American trees die faster because of climate

The number of trees in ancient forests throughout the western states of the United States is decreasing with increasing proportions. Scientists say this phenomenon is caused by the longer and hotter summers stemming from climate change.

For those who walk in the forest it is almost impossible to recognize the change, but in fact every three decades the number of dead trees in the United States doubles. This is the result of a study of data for a new 52-year period published last weekend. This fast-growing dead tree trend occurs in trees of all ages, species and locations.

Research leader Phillip J. van Mantgem of the US Center for Ecology said: ' If this trend continues, forests will become more sparse leading to a decline in the size of the tree. This is important because it is a sign that in the future the forests will only absorb less carbon than they currently '.

Professor Jerry Franklin (University of Washington) said that ancient forests in the northwestern United States absorb large amounts of carbon and play an important role in fighting global warming. But when plants die they emit carbon dioxide and further increase greenhouse gas emissions. Meanwhile, young forests absorb very little carbon and it takes hundreds of years to replace old forests.

Fall scene near a village in Northville, Michigan.(Photo: AP)

In addition to the phenomenon of climate change, the researchers also considered a number of other causes that increase the number of dead forest trees such as air pollution, the number of young trees is too large, the consequences of felling trees or Big tree pressing baby tree. But the collected data led the researchers to conclude that the average warming temperature is the fundamental cause of the phenomenon. Climate change causes plants to be severely dehydrated, leading to vulnerability to pests.

The study, funded by the US Geological Survey, examined data from 1955 to 2007 at 76 different points, in the areas of British Columbia, Washington, Oregon, California, Idaho, Colorado. and Arizona. The forests studied have an average age of 450 years, some of which are thousands of years old. Of the 59,736 trees recorded, 11,095 were killed during the study. The rate of dead plants increased most rapidly in Sierras in California (the rate of dead trees in 1980 was 0.9% increased to 1.3% in recent years).