Climate Change Shortens Growing Seasons

As human populations swell and require more food, climate change will likely create a planet that produces less and less.
By Kate Wheeling,
Climate change effects in the island nation of Kiribati. (Photo: United Nations Photo/Flickr)

Ecologist Camilo Mora knows how climate change can negatively impact farming. "Here in the third world is where you can really see the consequences of the land losing the capacity to produce food," Mora says, speaking from a farm in El Bolo, a rural community in Colombia, where he grew up and still spends his summers. So Mora, an assistant professor at the University of Hawai’i-Mānoa, was skeptical when a climate denier mentioned research that indicated rising temperatures could give plants in the cool regions at high latitudes more time to grow. Until, that is, Mora looked up the research for himself.

"[It was] hard to admit, but this person was right," Mora says. But Mora, a former farmer himself, knew that temperature was just one factor, and those surprising research findings couldn't be the whole story. To get a full picture, Mora and his colleagues carried out research that considered the effects of climate change on soil moisture, as well as the amount of solar radiation.

There could be an 11-percent drop in the length of growing seasons worldwide by 2100.

In a study published today in PLoS Biology, the team reports that while a few high-latitude countries may indeed see some positive outcomes as the climate warms, globally, the prognosis is poor. Even with high-latitude gains, there could be an 11-percent drop in the length of growing seasons worldwide by 2100.

The researchers identified the range of temperatures, water supply, and sunlight under which plants grow around the globe. They then calculated the number of days per year that would fall within these thresholds of suitable growing conditions under three climate change projections—one in which strong carbon emission mitigation strategies are adopted, another with moderate mitigation strategies, and a "business-as-usual" scenario in which emissions continue at the current rate through the end of the 21st century.

"The only places that appear to benefit considerably from climate change will be Canada, Russia, and China," Mora says. But overall, any gains those high-latitude countries see due to rising temperatures would be offset by issues such as drought at lower latitudes. In the worst case, the "business-as-usual" scenario, by the end of the century, the tropics could lose as many as 200 growing days per year, the researchers found.

These issues will only become more pressing as the population grows to nine billion or more by the year 2100, according to Mora. "Right now there are one billion people going hungry," he says. "You can imagine what it would be in 2050 or 2100 if we add two billion more people to the planet."

But not every climate scenario the researchers observed resulted in our grandchildren living out Mad Max. The effects of climate change on growing seasons in scenarios with strong and moderate emission mitigation strategies were much less severe. And with this week’s declaration from the G7 summit for a global phase out of fossil fuels over the next century, there are still reasons to be optimistic about the future.

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