We’ve got some good news and bad news for nature lovers. The good news is, scientists have calculated the number of known plant species, and there are so many out there, you could spend the rest of your life hiking through rainforests and national parks without running out of fascinating flora to identify. The bad news is, 21 percent of plant species are at risk of extinction.

The BBC reports that researchers at the Royal Botanic Gardens, Kew recently released a far-reaching report [PDF] on the state of the world’s plants. They not only tallied up the number of plant species currently known to scientists, but identified the major threats to flora around the world. The report isn’t the first to calculate the number of known plant species, but it is the most up-to-date, and likely the most accurate. Researchers combed through multiple databases, making an effort to eliminate redundancies and repetitions, and added in 2034 new plant species discovered in 2015.

The researchers estimated that there are, in total, 390,900 known plant species in the world, and of those approximately 369,400 are flowering. Unfortunately, many are at risk as habitat changes, climate change, disease, and pests all had (and continue to have) a negative impact on plant survival around the world. According to the researchers, invasive species posed one of the largest risks, both to plants and to the world economy. The report explains that there are 4979 invasive species in the world, and that the estimated cost of their damage and removal is approximately five percent of the world economy.

"Invasive species are really one of the biggest challenges for native biodiversity," Colin Clubbe, head of conservation science at Kew, told the BBC. "Now that we've got this list and this number, it's certainly a bit like know your enemy.”

Kew plans to conduct its State of the World’s Plants study annually, and hopes to continue identifying threats to the world’s fauna and contributing solutions.

In the introduction to the study, the RBG Kew's Kathy J. Willis and Steve Bachman write: “... by bringing the available information together into one document, we hope to raise the profile of plants among the global community and to highlight not only what we do know about threats, status and uses, but also what we don’t. This will help us to decide where more research effort and policy focus is required to preserve and enhance the essential role of plants in underpinning all aspects of human wellbeing.”

[h/t BBC]