Photo jcookfisher @ flickr.
Global warming may be the culprit in the waves of tree deaths scientists have observed in the western U.S. in unmanaged, old-growth forests, reported in the latest issue of Science. Tree death rates have doubled in these old-growth forests since the 1950s, and the U.S. Geological Survey, leading the study, speculates that rising temperature and its results is the most likely culprit (fire suppression and a few other factors were mostly ruled out). These decimated forests could eventually become net carbon dioxide producers, rather than currently helping us suck CO2 from the atmosphere.Trees get stressed, too
Western forests studied have experienced approximately a half-degree (Celsius) increase in temperatures for each decade during the last few decades the USGS scientists studied. "Mortality rates are increasing...and the likely driver is widespread increasing temperature," Phillip van Mantgem, lead researcher, told Science Podcast.
The death rates were seen in different types of forests, in trees of all sizes and among different species. The scientists suspect that trees are dying from the stress of less snow melt, longer droughts, and more pests such as bark beetles and fungi - all of these a result of higher temperatures. The highest mortality - a rate of 1.5% annually - was in California, reports the Los Angeles Times.
Where's the Lorax when needed?
Unfortunately, the stands studied are relatively undisturbed forested areas usually more than 200 years old. Some forest experts believe that if mortality is very high in these unmanaged forest stands, it is worse in the managed regions where fire suppression has been used. van Mantgem recommended that foresters try to remove exotic species from these forest areas but with abrupt changes that global warming may have in store, the old model of "restore historic conditions" might be pretty hard to follow. "It's a challenging time to be a forest manager,"he told Science Podcast. Via: Science, LA Times
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