NASA scientists studying two decades of agricultural activity have found that global warming may not be as beneficial to crops as first thought.
Following sustained increases in yield during the 1980’s and 1990’s, it was widely believed that the temperature increases which coincided with the period were partly responsible due to longer growing seasons and milder winters. A 6% growth in agricultural productivity between 1982 and 1999 was seen as evidence that the planet could benefit from global warming.
In fact, by studying a number of variables – solar radiation, temperature and water availability in different geographic locations, NASA’s researchers were able to establish how different factors limited crop yields in different locations. In latitudes north of the equator, temperature was frequently the single most important factor in successful agriculture. However in more southern latitudes water availability was more commonly the problem. This meant that while the initial effects recorded for increasing temperatures created a net gain in crop outputs worldwide, warming began to work against growers in the south who saw more instances of drought.
NASA used their Terra satellite to read CO2 levels attributable to crop density and behavior.
The net effect, they found, was a global reduction in land productivity between 2000 and 2009.
This raises concerns not only for future food production (in conjunction with rapid population growth) but also for the role of plants as users of carbon dioxide, a key gas that contributes to global warming. Failing crops reduced the amount of Carbon Dioxide that is removed from the Earth’s atmosphere, contributing further to the rising temperatures.
Watch this video from NASA’s Earth Science Media for more detail and an outline of the carbon cycle.