Agricultural ecologist David Lobell talks climate change
“It’s not as simple as just shifting where the world’s crops are grown.”
January 22, 2016
David Lobell, an agricultural ecologist and an associate professor in Earth System Science at Stanford University, recently visited Cargill to discuss the latest research on the effects of climate change on agriculture. Here he shares some of his insights.
We’ve seen a number of significant storms, droughts and other weather events around the world in recent years. What do we know about the link between climate change and weather variability?
What we can say about rainfall is that we know it’s getting more intense. And an increase in the amount of really heavy rain events is very much predicted by a shift in the average temperature. What we find is that higher temperatures lead to increased water holding capacity in the air, which in turn leads to more intense rain events. Also what we’re seeing and what we expect to see are more really warm days and really warm nights. And we know that 2015 has been by far the warmest year on record. That’s different than saying we’re seeing increased variability in the climate in terms of temperature. There’s less evidence of things like increasing temperature swings from year to year.
So what does this mean for farmers?
For a farmer I think the most important thing going forward will be this shift in the average temperature. Even with a gradual change, if you’re relying on history or even very recent experience, you’re going to be more likely to err in your expectations about how to manage your crops and what you may encounter. One of the things farmers in the United States don’t realize is how much they have been spared some of the effects of climate change thus far relative to the rest of the world. Farmers in the Midwestern U.S. for a couple decades did not see a lot of climate change on a local level. But since 2012 that’s been changing. And it’s by no means certain that that relative stability is going to continue in the future.
What is one way a rise in average temperatures will affect farmers’ crops?
What people know but sometimes forget is how much more water you need to grow crops when temperatures rise. A lot of the crop stress we see in droughts is from temperature as much or more than it is from a lack of rainfall. One rule of thumb is that if crops grow at a certain rate at 25 degrees Celsius (77 degrees Fahrenheit), you’re losing water at about half the rate you would at 35 degrees Celsius (95 degrees Fahrenheit). It’s a very non-linear relationship. In reality, most of the places in the world where we grow corn, wheat and even soybeans are already experiencing higher-than-optimal temperatures for those crops.
Will this ultimately lead to crop production shifting toward higher latitudes? We already see corn being grown in areas like North Dakota where wheat once dominated.
It is true that as climate gets more attractive at higher latitudes you’ll see a shift in which crops are grown, so you might see a farmer grow more corn instead of wheat. But it’s also generally thought that the soils in these areas, on average, will be less optimal for a given crop than where they’re grown today and it may not prove to be as productive. So it’s not as simple as just shifting where the world’s crops are grown.
How might climate change impact food security beyond its direct effect on crops?
For many people in the world, hunger is driven more by a lack of income than by a lack of available food. And what has become clear from the research is that total economic productivity is a lot more sensitive to temperatures than is commonly appreciated. At warmer temperatures, the productivity of workers in general, and those working in agriculture in particular, goes down. That impact on economic growth is going to be really important for food security regardless of the direct impact on crop yields themselves. Unfortunately, the productivity in many warmer areas is expected to fall faster than in other places, including many of the poorest countries today. It’s going to become that much harder for those areas to compete.
This all sounds fairly bleak. To what extent do you believe farmers and the business community can innovate their way out of this problem?
Being concerned about climate change in no way diminishes the potential for humans to innovate and adapt, because we can. It’s important to stress that even in the most efficient agricultural systems we need continued innovation and progress regardless of climate change. The types of things we need are slightly different because of climate change, but not hugely different. Drought tolerance is always going to be beneficial. Heat tolerance has not been as beneficial historically, which is why it’s not a trait that we see in many crops, but it’s going to be increasingly important going forward. So innovation is absolutely key to adaptation and overcoming the effects of climate change. But at the same time, people shouldn’t think of innovation as something that eliminates the need to address climate change itself.