When faced with deforestation statistics that seem daunting, the fact that there are 422 trees per person on Earth sounds a bit more reassuring. But is it?
On Wednesday, researchers published the most comprehensive assessment of global tree populations ever conducted, revealing findings that blew previous estimates out of the water. Prior to the Yale-led study, Earth was believed to be home to 400 billion trees, but the new estimate is nearly eight times higher – 3.04 trillion. Researchers arrived at this estimate based on data collected from satellite imagery and ground-based tree density estimates from more than 400,000 locations worldwide.
But while this magnitude of newfound trees sounds promising, the reality is actually not as bright. “The number of trees has fallen by about 46 percent since the start of human civilization,” said Yale University ecologist Thomas Crowther, lead author of the study, in an interview with Reuters. “Each year there is a gross loss of 15 billion trees and a net loss of 10 billion.”
In fact, today's 3.04 trillion tree estimate is the lowest number of trees since the start of human civilization according to Dr. Crowther. Trees fulfill many necessary functions in the ecosystem including stabilization of soil and absorption of carbon dioxide, but humans often take these prominent organisms for granted.
“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,” according to a Yale University statement.
Historically, land conversion for agriculture has contributed the most to deforestation, but this has shifted as more and more forests are impacted by industrial and urban development.
These are issues humans can theoretically fix, but “as the global human population grows, the net loss of trees worldwide also may increase,” Yale researcher Henry Glick told Reuters. The study confirms that tree densities typically nosedive as human population increases, understandably so since more people means the need for more cleared land.
“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 in the Yale statement. “This study highlights how much more effort is needed if we are to restore healthy forests worldwide.”
Beyond tree research, insights from this study can extend to large-scale system modeling, from climate change models to carbon cycling.
The researchers' findings were published Wednesday in the journal Nature.
This report includes material from Reuters.