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Climate change is shortening Central Asia’s growing season – study

Climate change is shortening Central Asia’s growing season – study

It’s bad news for plans to expand farming, but even worse for herders.

Climate change is rapidly shortening Central Asia's growing season, says a new analysis of vegetation data from the past two decades. Though the study looked at native grasses and trees rather than agricultural crops, the trend could dash hopes to expand farming and add to mounting concerns about food security.

The growing season – the time between the first shoots of fresh green in the spring and the withering of vegetation in the fall – has become longer in most of the middle latitudes of the northern hemisphere, as one might expect on our warming planet.

But the reverse is happening in most of Central Asia. Growth is starting later and ending earlier, even though Central Asia is warming faster than the global average, says a peer-reviewed study published this month in Science of the Total Environment.

Changing precipitation patterns may explain this seemingly counterintuitive trend. Vegetation is “more sensitive to precipitation” than to temperature, says the study. While most of Central Asia is becoming drier, which can shorten the season, instances of increased precipitation seem to have also ended the season earlier. While precipitation patterns are a more complicated variable than temperature, in both cases – wetter or drier – the implication is that the land will yield less food.

Lizhou Wu of the Nanjing University of Information Science and Technology in China and his coauthors start with temperature and precipitation data collected between the years 2000 and 2019. This they compare to the growth of native vegetation, measured both by satellite sensors and sampling points on the ground, in the same years. Then they break this giant region – the five Central Asian states plus large parts of western China – into six ecological zones, which they dissect by altitude in increments of 1,000 meters.