ST. LOUIS • A few years ago, anyone who asked Peter Wyse Jackson how many plant species exist in the world might have been surprised by his response. The botanist didn't know, and neither did the scientific community.
The president of the Missouri Botanical Garden now can safely guess that there are about 400,000 known plants. But that's only because the garden two years ago completed a massive online database dubbed the Plant List.
Today, Wyse Jackson and his counterparts at three other leading botanical gardens will announce the next step in cataloging the world's plants. They plan to add detailed scientific information and images to the list, in effect turning something that's akin to a dictionary into a richly detailed encyclopedia.
Only on a much larger scale.
The catalog, called the World Flora, is intended to be the most complete compendium of plant life that has ever been created. Planners hope to make the World Flora available for free online starting in 2020.
"This is going to be seen by future generations as a landmark project," Wyse Jackson said of the effort, which is being led by the garden and three other institutions — the Royal Botanic Gardens, Kew in London; the Royal Botanic Garden Edinburgh; and the New York Botanical Garden.
Officials with the four gardens recently met to plan their next move and to commit their institutions, and their research manpower, to the project.
The World Flora catalog is a priority of the Global Strategy for Plant Conservation, an effort adopted by the United Nations' Convention on Biological Diversity.
At least 100,000 plant species are believed to be threatened by extinction, and Wyse Jackson believes the World Flora will be a critical tool in saving them.
In addition to describing the world's plants, the catalog will detail each species' geographic distribution and whether it is endangered by climate change, deforestation or other threats.
"This will allow us to prioritize to do what we can to save thousands of plant species." Wyse Jackson said.
Researchers will pull information from botanical catalogs and other scholarly works published over more than a century. But because the World Flora is intended to describe the world's plant life as it exists now, previously published material only will be helpful to a point.
In many cases, researchers will have to set out for the field to determine where rare species currently live, or if they exist at all.
The World Flora has a U.N. mandate, but it doesn't yet have a significant source of outside funding. Wyse Jackson said that won't be an obstacle.
"I never want a lack of money to prevent us from doing what is right," he said, noting that the garden is prepared to throw virtually its entire research staff into the effort.
The four gardens charged with creating the World Flora will be assisted by 25 other scientific institutions that have signed on to the project, said Robert Magill, the Missouri Botanical Garden's senior vice president for science and conservation.
The scope of the project will require a virtual army of botanists and field researchers. There has been no serious effort to catalog the world's plants since the 1920s, and Magill expects many of the world's botanists to be eager to contribute to the World Flora.
"There aren't that many botanists out there, so we're going to need just about all of them," he said.