Posted by News Express | 19 September 2015 | 3,541 times
A study by an international team of researchers said that there are 3.04 trillion trees on Earth, roughly 422 trees per person and the number is about seven times greater than previous estimates.
The published study the journal Nature, noted that the number of trees has dropped by 46 per cent, almost half since the onset of agriculture about 12,000 years ago.
Thomas Crowther, a Yale University Climate & Energy Institute postdoctoral fellow, the lead author of the study, said trees store huge amounts of carbon, which are essential for the cycling of nutrients, for water and air quality, and for countless human services.
He said with the use of combination of satellite imagery, forest inventories, and supercomputer technologies, the researchers were able to produce a global map of tree density at the square-kilometer pixel scale.
Crowther said the highest densities of trees were found in the boreal forests in the sub-arctic regions of Russia, Scandinavia, and North America.
“But the largest forest areas, by far, are in the tropics, which are home to about 43 per cent of the world’s trees.
“Only 24 per cent are in the dense boreal regions, while another 22 per cent exist in temperate zones.
“Around 15 billion trees are cut down each year; in fact, human activity is the largest driver of tree numbers worldwide.
“The scale of human impact is astonishing, and obviously we expected humans would have a prominent role, but I didn’t expect that it would come out as the as the strongest control on tree density.”
Crowther said the researchers found that climate can help predict tree density in most biomes.
“In wetter areas, for instance, more trees are able to grow.
“However, the positive effects of moisture were reversed in some regions because humans typically prefer the moist, productive areas for agriculture.”
He said while the negative impact of human activity on natural ecosystems is clearly visible in small areas, the study provided a new measure of the scale of anthropogenic effects, highlighting how historical land use decisions have shaped natural ecosystems on a global scale.
“In short, tree densities usually plummet as the human population increases.
“Deforestation, land-use change, and forest management are responsible for a gross loss of over 15 billion trees each year.”
Crowther said we’ve nearly halved the number of trees on the planet, and we’ve seen the impacts on climate and human health as a result. (PANA/NAN)
•Photo shows Trees
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