As scientists meet to discuss climate change, David Campbell says we can preserve diversity in Amazonia by following the lead of international cooperation in Antarctica

The virtue of this planet, which distinguishes it from most, if not all, of the rest of the cold, indifferent universe, is life. As a biologist, I celebrate life. And as a biogeographer, I have had the good fortune to conduct research all over the face of this lovely orb, including in those antitheses of biological diversity: Antarctica and Amazonia. This is a privilege that would have been unimaginable to my antecedents only a generation ago. Mine is an age of easy discovery (although not necessarily enlightenment).

I came to the Amazon to explore one of the great and enduring conundrums of nature: how so many species of plants and animals can coexist in one small area. The Amazon River and her forest are like no other place, the last continent-sized stretch of untrammelled wilderness on Earth, and the greatest expression of the planet's biological diversity. Just one of my 2-hectare study sites in western Amazonia is home to more species of tree than occur in all of North America; more species of bird than exist in all the UK; and more species of insects than we can count. The Amazon Valley, in fact, harbours more species of plants and animals than have ever existed - at any time, anywhere - during the 4 billion-year history of life on Earth.

Yet, just at this peak of biotic eloquence, it appears inevitable that most of this biological heritage will be lost. Over the next few decades, Amazonia will lose hundreds of thousands - perhaps millions - of species.

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Perhaps every planet with intelligent life must endure this tragic adolescence, when her children run amok. Even if we temper our appetites, only a few scraps of wilderness are likely to survive. Ours may be the last generation to live in a world where adventures such as mine, to remote, unpeopled regions and to places of extravagant biological diversity, are possible.

Taxonomists are still conducting the inventory of Amazonia, naming its abounding species. The job is far from complete, and today we scientists are forced to decipher pattern and process in a place where many (if not most) species remain undescribed and their functions unknown. It hasn't always been this way. Before the European conquest of Amazonia, there were millions of Native Americans, diversified into hundreds of tribes. Each indigenous culture had its own taxonomy to assort the panoply of diversity, to assign it order.

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But today the Amazonian forest is an unnamed place. The native Amazonians (who now number only about 200,000) are losing their languages and cultures at the same time as they are losing their biological heritage. They have forgotten thousands of the words once used to describe this forest. Now we must rename the parts of Amazonia and construct a new taxonomy, but we are only beginning to grope our way through this aphasic New World. How can anyone achieve wisdom in a place that has no human voice to represent it, no scaffolding of words on which to hang things? What is a forest with no names for its parts? This may explain the terracide I see there: it's hard to love a place that cannot be defined in language and therefore cannot be understood. Yet it is easy to give away something for which there are no words, something that you never knew existed.

Most of the destruction of Brazilian Amazonia occurred during the dark years of military rule, in the Sixties and Seventies, as the consequence of a programme of paranoiac "national integration" that sliced through Amazonia with extensive highways from the Atlantic to the foothills of the Andes. The military regime was staunchly supported by the urban oligarchy in Brazil's south. The roads became conduits for ill-conceived colonisation schemes, homesteads built on senile soils that were not conducive to agriculture. The homesteads soon collapsed, and the once hopeful settlers had to move on, becoming nomadic environmental refugees, a restive population that persists to this day.

The highway schemes also threw Brazil into chronic international debt - the greatest of any nation - leading to the short-term (but foreign revenue-generating) economics of timber extraction, mining, ranching and hydroelectic schemes. Whole mountains were razed; whole biotas cleared; whole river valleys drowned. As a consequence, much of eastern Amazonia has been destroyed and thousands of species have been lost - for the most part anonymously.

But it's not all bad news. Since the Eighties, Brazil's resurrected democratic tradition has spawned many idealistic politicians and grassroots civil organisations: a coalition of Amazonians, Native Americans and educated urbanites in the nation's south. No longer afraid to speak out, they reject the bankrupt economic schemes of the military years and are demanding that development in Amazonia respect its biological heritage and the rights of its native people. Their affection for the place is as much aesthetic as economic. Amazonia is becoming a world centre for environmental tourism. Amazonia is becoming a place to cherish.

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In contrast to the grandiloquence of Amazonia, Antarctica is a biological haiku. We have named its parts, and there aren't many. There are more species of lichens, liverworts, mosses and algae growing on top of a single leaf of an Amazonian palm than there are growing on the entire continent of Antarctica. My journeys to the Antarctic continent have taught me what Earth was like before it was mantled in life. And my research on the invertebrates that live off of the coastline of King George Island, which the ebullient, fertile sea washes around the clock, taught me how life can prosper just about anywhere. I came to that cold sea to study the pathogens of Antarctic krill, the small shrimp-like crustacean that is the keystone to most Antarctic marine food chains. There is only one short link in the food chain between a single-celled photosynthetic diatom and a 91,000kg blue whale - between one cell and the largest of all animals - and that link is the Antarctic krill. This is one of the simplest food chains on Earth, but the numbers involved are astounding. An adult blue whale eats up to 3,600kg of krill a day over a four-month Antarctic summer: in all, about half a billion individual krill. Collectively, these krill have, during their lives, filtered from the sea perhaps 10 billion billion diatoms. This is the same order of magnitude as the number of stars in the universe.

So far, no species of plant or animal has become extinct in Antarctica because of human activity. Regardless, highly productive but low-diversity ecosystems such as the Southern Ocean are particularly susceptible to human interference. For example, the increased flux of ultraviolet light due to ozone depletion over the Southern Ocean has shifted the population of diatoms toward species that have thick silicon shells that filter out the harmful rays. Krill find these heavily armed algae hard to digest. As a result of this and other factors, the population of Antarctic krill has declined 80 per cent in recent years. Necessarily, when the numbers of that keystone species decline, so do the numbers of every organism downstream in the food chain - from penguins to seals to whales.

But there's good news in Antarctica. The 1987 Montreal Protocol regulates the release of ozone-destroying chlorofluorocarbons. And the 1959 Antarctic Treaty, forged in the darkest days of the Cold War, has become an exemplar of sensible world governance.

These days King George Island is home to the research stations of ten nations: Argentina, Brazil, Chile, the Czech Republic, Germany, the People's Republic of China, Poland, Russia, South Korea and Uruguay, which all share the same sparse shoreline. Collectively, these nations fought eight wars among themselves during the 20th century. Now, at the bottom of the world, they share an improbable camaraderie, placing their territorial claims in abeyance and learning to live peacefully and cooperatively as neighbours. Antarcticans have laid down the tooth-and-claw lessons of savanna and forest, of city-state and nation-state and, by necessity, learnt tolerance.

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Likewise, the citizens of the nine nations that share Amazonia must understand that they are guardians of a place that is not just an irreplaceable domestic heritage, but an earthly one, too. All these nations service onerous international debts that drive them toward short-term economic gains at the expense of their biological treasures. One could argue that they have the right to raze their forests, just as our ancestors in the North did a century before. But our ancestors didn't live in the hyperdiverse tropics and, their activities didn't have the potential to alter the trajectory of life on Earth.

Today, we in the North hold the debts incurred by those nations endowed with tropical splendour. We must forge a mutually respectful covenant with our Southern brethren, find the political will (and compassion) to forgive those debts and provide tropical nations with viable economic incentives to preserve, not despoil. Such an act would be both a service to them, to ourselves and to all humanity. To do anything less would be terracide.

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David Campbell is professor of biology and chair of environmental studies at Grinnell College, in Iowa. This essay is derived from two of his books: The Crystal Desert: Summers in Antarctica (Secker and Warburg, 1993) and A Land of Ghosts: The Braided Lives of People and the Forest in Far Western Amazonia (Jonathan Cape, 2004).