Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Earth Has Lost Half of Its Trees Since Dawn of Civilization

Science
Earth Has Lost Half of Its Trees Since Dawn of Civilization

An international collaboration of scientists has just completed the ultimate green census—by calculating that the planet is home to 3.04 trillion trees. The latest estimate is far higher and almost certainly more accurate than any previous attempt. But the bad news is that humans are removing trees at the rate of 15 billion a year—and there are now about half as many as there were at the dawn of civilization.

Global map of tree density. Image credot: T Crowther et al

For every person on Earth, there are 422 trees—in total, more than 3,000 billion deciduous or evergreen growths with woody trunks greater than 10 centimeters at breast height. The researchers based their study on close analysis of satellite imagery, and of data from 429,775 plots of trees as measured on the ground in 50 countries on every continent except Antarctica. Statistical Techniques They counted forests in 14 “biomes”—or different kinds of climate, soil and topography—and in places not normally associated with trees, such as deserts, savannah, swamps, tundra and high mountains. They then they used statistical techniques that could extend their sample density measurements to the whole terrestrial world. The scientists report in Nature journal that the tropical and subtropical forests are home to 1.39 trillion trees, while the boreal forests of the north contain 0.74 trillion, and the temperate zones hold 0.61 trillion. Trees create and hold soil, forests become “sponges” that conserve and recycle water, and trees and forests between them sustain most terrestrial life, and provide human societies with food, medicines, building materials and even fabrics. They also play a vital role in the management of the atmosphere, as absorbers of carbon dioxide. So an accurate “fix” on the numbers and density of forest landscapes becomes a first step in climate modeling, and in planning for the conservation of biodiversity. “Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution,” says Thomas Crowther, an ecologist at the Yale School of Forestry and Environmental Studies 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. “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.” Read page 1 The study grew out of the United Nations Environment Programme’s Billion Tree Campaign, launched in 2006. Previous global estimates of tree populations were based on satellite imagery, and the best guess had been that the total was just over 400 billion trees, or 61 per person. This widely-accepted figure began to look uncertain as soon as researchers took a closer look at measurements made in one great tropical forest, which suggested there might be 390 billion trees in the Amazon basin alone. The international team found that the greatest densities of trees were in the sub-Arctic forests of Russia, Scandinavia and North America, which hold 24 percent of the world’s woodland. The largest forest areas were in the tropics, which are home to about 43 percent of the world’s trees. The temperate zones contain 22 percent of all trees.

Sub-Arctic forests in regions such as Scandinavia hold almost a quarter of the world’s woodland. Photo credit: Per Ola Wiberg via Wikimedia Commons

But although the total surprised researchers, the fact remains that the tree cover has fallen by 46 percent since the end of the last Ice Age. As human populations have grown, more and more forests have been cleared, and humans now fell or burn 15 billion trees a 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,” Dr Crowther says. “This study highlights how much more effort is needed if we are to restore healthy forests worldwide.” Scientists welcomed the study—although there were some reservations. Helen McKay, who heads the Centre for Sustainable Forestry and Climate Change at the UK Forestry Commission’s Forest Research agency, said: “Trees and forests are essential to a sustainable future for the Earth, and we welcome this paper’s contribution to our developing understanding of tree density in the world’s major biomes. Valuable Evidence “The findings will provide scientists, forest managers and policy-makers with valuable evidence, although additional information on the size, species and management of the trees in these biomes is needed to inform our view of the forests’ sustainability.” But Martin Lukac, a forest scientist at the University of Reading in the UK, has misgivings. “One of my biggest concerns,” he said, “is the method used to calculate the total number of trees. “The researchers looked only at areas categorised as ‘forest’ to calculate the total number of trees. In the UK, for example, this accounts for only 13 percent of the British land area and ignores the rest, even though we know that Britain has millions of trees growing in areas that would not be classified as forest. “The study states that forests with a higher density of trees store more carbon than those with fewer trees. This is nonsense. In a normal forest, a lot of small trees will store less carbon than fewer large trees. “The previous estimate of trees in the world was 400 billion. The new estimate is 3 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.” YOU MIGHT ALSO LIKE

Science-Based Solutions Reject Boyan Slat’s Approach to Rid the Ocean of Plastic

2 Elephants Killed in National Park Sparks Fear of More Poaching

What the World Would Look Like Without Humans

EcoWatch Daily Newsletter

This image of the Santa Monica Mountains in California shows how a north-facing slope (left) can be covered in white-blooming hoaryleaf ceanothus (Ceanothus crassifolius), while the south-facing slope (right) is much less sparsely covered in a completely different plant. Noah Elhardt / Wikimedia Commons / CC by 2.5

By Mark Mancini

If weather is your mood, climate is your personality. That's an analogy some scientists use to help explain the difference between two words people often get mixed up.

Read More Show Less
Flames from the Lake Fire burn on a hillside near a fire truck and other vehicles on Aug. 12, 2020 in Lake Hughes, California. Mario Tama / Getty Images

An "explosive" wildfire ignited in Los Angeles county Wednesday, growing to 10,000 acres in a little less than three hours.

Read More Show Less
Although heat waves rarely get the attention that hurricanes do, they kill far more people per year in the U.S. and abroad. greenaperture / Getty Images

By Jeff Berardelli

Note: This story was originally published on August 6, 2020

If asked to recall a hurricane, odds are you'd immediately invoke memorable names like Sandy, Katrina or Harvey. You'd probably even remember something specific about the impact of the storm. But if asked to recall a heat wave, a vague recollection that it was hot during your last summer vacation may be about as specific as you can get.

Read More Show Less

A film by Felix Nuhr.

Thailand has a total population of 5,000 elephants. But of that number, 3,000 live in captivity, carrying tourists on their backs and offering photo opportunities made for social media.

Read More Show Less
Scientists have found a way to use bricks as batteries, meaning that buildings may one day be used to store and generate power. Public Domain Pictures

One of the challenges of renewable power is how to store clean energy from the sun, wind and geothermal sources. Now, a new study and advances in nanotechnology have found a method that may relieve the burden on supercapacitor storage. This method turns bricks into batteries, meaning that buildings themselves may one day be used to store and generate power, Science Times reported.

Bricks are a preferred building tool for their durability and resilience against heat and frost since they do not shrink, expand or warp in a way that compromises infrastructure. They are also reusable. What was unknown, until now, is that they can be altered to store electrical energy, according to a new study published in Nature Communications.

The scientists behind the study figured out a way to modify bricks in order to use their iconic red hue, which comes from hematite, an iron oxide, to store enough electricity to power devices, Gizmodo reported. To do that, the researchers filled bricks' pores with a nanofiber made from a conducting plastic that can store an electrical charge.

The first bricks they modified stored enough of a charge to power a small light. They can be charged in just 13 minutes and hold 10,000 charges, but the challenge is getting them to hold a much larger charge, making the technology a distant proposition.

If the capacity can be increased, researchers believe bricks can be used as a cheap alternative to lithium ion batteries — the same batteries used in laptops, phones and tablets.

The first power bricks are only one percent of a lithium-ion battery, but storage capacity can be increased tenfold by adding materials like metal oxides, Julio D'Arcy, a researcher at Washington University in St. Louis, Missouri, who contributed to the paper and was part of the research team, told The Guardian. But only when the storage capacity is scaled up would bricks become commercially viable.

"A solar cell on the roof of your house has to store electricity somewhere and typically we use batteries," D'Arcy told The Guardian. "What we have done is provide a new 'food-for-thought' option, but we're not there yet.

"If [that can happen], this technology is way cheaper than lithium ion batteries," D'Arcy added. "It would be a different world and you would not hear the words 'lithium ion battery' again."

Aerial view of the Smithsonian Tropical Research Institute in Gamboa, Panama, where a new soil study was held, on Sept. 11, 2019. LUIS ACOSTA / AFP via Getty Images

One of the concerns about a warming planet is the feedback loop that will emerge. That is, as the planet warms, it will melt permafrost, which will release trapped carbon and lead to more warming and more melting. Now, a new study has shown that the feedback loop won't only happen in the nether regions of the north and south, but in the tropics as well, according to a new paper in Nature.

Read More Show Less

Trending

Marion County Sheriff Billy Woods speaks during a press conference after a shooting at Forest High School on April 20, 2018 in Ocala, Florida. Gerardo Mora / Getty Images

By Jessica Corbett

A sheriff in Florida is under fire for deciding Tuesday to ban his deputies from wearing face masks while on the job—ignoring the advice of public health experts about the safety measures that everyone should take during the coronavirus pandemic as well as the rising Covid-19 death toll in his county and state.

Read More Show Less