"It's an interactive zoo," said James Edwards, who will be the encyclopedia's executive director. Edwards currently helps run a global biodiversity information system.

If the new encyclopedia progresses as planned, it should fill about 300 million pages, which, if lined up end-to-end, would be more than 52,000 miles long, able to stretch twice around the world at the equator.

The MacArthur and Sloan foundations have given a total $12.5 million to pay for the first 2 1/2 years of the massive effort, but it will be free and accessible to everyone.

The pages can be adjusted so that they provide useful information for both a schoolchild and a research biologist alike, with an emphasis on encouraging "citizen-scientists" to add their sightings. While amateurs can contribute in clearly marked side pages, the key detail and science parts of the encyclopedia will be compiled and reviewed by experts.