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ST. LOUIS  • You might know the towering sentinels of California's redwood forests as giant sequoias. A botanist might use the scientific handle: Sequoiadendron giganteum.

But, somewhat confusingly, a botanist also might call these familiar, iconic trees by one of 18 other scientific names. Therein, botanists say, lies a frustrating problem of global consequence, one that researchers at the Missouri Botanical Garden have worked to fix.

Today, the garden, along with England's Royal Botanic Gardens, Kew, are releasing an enormous online database called "The Plant List" that, for the first time, attempts to catalog all the world's plants and their names. First conceived at the International Botanical Congress held in St. Louis in 1999, the list will function partially like a dictionary, partially like a thesaurus, and its developers believe it will become a critical reference for science, agriculture and conservation.

"There's no one place that you can look for all the names of all the plants in the world, but this is such a place," explained Peter Raven, president emeritus of the garden. "Finally, you have one steady reference, and of course, the names are fantastically important because whatever you do with plants, from medicine to agriculture, depends on those names."

Scientists know, with a certain degree of accuracy, how many animals roam the world. They have counted mammals, amphibians, birds and butterflies and maintained lists of them for a quarter-century. But they have never had a working list of plants, a single portal, until now.

"It's surprising to people in general, including many professional botanists, that we don't have a list," said James Hanken, director of Harvard University's zoology museum. "We estimate we have 1.8 million named species — and I say 'we estimate' because that's more than a guess, it's a reasonable calculation. But it's not like there's a list in one place."

DAUNTING CHALLENGE

Counting plants is a tricky business, and not just because of the sheer number of them. When plants are discovered or identified, they are given a scientific name according to certain naming conventions that have been in place since the 18th century. But over time, many plants have been called by many different scientific names in different parts of the world.

"There are a million plant names out there with many species having many names applied to them," explained Peter Wyse Jackson, president of the garden. "I've worked on various islands in the Caribbean, and on one island they call a plant by one name, and on another, by another."

This poses obstacles for researchers.

Alan Paton, assistant keeper of the Herbarium Library, Art and Archives at Kew, explained that by using one name, a researcher might pull up as little as 20 percent of the available information on a plant. "If one country is recording the results under one name, and another is recording it under another, you've lost the information flow," Paton said. "Mapping together the different names really facilitates an understanding of the plant's use and how to conserve it. The name is really how you find out about a plant."

The name also allows researchers get a grasp of the quantity of the world's flora. The Plant List includes 1.25 million scientific plant names. Of these, roughly 300,000 are validated names for the species they identify, while 480,000 are duplicates, or synonyms. As the list develops and more data emerge, the remaining 440,000 or so names will be clarified.

"It's the first-ever list, so it's a starting point," said Wyse Jackson. "But it does allow us ... to make a good estimate of the total plant species on the planet."

The figure, Wyse Jackson said, is about 400,000, though that number is in flux, as 20,000 to 30,000 new plants are discovered every year, while thousands disappear.

FOOD AND MEDICINE

Jackson called the list "absolutely essential" to important, even life-sustaining work.

"For example, we know there are 10,000 to 20,000 plant species used for medicinal purposes around the world, and 20,000 for food," he said. "Unless we have an understanding of the diversity of the plants, we can't ensure their conservation. We're faced with a situation where about a quarter of the world's plants are threatened, so this is going to be critical."

The list combines databases maintained by Kew and the Missouri Botanical Garden, melded with those maintained by other research institutions and projects. Missouri has maintained its database, known as Tropicos, since the early 1980s.

"We took the two largest resources and joined them together using business rules," Paton said, 'so if two databases disagreed, we could resolve the conflict. You have to work out what content matches and what doesn't match."

For example, the list's compilers would look at one group of plants from Peru and the same in Ecuador, finding 'synonomies" — different names for the same plant — using computer processes and bioinformatics.

"The system we have of naming plants starts in the 1750s, and since then people have gone on describing them and naming new ones," Raven said. "But then this [project] begins in a way that's possible with all this new technology."

The list will have to be updated and improved continuously. The next goal is to complete a comprehensive list of all the world's flora by 2020, though even then it will change with new discoveries and extinctions.

"We realized it wasn't possible to get a perfect list," Paton said. "But if we had at least a working list, it would be a major step forward."

To see the list go to: www.theplantlist.org

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