More than 10% of all tree species on Earth have not been discovered

By JoAnn Adkins

73,000

That’s how many tree species scientists estimate currently inhabit the Earth.

Of those 73,000 tree species, approximately 9,200 are yet to be discovered and nearly one-third of those are very rare, with very low populations and limited distribution, most likely growing in tropical lowlands and mountains.

Biologist Chris Baraloto is part of a team of scientists that produced the estimates.

Baraloto, who has spent more than 20 years working in the Amazon, works primarily in the diverse lowland forests of South America, with principal research sites in French Guiana, Peru and Brazil. He provided one of the largest datasets for the study.

South America, where the Amazon is located, was determined to be the most diverse region for trees and 40 percent of the yet-to-be-discovered species are believed to be there, according to the study.

“It’s surprising that so many species remain to be discovered, and this really creates an urgency for their discovery,” said Baraloto, who is the director of the International Center for Tropical Botany in Florida International University’s Institute of Environment. “The more we can learn about tree species, the better we can optimize and prioritize forest conservation all across the world, especially in light of contemporary threats.”

The scientists say their estimates can help infer evolutionary mechanisms that have generated diversity, so they can predict how species may evolve in the future. This research can also assist in assessing resilience to climate change and managing diversity hotspots.

The estimates were calculated using advanced statistical methods and extensive datasets. These new numbers are 14 percent higher than data previously relied on for species estimates. But in the end, they are only estimates and Baraloto said all efforts to fill data gaps should be pursued to provide insights about the diversity of life on the planet and its needed conservation.

One of the most fundamental questions in ecology is how many species inhabit the Earth.

However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown.

Based on global ground-sourced data, the scientific team estimates the total tree species richness at global, continental, and biome levels.

Roughly 40% of undiscovered tree species are in South America.

Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution—likely in remote tropical lowlands and mountains.

These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.

The research was published in PNAS.