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Earth’s trees number three trillion

Manzurul Alam Mukul || risingbd.com

Published: 05:33, 3 September 2015   Update: 15:18, 26 July 2020
Earth’s trees number three trillion

Risingbd Desk: There are just over three trillion trees on Earth, according to a new assessment.


The figure is eight times as big as the previous best estimate, which counted perhaps 400 billion at most.


It has been produced by Thomas Crowther from Yale University, and colleagues, who combined a mass of ground survey data with satellite pictures.


The team tells the journal Nature that the new total represents upwards of 420 trees for every person on the planet.


Indeed, it is in the boreal forests that they say the greatest densities are seen.


What is abundantly clear from the study is the influence humans now have on the number of trees on Earth. The team estimates we are removing about 15 billion a year, with perhaps only five billion being planted back.


"The net loss is about a third of a percent of the current number of trees globally," said co-author Dr Henry Glick.


"That doesn`t seem to be an insignificant portion and should probably give us cause for considering the role that deforestation is playing in changing ecosystems.


"And where tree losses are often tied to timber supplies and land-use conversion for agriculture, as the global human population grows, we may see the net loss increase as well."


And as if to emphasise this point, a comparison with estimates of ancient forest cover suggests that humanity could have already removed almost three trillion trees since the last ice age, some 11,000 years ago.


"Europe used to be almost covered by one giant forest and now it`s almost entirely fields and grasslands. Humans are absolutely controlling tree densities," Dr Crowther told BBC News.


Commenting, Dr Nathalie Pettorelli from the Zoological Society of London said the study was unlikely be the last effort to do a global tree count.


She told the UK Science Media Centre: "It may be important to acknowledge that these first estimates produced by Crowther and colleagues are derived from data primarily collected in Europe and North America, with [for example] very little information collected in the Congo basin, China, Australia or India.


"As more information becomes available for these countries, it might be interesting to refine the estimates and check that key processes shaping spatial variability in tree density have not been overlooked."


And Dr Martin Lukac from the University of Reading was still not sure we were near an accurate count.


"The previous estimate of trees in the world was 400 billion. The new estimate is three trillion large trees. There are so many margins of error in this study that the real number could be anything between the two - or even 10 times higher," he said.


Source: BBC online


Risingbd/Sept 3, 2015/mukul

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