How farmers can adapt to a warming world

Global temperatures have not been this high in at least 4,000 years. The concentration of carbon dioxide in the atmosphere today – 400 parts per million – has not been this high for three million years. Climate change has moved from an abstract concept to a basic fact of nature, and scientists have been researching its effects on food production and prices.

The long-range forecasts are bleak, especially in developing countries. By 2050, climate change could cause irrigated wheat yields in some regions to fall by as much as 13 percent. Irrigated rice production could tumble 15 percent on average. In some parts of Africa, farmers growing maize could lose 10 to 20 percent of their crop.

It has been too easy for policy makers to seize upon the complexities of climate science as an excuse to avoid its realities, even as global food prices prove to be as volatile as the weather. However, we now have the tools and knowledge needed to act and make solid decisions. A growing number of governments have grasped the magnitude of the problem and are working to ensure their farmers can handle the continuing evolution of our planet’s seasons.

These forward-thinking governments have taken the crucial first step, cutting through uncertainty using tools and knowledge already available. These countries have embraced “no-regrets” adaptation: actions that will benefit farmers and society regardless of specifically how and when climate change plays out on the ground.

Collecting rainwater in Sri Lanka

In Sri Lanka, the agriculture sector plays an important role in the national economy, employing about a third of the population and producing about an eighth of the gross domestic product. But climate change projections for the country differ wildly and do not offer a useful starting point for policy makers trying to form adaptation strategies.

The projections show average temperatures across the country increasing, though the projections differ on whether rainfall will increase or decrease. The Sri Lankan government looked instead at historical data that revealed regions that are more vulnerable to water problems. Using this approach, the country’s limited resources were directed to those who need support the most.

Countries have made progress on climate-resilient agriculture by focusing on what is known rather than what remains unclear.

Then, drawing on the existing capacity of farmers and local governments in those regions, experts devised an adaptation strategy built on technologies that have worked for centuries. Ancient Sri Lankan kingdoms used large above-ground tanks to collect rainwater for use later in the season; modern-day farmers are now using this technique with great success. Farmers are also reusing their household wastewater and scaling back groundwater use to sustainable levels. “No-regrets” adaptation has started with actions that make farming more sustainable. Sri Lankan farmers and the people they feed all benefit.

Arabica coffee’s narrow niche

In Nicaragua, coffee makes up approximately one quarter of national agricultural export revenues. While Arabica coffee is a primary source of income for smallholder farmers, it is a crop that can only grow in a narrow band of precipitation and temperature. The plant, which produces higher-value beans for specialty coffee manufacturers and their markets, requires mean temperatures of 19 to 22 degrees Celsius with little variation and ample rainfall.

In the ideal planning scenario, policymakers would have a number of future variables pinned down with certainty.  Individual climate models for Nicaragua tell completely different stories. But a common thread emerges when you look at the models together, one that can provide clear guidance for best practice at different altitudes. As temperatures rise, only higher-altitude zones will be suitable for the crop. In many places, the crop will simply run out of mountain to climb.

The “no-regrets” adaptation option for most of the land where Arabica coffee is grown is clear – it is time to switch to a different crop. At lower altitudes, cocoa is a crop with a similar cash value to coffee but better suited to the new growing conditions. At higher altitudes that are becoming newly suitable for coffee, the environmental impacts of the crop are considered too harmful. In between the two altitude ranges, farmers will have to adjust their agricultural practices as the climate changes, for example by introducing shade-grown varieties.

Patterns amid uncertainty

In these examples, countries have made progress on climate-resilient agriculture by focusing on what is known rather than what remains unclear. Computer models can be used to estimate climate impacts on a range of timescales. Models can predict areas of crop failure in West Africa a few months ahead of the harvest, for example. On longer timescales, models show that northeast China’s wheat-growing regions will need more heat-tolerant crops within a few decades. This kind of knowledge helps us select adaptation strategies with confidence despite many remaining uncertainties about the future.

It is not just heat stress that is important. Low-lying coastal rice-growing regions should prepare for more saline conditions fed by a rise in sea level. Areas plagued by drought should sustainably tap their groundwater rather than deplete it. In parts of Texas, Oklahoma and Kansas, for example, maize farmers could switch to sorghum and other less water-intensive crops where groundwater depletion has made irrigation more difficult.

Scientists are learning to communicate climate predictions and uncertainties in ways that are more useful to planners and policymakers. It is more helpful to say when a particular change is likely to happen – “starting sometime between 2020 and 2040, there won’t be enough rain here to grow vegetables without irrigation” – than to give a string of probabilities linked to distant futures. All of society – especially farmers – needs to know when specific changes are needed.

As the amount of greenhouse gases in our atmosphere continues to increase, the effects of climate change on agriculture will become increasingly visible. It is urgent to adjust or even transform agriculture even if our knowledge is incomplete. The science of adaptation has matured enough for us to make robust adaptation plans based on what we do know. It is time to embrace and deploy this science and start figuring out how we will feed ourselves in the future.

Sonja Vermeulen and Andy Challinor are lead authors of Addressing Uncertainty in Adaptation Planning for Agriculture, a study published online at PNAS.org (the Proceeding of the National Academy of Sciences of the United States). 

Dr Vermeulen is the Head of Research for the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).

Dr Challinor is a professor at the Institute for Climate and Atmosphere Science, School of Earth and Environment at the University of Leeds, and co-leads research on climate adaptation in CCAFS.