How many trees do humans cut down a year


Global forest survey finds trillions of trees

Global forest survey finds trillions of trees

Download PDF

Download PDF

  • Published:
  • Rachel Ehrenberg 

Nature (2015)Cite this article

  • 19k Accesses

  • 4 Citations

  • 1394 Altmetric

  • Metrics details

Subjects

  • Ecology
  • Environmental sciences

Combination approach uses ground-based surveys and satellites to find many more trees than anticipated.

There are roughly 3 trillion trees on Earth — more than seven times the number previously estimated — according to a new tally by an international team of scientists. The study also finds that human activity negatively affects tree abundance from the boreal forests to the equator. Roughly 15 billion trees are cut down each year, the researchers estimate; since the onset of human civilization, the global number of trees has dropped by roughly 46%.

“The scale of human impact is astonishing,” says Thomas Crowther, an ecologist at the Netherlands Institute of Ecology in Wageningen who led the study while at Yale University in New Haven, Connecticut. “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.”

The widely accepted previous estimate of the world’s tree population, about 400 billion, was based largely on satellite imagery. Though remote imaging reveals a lot about where forests are, it does not provide the resolution of a person counting trunks in a particular plot. Crowther and his colleagues merged these approaches by first gathering data from more than 400,000 ground-based counts reported in forestry inventories and the scientific literature for every continent except Antarctica. These counts allowed them to improve tree-density estimates based on satellite imagery. Then the researchers applied those density estimates areas that lack good ground inventories. For example, ground-truthed data from forests in Canada and northern Europe were used to revise estimates from satellite imagery for similar forests in remote parts of Russia.

“It’s not like we discovered new trees,” says Crowther. “Rather, we added another layer of information that allowed us to revise much of the previous estimates.”

Improved population estimates could help managers weigh the economic benefits that forests provide in terms of water purification, soil conservation and other functions against those of harvesting timber or clearing trees for farmland, says ecosystems services ecologist Becky Chaplin-Kramer of Stanford University in California. “It’s great when we can fill in gaps like this,” she says.

The highest tree densities, calculated in stems per hectare, were found in the boreal forests of North America, Scandinavia and Russia. These forests are typically tightly packed with skinny conifers and house roughly 749.34 billion trees, 24.28% of the global total. Tropical and subtropical forests, with the greatest area of forested land, are home to 1.29 trillion trees, or 42.82% of the total.

The new numbers raise questions about which species are represented where and how particular forest types evolve, says biogeochemist Susan Trumbore of the Max Planck Institute for Biogeochemistry in Jena, Germany.

The number of trees is just one piece of the puzzle,” Trumbore says. “A tree in the tundra is not the same as a tree in the rainforest.”

Crowther cautions that even though the new figures do not change the current science on carbon storage or diminish the impact of deforestation. “We’re not saying, ‘Oh, everything’s fine’.

In fact, the work suggests that in some places where one might expect trees to thrive, such as warm regions with lots of moisture, human activities like farming have pushed forest to the margins.

Authors

  1. Rachel Ehrenberg

    View author publications

    You can also search for this author in PubMed Google Scholar

Related links

Related links

Related links in Nature Research

Stopping deforestation: Battle for the Amazon 2015-Apr-01

Tropical forest losses outpace UN estimates 2015-Feb-26

Fibre production drives deforestation in Indonesia 2014-Jul-21

Related external links

Rights and permissions

Reprints and Permissions

About this article

This article is cited by

  • Impacts of oak deforestation and rainfed cultivation on soil redistribution processes across hillslopes using 137Cs techniques

    • Shamsollah Ayoubi
    • Nafiseh Sadeghi
    • Jesus Rodrigo-Comino

    Forest Ecosystems (2021)

Download PDF

How many trees are cut down every year?

  • A new study published in Nature estimates the planet has 3. 04 trillion trees.
  • The research says 15.3 billion trees are chopped down every year.
  • It also estimates that 46% of the world’s trees have been cleared over the past 12,000 years.

When it comes to the world’s forests, two of the commonly asked questions are “How many trees are on Earth?” and “How many trees are cut down each year?” A new study proposes answers: three trillion and 15.3 billion.

The research, published today in the journal Nature, is based on a combination of satellite imagery, on-the-ground inventories, and computer modeling led by Thomas Crowther of the Netherlands Institute of Ecology. Crowther conducted the research while at Yale University.

“Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution,” Crowther was quoted as saying in an article posted on Yale’s web site.

Hear this article being read aloud here via Mongabay’s podcast:

Pittsfield State Forest in Massachusetts. Photo by Rhett A. Butler.

“They store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services. 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.”

Three trillion trees is far higher than the previous leading estimate of 400 billion trees. The wide discrepancy is the result of the more comprehensive methodology used by the research team.

“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.

Image highlighting the ecoregions (shapefiles provided by The Nature Conservancy) from which the 429,775 ground-sourced measurements of tree density were collected. Shading indicates the total number of plot measurements collected in each ecoregion. A global forest map was overlaid in green to highlight that collected data span the majority of forest ecosystems on a global scale. b, The median and interquartile range of tree density values collected in the forested areas of each biome. Image and caption courtesy of Nature.

The research broke down tree cover by biome and country, finding the highest density in boreal forests, which altogether house 750 billion trees, or about a quarter of the world’s total. The largest extent of forests exist in the tropics, which have 1.3 trillion trees, or 43 percent of the planet’s trees. The differences make intuitive sense given the high diversity and larger size of trees in the tropics versus sub-arctic regions.

By country, Russia had the most trees at 642-698 billion. It was followed by Canada (318-361 billion trees), Brazil (302-338 billion), the United States (222-228 billion), and China (140-178 billion). The highest density among countries with significant amounts of forest cover was Finland, with more than 72,000 trees per square kilometer. It was followed by Slovenia, Sweden, and Taiwan.

Redwood forest in Muir Woods, California. Photo Rhett A. Butler.Temperate rainforest on Washington’s Olympic Peninsula. Photo by Rhett A. ButlerTemperate forest in New Hampshire. Photo by Rhett A. Butler

The study also estimated current and historical rates of tree cover loss. It said that the number of trees worldwide has fallen 46 percent since the dawn of agriculture 12,000 years ago and more than 15 billion trees are felled every year.

That loss has significant implications for the planet in terms of climate change, biodiversity, and human well-being, according to Crowther.

“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,” he said. “This study highlights how much more effort is needed if we are to restore healthy forests worldwide.

Rainforest in Sabah, Malaysia. Photo by Rhett A. Butler.

CITATION: T. W. Crowther et al (2015). Mapping tree density at a global scale. Nature dooi:10.1038/nature14967 Published online 02 September 2015

These questions can help provide a framework for exploring topics presented in this story.

  • Why are trees important?
  • What forests have the highest density of trees?
  • What country has the most trees?
  • How has the number of trees in the world changed over time?
  • What percentage of trees have been lost?

Test your knowledge.

Archive, boreal forests, Deforestation, Environment, Forests, learning resources, Rainforests, Satellite Imagery, Temperate Forests, Tropical Forests

Print

Trees on Earth are 8 times more than previously thought

Subscribe to our newsletter "Context": it will help you understand the events.

Image copyright Reuters

Image caption

New data show there are eight times as many trees on the planet as previously claimed

There are about three trillion trees on the planet, according to Yale scientists. This data, collected using satellite imagery and forestry data, is eight times higher than previous figures, when it was reported that there were about 400 billion trees growing on Earth.

Estimates were made on more than 400 thousand sites on all continents.

According to research team leader Dr. Thomas Crowther, there are now about 420 trees for every inhabitant of the Earth.

As noted in a report published in the journal Nature, these studies will help to elucidate other important factors in the life of the planet - from the biological diversity of the animal world, to the modeling of climate change, which are significantly affected by the absence or presence of large forests that absorb huge amounts of greenhouse gases. gases, converting them into oxygen.

In an interview with the BBC, Dr. Crowther, however, notes that the data from this study do not indicate that the state of the planet, the atmosphere, the level of carbon dioxide turned out to be "good" or "bad", it is simply data about , what is the current state of these forest areas.

"We simply described the state of the planet's forest system, so that the data could then be used, for example, by environmentalists for their research, or politicians and governments for their own purposes," says Dr. Crowther.

According to scientists, the largest number of trees - about two trillion - grow in the tropical and subtropical zones of the planet, which is quite natural.

Image copyright, Reuters

Photo caption,

Researchers believe the data will help understand the causes of climate change on the planet and how threatening the consequences are

Skip Podcast and continue reading.

Podcast

What was that?

We quickly, simply and clearly explain what happened, why it's important and what's next.

episodes

The End of the Story Podcast

In addition, this study provides a clear picture of human impact on vegetation on earth. According to the data received, about 15 billion trees (or 0.5% of the total) are cut down on the planet every year, while no more than five billion are planted.

"Now we can see how fast the planet is being deforested. Combined with other data like climate change, we can understand how deforestation affects the climate," says co-researcher Dr. Henry Glick.

This study also allows us to compare the current state of forests with what it was, for example, after the end of the Ice Age. Scientists say that since then, humanity has cut down almost three trillion trees on the planet.

"Europe was almost completely covered with forest, and now it is almost continuous fields and meadows. And it is, of course, human activity that has led to such results," says Dr. Crowther in an interview.

At the same time, other scientists doubt the accuracy of this study. Dr. Martin Lucas of the University of Reading in England says that the inaccuracies of recent studies, when they counted only 400 billion trees on Earth, suggest that this study, which increased the number of trees by eight times, may eventually turn out to be inaccurate.

Other scholars also point out that this study was meticulously carried out only in Europe and North America, and regions such as India, Australia, China and the Congo were practically not studied. Therefore, the following data can again increase the number of trees by two, and maybe 10 times.

Historically, fewer trees are cut down in Russia than in the USA and Europe

Why Russia has the most trees in the world, how to deal with deforestation and how many trees have been destroyed by people throughout the history of mankind, says the science department of Gazeta.Ru.

Leading author Thomas Krauser, Yale University professor, told Gazeta.Ru about the large-scale study that resulted in the world's forest density map and publication of article in the prestigious Nature magazine.

“The main thing is to know the height of the flame”

How forest fires are extinguished in Russia and abroad, why water does not help to effectively and quickly put out. ..

August 27 18:20

— Thomas, how are the forests on our planet?

- Various. Initially, my colleagues and I set ourselves the goal of creating the world's first forest density map. A map like this has helped us gain a more fundamental understanding of what is happening to the Earth, allowing us to predict the future of many species and understand what is happening with carbon sequestration and storage in forests.

And this map also made us understand how many trees there are in the world. And there are about 3.04 trillion of them.

At the same time, there are 15 billion more trees every year. But the rate of reduction of forest tracts is also high - about 10 billion disappear every year. And since the appearance of man, about 46% of the forest tracts that covered the Earth's surface have disappeared.

— What are the main causes of deforestation on our planet?

- Initially, the main reason for the disappearance of forests was that people began to engage in agriculture and began to adapt the land for this business. Then industrialization began, and now urbanization is actively going on.

The higher the rate of human activity, the faster the trees disappear. This is an exact rule.

— Which forests are most endangered?

— Most trees are cut down in the tropics. There are almost no virgin forests left on the planet.

The consequences of this can already be seen in northern latitudes.

Regions that historically had the highest rates of production and advanced agriculture saw the fastest deforestation. So, Europe was originally covered with one giant forest, but for several centuries, little has remained of this forest thanks to people.

Anniversary of the heat wave

Exactly five years ago, a period of abnormal heat began in Moscow and Central Russia: from July 14 to August 15...

July 14 09:49

— What is the situation with forests in Russia?

— Russia has more trees than any other country in the world. So, there are twice as many of them as in Canada, which is in second place after Russia in this indicator.

Compared to other forests, historically less forests have been cut down in Russia than in Western Europe and North America. In general, given the scale of Russian forests, it should be noted that they make up a significant part of the global number of forests.

There are also regularities - the closer Russian forests are to city limits, the faster they disappear.

— How can we improve the situation with forests on the scale of Russia and the world?

- The only way to change something is to start gardening. In the long term, this will help not only restore forests destroyed by man, but also somehow compensate for the damage caused by man through new forests. And this will help us not to lose biodiversity in these areas and improve the situation with carbon sequestration and storage.

But that will take a very long time.

close

100%

— How was the map made?

- We collected data from all over the world, involving scientists who counted the number of trees and forests in their countries. In particular, we were able to obtain information about 429,577 places around the world, as well as understand what is the density of forests in individual countries and around the world. We also used satellite images, which allowed us to clarify the data from scientists.

And this allowed us to develop certain methods. So, knowing that there are always more trees in humid places, we were able to calculate the approximate number of trees in certain areas using the humidity indicator.

We can now make fairly accurate calculations based on the available data and satellite imagery. And this is very useful, because we will definitely not bypass all the forests of the world.

“In Russia, about 45 million hectares of arable land are abandoned”

How can Russia and its neighbors ensure productivity, not remain hungry and effectively use the once ...

June 30 13:08

— Did Russian researchers help you in your work?

— Since vast areas are covered with forests in Russia, we really wanted to get information about the density of Russian forests.


Learn more