Michael Dobie Michael Dobie is a member of the Newsday

Michael Dobie is a member of the Newsday editorial board.

His name is Sudan. He's 42 years old and lives in Kenya, protected 24/7 by armed guards.

Sudan is a northern white rhinoceros, the last known male of his kind in the world. Think about that. The last.

He lives with two females at a conservatory. A tiny handful of female northern white rhinos -- perhaps five -- live elsewhere in captivity. That's it.

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Which means the survival of this subspecies is up to Sudan. Who is old. With a low sperm count. And, perhaps, too weak to mount a female.

Sudan is the forlorn face of a crisis largely of our own making -- the crisis of extinction.

Earth is experiencing a mass extinction of animals and plants, the worst since the dinosaurs vanished 65 million years ago, says the Center for Biological Diversity. True, extinction is a natural phenomenon -- one to five species disappear naturally per year. But scientists estimate we're now losing dozens of species every day, many we know nothing about.

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The reasons are familiar, often interrelated and all about us humans. We cut down forests and plow prairies. We overharvest fish and mine the ocean floor. We pollute and produce devastating climate change. And we hunt.

Poaching decimated many species of rhinos, and elephants, too. The northern white rhino's horn is prized in Asia for its supposed medicinal properties, despite research debunking virtually all of those claims. Sudan's horn has been removed for his protection.

What the pace of extinction says about us is disturbing. So many of our species don't seem alarmed about our scary ability to eliminate other species. We muster protest for nature's icons, like elephants or apes. But we shrug when an insect or plant vanishes. We're humans, it's our world, get out of the way. The arrogance is appalling.

Sometimes, the effects of our actions are plain to see. Take the wolves of Yellowstone National Park, hunted and poisoned to extermination in the park by 1926. Without wolves, Yellowstone's elk population boomed, with disastrous effects. Elk are voracious grazers. The decline of vegetation led to the disappearance of songbirds and beavers. Without the ponds created by beaver dams, otters, muskrats and moose declined. So did mice, voles and pronghorn fawns, prey for the coyote that blossomed without the wolves. When the wolves were reintroduced in 1995, the damage was reversed.

Nature establishes balances we should respect. Extermination throws that out of whack. Already, scientists worry about the variety of life in Africa's savanna grasslands, maintained in part by rhino feasting.

Just as troubling is when we don't know what we're losing. Literally, do . . . not . . . know.

Plants, for example, are a huge source of medicinal drugs for everything from malaria to pain. Rainforest plants offer hope in the fight against cancer. Edible species become dietary supplements.

The non-reflective eyes of moths are inspiring designs for more efficient solar panels. Dirt from a grassy field in Maine harbored an antibiotic that killed the staph infection MRSA and drug-resistant tuberculosis in tests on mice.

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Why do we snicker when environmentalists worry about developments that threaten endangered species like the tiger salamander or snail darter? Our ecosystems are complex. One extinction can lead to another. How much do you really want to kiss goodbye?

It's an amazing world out there. We don't even know how amazing it is yet.

You don't know what you've got till it's gone?

It's worse when you don't even know what's gone.

Michael Dobie is a member of the Newsday editorial board.