Posted on 09/02/2015 10:56:17 AM PDT by Red Badger
The global map of tree density at the square-kilometer pixel scale. Credit: Crowther, et al
A new Yale-led study estimates that there are more than 3 trillion trees on Earth, about seven and a half times more than some previous estimates. But the total number of trees has plummeted by roughly 46 percent since the start of human civilization, the study estimates.
Using a combination of satellite imagery, forest inventories, and supercomputer technologies, the international team of researchers was able to map tree populations worldwide at the square-kilometer level.
Their results, published in the journal Nature, provide the most comprehensive assessment of tree populations ever produced and offer new insights into a class of organism that helps shape most terrestrial biomes.
The new insights can improve the modeling of many large-scale systems, from carbon cycling and climate change models to the distribution of animal and plant species, say the researchers.
"Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution," said Thomas Crowther, a postdoctoral fellow at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study.
"They store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services," he added. "Yet you ask people to estimate, within an order of magnitude, how many trees there are and they don't know where to begin. I don't know what I would have guessed, but I was certainly surprised to find that we were talking about trillions."
The study was inspired by a request by Plant for the Planet, a global youth initiative that leads the United Nations Environment Programme's "Billion Tree Campaign." Two years ago the group approached Crowther asking for baseline estimates of tree numbers at regional and global scales so they could better evaluate the contribution of their efforts and set targets for future tree-planting initiatives.
At the time, the only global estimate was just over 400 billion trees worldwide, or about 61 trees for every person on Earth. That prediction was generated using satellite imagery and estimates of forest area, but did not incorporate any information from the ground.
The new study used a combination of approaches to reveal that there are 3.04 trillion trees—roughly 422 trees per person.
Crowther and his colleagues collected tree density information from more than 400,000 forest plots around the world. This included information from several national forest inventories and peer-reviewed studies, each of which included tree counts that had been verified at the ground level. Using satellite imagery, they were then able to assess how the number of trees in each of those plots is related to local characteristics such as climate, topography, vegetation, soil condition, and human impacts.
"The diverse array of data available today allowed us to build predictive models to estimate the number of trees at each location around the globe," said Yale postdoctoral student Henry Glick, second author of the study.
The resulting map has the potential to inform scientists about the structure of forest ecosystems in different regions, and it can be used to improve predictions about carbon storage and biodiversity around the world.
"Most global environmental data is thematically coarse," said Matthew Hansen, a global forestry expert from the University of Maryland who was not involved in the study. "The study of Crowther et al. moves us towards a needed direct quantification of tree distributions, information ready to be used by a host of downstream science investigations."
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 percent of the world's trees. (Only 24 percent are in the dense boreal regions, while another 22 percent exist in temperate zones.)
The results illustrate how tree density changes within forest types. 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.
In fact, human activity is the largest driver of tree numbers worldwide, said Crowther. While the negative impact of human activity on natural ecosystems is clearly visible in small areas, the study provides 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.
"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," Crowther said. "This study highlights how much more effort is needed if we are to restore healthy forests worldwide."
Researchers from 15 countries collaborated on the study.
More information: Nature, DOI: 10.1038/nature14967
Journal reference: Nature
Me too...............
http://www.livescience.com/7725-lost-forests-america.html
“Around the arrival of Columbus, “it’s said that squirrels could travel from tree to tree from the Northeast to the Mississippi without ever having to touch the ground,” said Chris Roddick, chief arborist at the Brooklyn Botanic Garden in New York. “In the old growth forests in the Northeast, you had hemlock that were six or seven feet in diameter, chestnut trees 200 feet tall.”
Of course if your name was Rocket J. Squirrel, you didn’t need any stinking trees.
We need to stop using wood. It is apparently a limited resource now.
If only we could get trees to grow on the moon. We might have a place to send these lunatics.
Funny. Using Google World, or whatever it's called, I counted only 2,999,999,874,299.
My bad, I just cut one down last week................
They were 750% off on their earlier estimates yet they know that there are 46% less than before humans lived.
The others...fruit trees.
A new Yale-led study estimates that there are more than 3 trillion trees on Earth, about seven and a half times more than some previous estimates. But the total number of trees has plummeted by roughly 46 percent since the start of human civilization, the study estimates.Ivy covered brain ping -- the Romans cleared out the forests, beginning with the areas adjacent to their roads, and over centuries nearly denuded Britain, Gaul, etc. During the Middle Ages, basically by a century or so after Roman occupation ended, the forests were back.
Well, if we can just find some aliens that will pay us $6/tree for the logging rights, we could pay off the national debt :)
It is the fault of that Save-the-Trees movement from several decades ago.
Trees converted to lumber no longer produce CO2.
Living trees absorb CO2. Rotting trees produce CO2 (decay). But you knew that.
There’s a tree here we call a ‘Popcorn Tree’. It grows like crazy in even the poorest soils. It is an invasive species, and will displace native trees. Its seeds are poisonous to animals. These trees are truly evil..................
Only certain trees produce CO2 and only in limited circumstances. The majority of the time, they are a CO2 sink, absorbing it from the atmosphere to photosynthesize into sugars.
They compared it to satellite photos from 1000bce.
Even so, its all pretty academic. The old green mantra of "the amazon rain forest is the lungs of the planet" is nonsense. The amount of CO2 absorbed by trees is a fraction of what is taken in by phytoplankton in the oceans.
LOL...good point!
watch this number fail to be reflected in any “climate change” model
heh heh heh...very good!
Lies. The world is far more forested than say 5000 years ago. This propaganda.
Q—Do trees give off Carbon Dioxide?
A—At night they do. During the day, they give off oxygen.
All normal plants, in the process of photosynthesis, take up carbon dioxide by day and release oxygen. This switches over in the dark, and they then produce carbon dioxide through respiration in the same way as animals. While they are growing, they take up more carbon dioxide overall than they give out, which gets turned into plant tissues (especially cellulose and, in the case of trees, lignin).
http://www.answers.com/Q/Do_trees_give_off_Carbon_Dioxide
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