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Variation in rainfall patterns to take a toll on key crops by 2040

Projections show parts of Europe, Africa, the Americas and Australia will be drier, while the tropics and north will be wetter
by TR Pakistan

Drastic changes to rainfall patterns are set to take a toll on yields of four crops that account for 40 percent of global caloric intake, says a new study.

The study has found that up to 14 percent of land dedicated to wheat, maize, rice and soybean will become drier, while up to 31 percent will get wetter by 2040, even if the greenhouse gas emission targets set by the Paris Agreement are met.

Researchers have used four emissions scenarios from low to high to predict time of emergence (TOE) of permanent precipitation changes, which means the year by which precipitation changes will remain permanently outside their historical variation in a specific location in the world.

They have found that wetter areas include Canada, Russia, China, India and the Eastern United States while drier regions include Southwestern Australia, Southern Africa, southwestern South America, and the Mediterranean. According to the study, wheat cropland in Central Mexico can also expect a drier future.

Many major wheat producers such as Australia, Algeria, Morocco, Chile, Spain, Mexico, Italy, Egypt, Turkey and South Africa will be affected and can expect less precipitation under a scenario where there are mid-emissions of greenhouse gases. According to the study, higher emissions will mean a larger amount of land will become dry sooner.

“These are definitely countries that will need to think rather quickly what they’d like to do with their wheat production,” said Maisa Rojas, the study’s lead author and climatologist at Universidad de Chile, in a statement.

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“What we’re predicting are probably conservative years for time of emergence. Detectable precipitation changes are of course not only important for agriculture, but for water resource management more in general, so our results are relevant for other sectors as well,” she added.

This infographic shows a selection of areas and crops that will be affected by reduced rainfall in coming decades due to climate change, according to a 2019 study in PNAS. Percentages refer to area of land currently dedicated to cultivation of the specified crops. Credit: Lucelly Anaconas / CIAT

The study also emphasized how quickly global precipitation is changing. The baseline used for comparison is 20 years spanning 1986-2005 and a number of regions already have crossed that “historical” average into an entirely new rainfall regime, including Russia, Norway, Canada and the parts of the East Coast of the United States. Under a high-emission scenario, the study projects that up to 36 percent of all land area will be wetter or drier.

“Farmers growing crops in those areas are going to experience significantly different conditions than what they are used to,” said Julian Ramirez-Villegas, a scientist with the International Center for Tropical Agriculture (CIAT) and the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).

China and India, which are the world’s most populous countries, are among those that will have much wetter fields for the four crops included in the study, under any emission scenario.

The researchers said that more precipitation may mean higher production, but when coupled with rising sea levels, higher temperatures and increased potential for flooding, higher production is not assured.

Co-author of the study Fabrice Lambert said, “The interesting thing about this study is that we overlay the climatic results with spatial cropland distribution and growing seasons to show which agricultural production regions will be impacted by precipitation changes, and how much time they have to prepare.”

“The precise nature of the changes is impossible to predict,” said Andy Challinor, a co-author and Professor at the University of Leeds. “What this study tells us is that adaptation needs to be agile. For the first time, we can tell what changes to be ready for – and when they are expected – in our major crop-growing regions. Prior to this study, the rainfall changes experienced by crops were thought to be so unpredictable that no real advice could be given.”

If quick action on emissions, in accordance with the Paris Agreement, are taken then it would reduce the size of affected areas or give more time for TOE projections to take place. The study notes that regardless of how much mitigation is achieved, all regions need to invest in adaptation, especially in areas that are expected to see major changes in the next couple of decades.

Low-emission scenarios imply less need for potentially costly adaptation to new precipitation regimes. However, in the scenarios with low greenhouse gas emissions, most regions have two-three decades more to adapt than under high-emission scenarios.