Climate change and agricultural impacts will increase inequality

Dramatic changes in crop productivity will be felt globally in the next 10 years — a decade earlier than previously thought — according to new computer simulations recently published in Nature Food.

The studyClimate change will lead to significant yield reductions for crops such as corn and soy by 2100, according to the study. The study warns that agriculture will change in key breadbasket areas such as the United States, Middle East, Central Asia and China much sooner than previously thought. The research effort was led by Jonas Jägermeyr at the NASA Goddard Institute for Space Studies in New York, in collaboration with researchers at Germany’s Potsdam Institute for Climate Impacts Research (PIK).

Scientists combined five new climate models from the World Climate Research Programme’s Coupled Model Intercomparison Project(CMIP), which includes twelve global crop models that allow for the most accurate and comprehensive set of crop yield simulations. They used known processes from plant physiology and ecology as a basis to predict corn, wheat and rice yields in two climate scenarios. One was very high-emissions (RCP8.5), the other was climate mitigation (RCP2.6). They found that corn (maize) — a staple crop in sub-Saharan Africa, Southeast Asia, and Latin America and the world’s most popular grain — could experience yield declines of up to 24% by the end of the century. Over the same time, wheat could see a 17% increase in productivity.

Climate impacts emerging

The researchers gauged how soon climate impacts on agricultural productivity might emerge in different regions using a statistical measure known as time of climate impact emergence (TCIE) — the year in which the average change in agricultural yield falls outside the historic range for a particular location. Jägermeyr explains: “The time of emergence [is]The year when mean changes are not within historical conditions. [and] we say OK, this is not normal anymore; this is the emergence of a signal that’s attributed to climate change.”

Using the period from 1983 to 2013 as a reference, the simulations confirm that in some subtropical regions, including the Middle East, Central Asia, parts of Mexico and the Western U.S., the TCIE has already occurred — climate change has already pushed agricultural productivity outside of the bounds of historical norms and into a new normal.

In the next decade, TCIE is expected to affect other major breadbasket regions in North America and Europe as well as Asia. “That’s alarming because it reduces the lead time for farmers, stakeholders, [and] policymakers, to really implement the adaptation pathways that are required,” Jägermeyr warned.

Inequality on the rise

The research team found that tropical regions — where corn is heavily cultivated and climate change will be most severe — can expect to see larger yield losses, felt sooner, than in temperate regions.

“In higher latitudes, where crop cultivation is often operating in temperature-limited regions … additional warming can actually be beneficial for crop growth,” due to fertile zone expansion and a lengthening growing season, Jägermeyr explained. In contrast, “smallholder regions in lower latitudes, where agriculture is often a self-sufficiency measure, will feel these impacts most directly, with the strongest implications for food security, livelihoods, and equality.”

These latitudinal variations in climate impacts could be exacerbated if there are physiological differences among crops. For example, higher atmospheric CO levels can be a benefit to wheat than corn.₂These levels can fuel crop growth. The study found that these combined factors will increase the burden of climate change in developing countries, which often have limited financing for climate adaptation.

Last month, vulnerable countries were represented at the COP26 summit on climate in Glasgow, Scotland. made a pleaInternational financial commitments should be made to adapt to global warming. While there is an adaptation pledge of “100 billion dollars annually from developed to developing countries was … reaffirmed,” at the summit, that promise, first made in 2009, has yet to be fulfilledBy high-income countries.

“There’s no question, [that] low-latitude farmers are at risk … in fact that’s a general truth about climate change,” said Robert Mendelsohn, a professor of economics at the Yale School of the Environment in Connecticut, USA, who was not involved in the study. He expressed concern for subsistence farmers, who “are among the most vulnerable,” to climate-driven food insecurity.

However, he added, “this [study]This reaffirms that the global is a reality. [food] supply is not at risk,” because losses in low latitudes will largely be alleviated by gains in high latitudes, and because farmers will hopefully adapt to changes in local climate.

Adapting to a changing climate reality

The study simulates changes to crop yields, assuming that farmers do not make any changes to their current farming methods. This is to isolate the effects of climate change. “This is critically important to understand and disentangle the complex climate change impact processes,” said Jägermeyr.

There are ways that farmers can minimize the loss of yield in tropical regions and maximize their gains in temperate zones. Some changes — such as sowing crops earlier or switching to heat-tolerant cultivars — are relatively inexpensive and simple to implement, while others, such as installing new irrigation systems, require financial investment, planning, and perhaps most importantly, time.

“In 74% of global corn-growing regions, we will see dramatic losses if we don’t act,” said Jägermeyr, concluding, “We need adaptation and we need it basically tomorrow.”

Mendelsohn is confident that farmers around the globe will adapt instinctively as the climate changes, as they have done so far, because “if they make those adjustments, they’ll earn more net revenue [so] the incentive is there already.”

Many climate crop adjustments won’t likely “require government intrusion; this is something individual farmers will do for their own sake,” he asserted. And taking those adaptations into account, “the [agricultural]These are just some of the possibilities. [model] predictions.”

Jägermeyr acknowledged that “some of these measures are being implemented by the farmers already in an inherent way, [with]One example [being] the shift in planting dates.” However, other adaptation measures, such as breeding new cultivars, switching crops, changing land-use patterns, and investing in irrigation, “are not as simple and need incentives and dedicated policy support in line with local realities,” he said.

Changes locked-in

Importantly, shifts of agricultural productivity in different regions around the world over the next decade are locked-in, according to the authors, because both the high-emission and low emission scenarios produced similar trends.

However, humanity’s actions can still have a profound impact on the actual severity of those long-term agricultural productivity trends, the research shows. According to the research, climate change mitigation actions can reduce corn yield losses by just 6% and maximize wheat productivity if taken now. “There are huge gains to be made, huge risks to be avoided, if we manage to steer away from a business-as-usual, high-emission pathway,” Jägermeyr said.

The study results “confirm the importance of changing the climate trajectory we are currently on if we want to maintain agricultural progress,” said David Lobell, Professor of Earth System Science and Director of Stanford University’s Center on Food Security and the Environment in California, who was not involved in the study.

Mendelsohn described the new simulations as “helpful,” because they demonstrate that “if the climate scenario looked like RCP8.5 — with gigantic emissions and therefore gigantic changes in temperature — that will have very big effects on yield.” However, he feels that the high-emission scenario often cited as ‘business-as-usual,’ is too pessimistic, requiring an increase in the rate of global economic growth to move us onto that disastrous pathway.

The research team is currently running additional crop simulations under a wider range climate scenarios to get a better picture. For the present study they chose “the most optimistic and the most pessimistic scenario available, to sample the range of potential climate change impacts,” Jägermeyr said.

What is clear in both modelled scenarios is that “agriculture is facing a new climate reality,” he warned. “In some parts [of the world] we need adaptation to exploit these gains, in other parts we need adaptation to avert negative changes, but the amount of change that’s coming is a lot and is surprising.”

“The spatial extent of these impacts are so widespread that deliberate adaptation measures, targeted, well-planned policies to implement adaptation, are critical and paramount,” Jägermeyr said.

Citation:

Jägermeyr, J., Müller, C., Ruane, A.C. et al. Climate impacts on global agriculture emerge earlier in new generation of climate and crop models. Nature Food 2, 873–885 (2021).

Banner image Corn is a staple crop across Africa and Latin America, and the world’s most popular grain. Subsistence farmers in subsistence areas of the global south face potential yield losses up to 24% by 2100, which could threaten their food security. Image courtesy: CIAT International Center for Tropical Agriculture on Visualhunt.

FEEDBACK: Use this formSend a message to the author by clicking here You can leave a public comment at the bottom.