Climate Change And Agriculture

DR. DENNIS B. EGLI

LEXINGTON, KENTUCKY

Stories of climate disasters dominated the recent news – too much water, not enough water, high temperatures and hurricanes. Are these disasters a preview of the future?

It is difficult to attribute any specific weather event to climate change, after all we had droughts, floods and hurricanes long before we started worrying about climate change. Some argue that extreme weather events are just fluctuations in the weather, implying that normal conditions will return in the future. We all know that weather fluctuates from day-to-day and  year-to-year, but the climate change occurring today is not a random fluctuation, it’s real. 

Climate change is driven by the greenhouse effect – greenhouse gases in the atmosphere (carbon dioxide, methane, nitrous oxides, and water vapor, of which carbon dioxide is the most important) act like a blanket over the earth, increasing temperature. The higher the concentration of greenhouse gases, the thicker the blanket, and the warmer the earth. Carbon dioxide concentrations in the atmosphere have increased from 280 ppm at the dawn of the industrial revolution in the early 1800s to more than 420 ppm today.

In all the debate about climate change, I have never heard anyone argue that the greenhouse effect, first discovered in the early 1800’s,  is not real. The greenhouse effect is increasing global temperatures (2023 was the hottest year in NOAA’s 174-year record of global temperatures) which will, in turn, affect all aspects of our weather, but we can’t predict exactly what the effect will be. We can, however, draw some general conclusions about how climate change might affect our grain-cropping systems. 

Let’s take the good news first. Higher levels of carbon dioxide in the atmosphere increase photosynthesis of crops that have C3-type photosynthesis (most crop species including soybean, wheat, rice canola and many forage species) which will increase their yields, unless other aspects of the environment are limiting. Unfortunately, plants with C4-type photosynthesis (corn, sorghum and millet) do not respond to higher carbon dioxide levels.

And now for the bad news. Temperatures above the optimum for plant growth will reduce photosynthesis and growth, which will, in turn, reduce yield. Really high temperatures interfere with pollination and seed set which can have catastrophic effects on crops where the seeds are harvested for yield (i.e., grain crops). 

Plants growing in higher temperatures will mature sooner and probably have shorter seed-filling periods. Shorter seed-filling periods produce smaller seeds and lower yields. Crops growing in environments where temperatures are below the optimum might benefit from rising temperatures until the temperatures pass the optimum. 

 It’s very likely that future crops will experience more water stress - too little or occasionally too much – as a result of climate change. Warm air holds more water vapor so we can expect more extreme, high-intensity rainfall events (think about hurricane Helene and western North Carolina) as temperatures increase.

Higher temperatures increase crop water use making it more likely that crops will run out of water during the growing season, thereby reducing yield. 

Higher temperatures could change weather patterns and cause reductions in rainfall and drought (think about the long-term drought and water scarcity problems in California). 

While we don’t know exactly how the weather and climate will change, there is no doubt, unless you claim that the greenhouse effect doesn’t exist, that the earth is warming, and our weather is changing. Can we adjust our crop production systems to minimize effects  of climate change on food production?

Warmer temperatures mean that the growing season will be longer, which will open areas at higher latitudes, where temperatures may be lower, for grain crop production. Longer growing seasons will also increase opportunities for double cropping. Growing soybean after winter wheat, common is Kentucky, has now spread to Northern Ohio and even Michigan. 

The longer growing season may make it possible to adjust planting dates and variety maturity (using earlier varieties with shorter growth cycles) of corn and soybean to minimize the effect of climate change by avoiding the highest temperatures and/or drought-prone periods (think about the success of the Early Soybean Production System (ESPS) - early varieties, planted early- in the Mid-South).

Plant breeders and geneticists are working to develop varieties that are more tolerant to high temperatures and moisture stress. Other scientists have suggested using crops that are not currently widely grown but have tolerance to high temperatures and water limitations (sorghum and millets for example).

These options may reduce the effects of climate change on crop productivity, but it is unlikely that they will provide long-term solutions. Adjusting to small increases in temperature or reductions in rainfall may be possible, but I don’t think we can manage our way around really catastrophic changes in the weather. For example, even drought tolerant crops can’t grow without some water.  Managing around long-term catastrophic drought, floods and heat waves, may be difficult. 

 The only long-term solution to climate change is to abandon fossil fuels, reduce emissions of greenhouse gases to essentially zero and lower the carbon dioxide concentration in the atmosphere to more reasonable levels. This is a huge challenge that will require major changes in agriculture and society, but it must, and it can be done. “Never doubt that a small group of thoughtful citizens can change the world.  Indeed, it is the only thing that ever has” (Margaret Mead, anthropologist, 1901 - 1978).  ∆

DR. DENNIS B. ELGI: University of Ketucky