Video Transcript

Narration: Erica Drezek


[NARRATOR] Since instrumental measurements began in the 1880s, the past decade is officially the warmest on record. Previous research suggested that in the 80s and 90s, warmer temperatures and higher levels of precipitation – factors associated with climate change - were generally good for plant growth. But it is possible we had too much of a good thing. An updated analysis published this week in the journal Science indicates that as temperatures have continued to rise, the benefits to plant growth are now overwhelmed by longer and more frequent droughts. Scientists from the University of Montana investigated global Net Primary Production of land plants using satellite data from the past three decades. An instrument on NASA’s Terra satellite provides insight as to whether plants are actually benefitting from a changing climate. High resolution data from the Moderate Resolution Imaging Spectroradiometer, or MODIS, indicate a net decrease in primary production from 2000 through 2009, as compared to the previous two decades. Primary production is a measure of plant growth and the first step in the carbon cycle. Carbon enters the atmosphere from a variety of sources including deforestation, fossil fuel burning, and wildfires. Plants absorb carbon from the atmosphere and use it to grow; as they continue to grow, they pull down more carbon and slow the increasing concentration of carbon dioxide in the air. It is important for scientists to monitor changes of primary production, as changes in plant growth affect the balance of carbon between the atmosphere and terrestrial ecosystems . This visualization represents the amount of carbon that was removed from the atmosphere by plants during the warmest decade on record. An increase in primary production, as indicated in green, tells us that plants are removing carbon dioxide faster than they usually do… …while a decrease in primary production, in red, means that carbon dioxide is being removed more slowly from the atmosphere by plants. Higher temperatures led to longer growing seasons, and increased amounts of water and sunlight in the Northern Hemisphere, causing a net increase in atmospheric primary production. But it was not enough to offset the decrease in carbon absorption in the southern hemisphere, leading to more carbon dioxide in the atmosphere. Africa, for instance, suffered a severe drought in 2005. Crops suffered major losses, and with less green vegetation to fix the carbon, there was more of it left in the atmosphere. The planet as a whole experienced a net decrease in primary production over the past ten years, but it was a modest decrease. This research reinforces the idea that climate variability is complex. With increasing demands on our natural resources, a growing population and expansion of biofuel production, it is critical to monitor the large-scale changes in plant growth and how it affects carbon levels.