How many different plants and animals can fit in a little Island like Bermuda, without falling off the edge? We are now learning that tropical rain forests contain millions of distinct species of trees, orchids, spiders, butterflies, bats and birds -- one tree in Brazil may be home to more ant species than there are in all of Great Britan.

Coral reefs are like a jungle underwater; they are built by, and provide food and shelter to zillions of colourful critters, from the lowly coral polyps up to the peanut worms, clown shrimp, angelfish, and nurse sharks.

Scientists have estimated that there are maybe 25 million species of bacteria, plants, fungi and animals alive today, of which fewer than two million have been seen, caught, and given a Latin name.

The more tropical the climate, it seems, and the larger and more geographically diverse an area in, the more biological diversity if contains.

Bermuda is sort of tropical all right (well, subtropical is the more correct term), and its shallow reefs extend over a respectable 750 square kilometres.

As expected, we have lots of different marine creatures; not as many as say in the middle of the warm Caribbean, but nevertheless enough to build coral reefs teeming with fish, mangrove forests whose roots are covered with weeds and sponges, and seagrass meadows that feed conchs and turtles.

I have attempted to count all the species that have ever been found in Bermuda's waters, from wheel animalcules to whale sharks, and come up with 4597.

That's not bad at all, considering Hawaii in the Pacific Ocean, which is made up of many islands with high mountains and deep valleys, has no more that 6254.

Maybe our marine diversity is not doing so badly because we have a lot of shallow reef area, of which most is far away from that tiny sliver of land we call Bermuda, and therefore better protected from us.

There is no reason to rejoice, thought, when we remember that the Island's first settlers found so many sea birds nesting here that they literally stumbled over them and rockfish so large and plentiful that people were afraid to step into the water for fear of being swallowed -- and how all this bountiful life was harvested near-extinction within less than a decade.

Only careful attention to the many threats -- from sewage, garbage and dock construction to degrading and overfishing -- will ensure that our marine environment can continue to thrive.

As we might have expected, Bermuda's small land area does not support a lot of diversity.

Only 3,702 species of plants, snails, spiders, insects and lizards have ever been recorded, compared with the more than 15,000 in Hawaii.

Land creatures also compete with us humans for living space; no wonder we have already pushed many of them over the edge, and have nearly lost others as precious as the cahow, Bermuda cedar tree, and the skink.

With every new building that goes up, every bit of land that is cleared, and every square foot of soil that is covered with asphalt, countless living things great or small are losing food and home.

As we celebrate the 30th anniversary of Earth Day this week, remember it will require the care of all of us to stem future extinctions, and make sure that our irreplaceable natural heritage continues to live with us in partnership.

Our Bermuda Biodiversity Project at the Aquarium has begun to catalog and protect Bermuda's many life forms; let us know if you are interested, and we will tell you more about it! Wolfgang Sterrer is the Curator of the Bermuda Natural History Museum Deep sea creatures: Mushroom corals, found in the Pacific Ocean off a California, inhabit waters way too deep for humans, This one was found at 3,3000 feet in Monterey Bay.

Coral crowd: Fish swim through Australia's Great Barrier reef. The reef down under one of the world's greats natural wonders, but like all reefs worldwide, faces threats from pollution and global warming.