In a recently released study published in the scientific journal ‘Nature’, a team of 38 scientists found that the planet houses 3.04 trillion trees, a significantly higher number than the estimated 400 billion. This means that there are roughly 422 trees for every person on Earth, scientists say, but this is still a frightening number, as the research goes on to illustrate that there are now 46 percent fewer trees than there were before humans began the ever accelerating process of deforestation.
When other causes like wildfires and pest outbreaks are taken into account, the paper estimates there are 15.3 billion trees lost each year. While nearly 5 billion of those may grow back each year – making the net loss 10 billion – this is still a substantial amount. Global Forest Watch released data alongside the study on Wednesday from the Univserity of Maryland and Google, revealing that global forests lost 45 million acres last year, “an area twice the size of Portugal.” More than half of the depletion took place in the tropics, not only from the already prominent leader of deforestation like Brazil and Indonesia, but also in countries like Cambodia, Sierra Leone, Madagascar, Paraguay, and Uruguay.
“We can now say that there’s less trees than at any point in human civilization,” states Thomas Crowther, a post-doctoral researcher at the Yale School of Forestry and Environmental Studies and lead author on the research. “Since the spread of human influence, we’ve reduced the number almost by half, which is an astronomical thing.”
Crowther says his work was partially inspired by the Billion Tree Campaign, the reforestation project created by the United Nations Environment Programme in 2006 which is now run by the Plant-for-Planet Foundation. The new information means they will have to plant more trees than they had previously calculated, but Crowther hopes the precise number will inspire the activists to double their efforts.
“They want to generate forests on a global scale, but they had absolutely no baseline information about how many trees they needed to plant to do that.” he says.
However, despite blowing away previous estimates of how many trees are left on the planet, the new research doesn’t really change our understanding of deforestation rates, explains Thomas Lovejoy, a conservation biologist at the United Nations Foundation.
“It does not say there’s more forest. It just says there’s more trees in the forest,” he says, adding that the prior estimates of the amount of trees was related in part to the fact that it would probably not have been possible to conduct this kind of expansive research until now.
Scientists were only able to reach these estimates by combining satellite observations with ground-based ecological work. The satellite imaging determined where the forests were located, utilizing no less than 429,775 separate measurements of the density of trees in various locations, and the field-work dove into them to determine how many trees exist in the multitude of forests. It’s important to note that the study defines “tree” as a woody plant that, at breast height, has a stem that is at least 10 centimetres in diameter.
The research found that trees were most prevalent in the tropics and subtropics, which boast 1.39 trillion trees, while the boreal or northern forests accommodate another .74 trillion and the temperate forests contain .61 trillion. It also shows that boreal and tundra forests most often had a larger tree density than the tropical forests.
“To me, this really emphasizes the potential dynamism of trees in boreal and tundra ecosystems,” Michelle Mack, a forest researcher at Northern Arizona University told The Washington Post. “High tree density indicates potential for a rapid increase in forest cover in response to climate warming.”
In fact, that’s one of the biggest implications of this study – the impact of global warming. As trees grow they pull carbon dioxide out of the atmosphere, so cutting or burning them down releases that carbon right back out. Thus, deforestation is making global warming much worse than it already is, and if we were able to bring the number of trees back up to 6 trillion, rather than 3 trillion, it could considerably dull the effects of climate change. Crowther notes that the new information gathered by the study will be critical in understanding exactly how forest restoration can help us do this.
“We can quantify the fossil fuel emissions. Our ability to quantify the impacts of human land use change and deforestation are so minimal. We have to generate this baseline information about where the carbon is, where the trees are….before we can start generating these numbers.