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In the first undertaking of its kind, scientists have pinpointed the location of the majority of the world's "missing" plant species — research that has unveiled both good news and bad.

The good news is that the majority of the yet-undiscovered plant species on Earth — scientists estimate an additional 15 percent of the world's 336,000 species of flowering plants still languish in obscurity — live in regions that already receive the lion's share of conservation efforts.

"The bad news comes in that these places are under extreme threat," said Lucas Joppa, a scientist with Microsoft Research in Cambridge, England, whose results are published this week in the July 4 issue of the journal Proceedings of the National Academy of Sciences. [Related: 8 of the World's Most Endangered Places]

"These places aren't just places with a lot of species, they're places where habitat loss has occurred to an extreme," Joppa said. "So we've prioritized these places, but the problem is even more serious than we thought. Instead of x number of species, it's x + y number of species."

It's because these unidentified species live in comparatively small numbers in rarified pockets around the globe that they've escaped notice. Think of a cardinal, a showy, plentiful bird with a wide-ranging habitat, versus a tiny, drab-colored bird that lives in only one stretch of forest in Ecuador — it's far easier to find one than the other.

Where the hotspots are

Joppa's research looked at what are known as "biodiversity hotspots" — regions defined, by an influential paper more than a decade ago, as areas around the world that are home to at least 1,500 species found nowhere else on the planet and where at least 70 percent of the natural habitat has been destroyed.

Once those danger zones were identified, the world's conservation organizations naturally focused on those as a priority over other areas, Joppa said. "Basically, they've been trying to figure out where they can get the most bang for their buck around the world in terms of conservation," he said.

Although the hotspot concept revealed areas where identified species were threatened it wasn't known if the world's remaining species — those that have never been described — all lived somewhere else. They could be sitting below the conservation radar, throwing a wrench in the efforts to save Earth's species.

Joppa said his research was a first attempt to quantify those known unknowns. "It's one of the most important elephants in the room for conservation," Joppa said. "Trying to figure out what remains missing is one of the oldest questions in ecology."

To predict where these yet-to-be-found species might dwell, Joppa used a computer model that revealed most of the "missing" species indeed live in biodiversity hotspots. In fact, a whopping 70 percent of the elusive plants live in hotspots in six regions in Central America, South America, southern Africa and Australia.

It didn't have to turn out that way. "We could have found out, 'Oh hey, it turns out the places we've been ignoring have more species than the places we've been concentrating on," Joppa told OurAmazingPlanet.

How the 'missing' were 'found'

Joppa and his co-authors peered back to the beginning of humanity's attempt to classify living organisms, beginning in the 1700s, and followed the path of discovery through history to arrive at their projections for how many plant species actually exist on earth, and, in turn, where the most elusive flowering plants live.

"This is the first model that acknowledges that the species discovery process has an inherent human element," Joppa said. "So things like world wars, and other kinds of massive geopolitical unrest will change the number of species described," because humans are too busy fighting to look for new blooms.

So, if there are indeed more than 50,000 flowering plant species on Earth that no taxonomist has ever pressed in the pages of a book, should anyone care? Why is it important to preserve these species before they're killed off? [Related: 10 Species You Can Kiss Goodbye]

"The more we know about ecosystems and they way ecosystems function, the more we know we don't know," Joppa said. "So in the face of that immense uncertainty, it seems exceptionally foolhardy to be tinkering around with things that we don't fully understand."

Reach Andrea Mustain at amustain@techmedianetwork.com. Follow her on Twitter @AndreaMustain.