U.S. yields for commodity crops are expected to decline as a consequence of higher temperatures, particularly if they occur during critical periods of reproductive development.
• Warmer Temperatures Will Impact Livestock and Poultry, Too
Rising temperatures will also place greater stress on livestock and poultry, although the report says severity will vary by region. Heat stress in livestock and poultry changes respiration rate, heart rate, blood chemistry, hormones, and metabolism. Animals also change behavior, such as increasing water intake and reducing feed intake. Heat stress also affects reproductive efficiency.
Dairy cows are particularly sensitive to heat stress, as it negatively affects their appetite, rumen fermentation, and lactation yield. Frequent higher temperatures also lower milk quality (reduced fat, lactose, and protein percentages).
The report cites a study indicating the dairy industry expects production declines related to heat stress of 0.60% to 1.35% for the average dairy over the next 12 years, with larger declines in the Southern Great Plains and the Southeast due to increasing relative stress. (This assumes producing regional herd inventories remain stable.)
Confinement systems for many pork and poultry producers feature environmentally controlled facilities that lessen the impact of temperature extremes on production efficiencies. However, these systems rely on mechanized cooling systems that are more expensive to operate as temperatures increase and are subject to extreme losses associated with the failures of cooling equipment.
The good news is that adaptation strategies are possible to a degree. They include:
• Livestock being genetically adapted to local conditions.
• Feed rations that help livestock better endure heat stress.
• Installation of permanent or portable shading structures and/or planting trees. Studies have shown that shading in combination with fans and sprinkler or evaporative cooling technologies can mitigate the short-term effects of heat stress on animal production and reproductive efficiency.
• Alignment of feeding and management practices with the cooler times of the day and reducing the effort required by animals to access food and water.
* Precipitation Patterns Will Change
Good news for farmers in the north-central U.S. Increased precipitation may remove part of the sting of increased temperatures. For 2070-2099 relative to 1986-2015, precipitation will increase up to 20% during the winter and spring for the north-central U.S. In Alaska, precipitation during these times is expected to increase more than 30%.
Meanwhile, spring precipitation is projected to decrease by 20% or more in the Southwest in spring. In summer, a slight decrease is projected across the Great Plains, with little to no net change in fall.
* The Bad News: Precipitation Will Be More Intense
It’s not your imagination if it seems those 5-inch-in-an-hour downpours are becoming more frequent. They are.
The report found that heavy precipitation is becoming more intense and more frequent across most of the U.S., particularly in the Northeast and Midwest. The researchers project these trends will continue in the future.
* Climate Change Will Impact the Ogallala Aquifer Region (OAR)
The OAR underlies the Great Plains, one of the most productive farm belts in the world. Irrigated agriculture uses more than 95% of the groundwater extracted from the Ogallala Aquifer, and the economy of the region depends almost entirely on irrigated agriculture.
The aquifer has been pressured before. Converting native grasslands to crops in the early 1900s led to the severe dust storms that became known as the Dust Bowl of the 1930s. Adopting soil conservation methods and irrigation with Ogallala water improved soil health and reduced soil erosion while expanding the region’s economy.
However, report researchers say major portions of the Ogallala Aquifer should now be considered a nonrenewable resource. Reduced well outputs due to excessive pumping, especially in central and southern parts of the OAR – coupled with frequent and prolonged droughts – have led to recent dust storms that were similar to those of the 1930s and 1950s. Climate change is projected to further increase the duration and intensity of drought over much of the OAR in the next 50 years.
* There’s some good news for OAR irrigators
Drought resilience can be improved by adopting high-efficiency precision irrigation technologies, say the report’s authors. In order for these systems to work effectively, a network of weather stations is required in agricultural regions. Currently, 23 states have one or more publicly funded agricultural weather networks, such as the Oklahoma Mesonet and the Nebraska Agricultural Water Management Network.
* Weeds Will Thrive
Carbon dioxide is a critical part of photosynthesis needed for plants to thrive. Some crops, such as potatoes, thrive when atmospheric CO2 and temperature rise.
The bad news: Weeds like it, too, and the increase in rising atmospheric CO2 concentrations, elevated temperatures, and other climate changes will enhance weed competitiveness relative to crops.
* Wildfires Will Increase in Frequency and Length
Wildfires play a normal and natural role in managing forests and rangeland ecosystems. However, climate change threatens to increase the frequency and length of the wildfire season, as well as the size and extent of large fires. Increasing temperatures also promote an increased spread of invasive or encroaching species, which exacerbate wildfire risks.
* Worldwide Food Security is at Risk
The report states that many countries are already experiencing rapid price increases for basic food commodities, mainly due to production losses associated with more frequent weather extremes and unpredictable weather events. This is compounded by projected population growth and potential changes in diets as the world seeks to feed a projected 9.8 billion people by 2050.