In the 2004 Presidential election, environmental issues were essentially absent from the political discourse. Not so this year, with both parties' candidates vowing to treat our national petroleum addiction and shrink our bloated carbon footprint.

These promises are a refreshing breeze after eight years of stagnation and obfuscation (stagfuscation?) in the executive branch. But there is one vital environmental word that you haven't heard the candidates say: biodiversity. Biodiversity is the variety of life on Earth, from genes to species, and like the world's glaciers, it is melting away.

Estimates of the rate at which we're extinguishing species vary widely. It might be one thousand species per year; it might be ten thousand or more. The precise number doesn't matter: it is unknown and unknowable. What we do know is that we're hemorrhaging habitat in megadiverse tropical rainforests and elsewhere, and that when habitat disappears, so do species and genetically distinct populations.

All of this raises a question: Who cares?

We are not being facetious. We are asked this question all the time--by friends, by journalists, by children. "I mean, why do these species matter to us?" Even committed environmentalists can struggle to answer this question persuasively. But that is not because there are no compelling answers; it is because we as a society don't think or talk much about what biodiversity means and what it does for us.

The easiest way to answer the question, "What good are species?" is to cite the various material benefits that biodiversity provides. Honeybees made headlines last year when their colonies started disappearing for no apparent reason, threatening our $14-billion crop-pollinating industry and raising the prospect of almond-croissant and blueberry-pie shortfalls. But lost in the buzz over honeybee decline was the story of how we came to be so reliant upon this one single bee species from Europe, namely that we have made the agricultural landscape inhospitable to our native pollinating insects, effectively incarcerating them in small remnant habitat patches. Recent experiments suggest that when natural habitat adjacent to agricultural fields is conserved, native bees do a better job pollinating our breakfast--and the more bee species, the more effective they are.

Conserving biodiversity is literally a healthy thing to do. Naturally occurring chemicals in obscure plants and animals have been spun into various life-saving drugs; perhaps the most famous is the rosy periwinkle, native only to Madagascar, from which we took the compounds vincristine and vinblastine to fight lymphoma and breast cancer.

We could go on with examples for pages, and those examples are but a tiny fraction of those to come. Somewhere in some forest right now, an even better cancer treatment is laying its eggs on the leaves of a beverage ten times better than coffee. Buying time for those species' properties to be discovered is one good reason to conserve all the species we can.

But there is a hitch here. For all of the thousands of past and future instances of wild organisms bettering our lives, there are also millions of species that do not tend our crops, cure our cancers, or keep us awake long enough to file our taxes.

So why do we need polar bears and mountain gorillas, spotted owls and sunbirds? Why do we need checkerspot butterflies, delta smelt, damselflies, or Florida's endangered perforate reindeer lichen?

We "need" these things like we "need" color vision, libraries, art, music, and universities. None of them is indispensable. Yet each of them stimulates us, embodies tremendous information, makes our lives better in tangible and intangible ways. Biodiversity is the only one that we appear willing to decimate.

Here is a fact about being human. There is nothing more exhilarating--no matter who you are--than staring down a buffalo, a bull moose, or a bear. Not everybody is lucky enough to experience those things. Some of us experience something like that once, and that single experience becomes a story that is re-told, and a memory that is re-lived, for a lifetime. But the more one learns about wild organisms, the easier it is to find excitement, inspiration, and adventure outdoors. Viewed in light of the intricate symbiosis that they represent, even reindeer lichens are charismatic.

We humans have already done a number on biodiversity. Fortunately, we're still sitting on a big pile of fascinating biological chips, and there is absolutely no need to cash them in for the sake of short-term economic growth. When we outspend the budget, we do not close down the state university. When the room is cold, we do not burn books. Every human threat to the beautiful, fascinating, bewildering diversity of life on earth is solvable in a way that will leave humanity happier, healthier, and wealthier.

But if we don't broaden our conception of the environment beyond "Environment and energy," we won't find these solutions until much more has been lost.