OUR forests are the heart of our environmental support system. And yet, in the 36 years that have passed since the first Earth Day, on April 22, 1970, we have lost more than one billion acres of forest, with no end in sight.

The people most vulnerable to the disappearance of forests are the poor: nearly three-quarters of the 1.2 billion people defined as extremely poor live in rural areas, where they rely most directly on forests for food, fuel, fiber and building materials. But those of us in the developed world are hardly immune. Smaller forests mean fewer predators keeping insects and rodents in check in the Northeastern United States, a phenomenon linked to the spread of Lyme disease and West Nile virus, among others.

Everywhere, forests prevent erosion, filter and regulate the flow of fresh water, protect coral reefs and fisheries and harbor animals that pollinate, control pests and buffer disease. That is why the single most important action we can take to protect lives and livelihoods worldwide is to protect forests. And one of the best ways to do that is to change how we think about their economics.

First, we must connect local, informal foresters, who harvest timber and other forest products for a small fraction of their value, to better markets. A good example is in Papua New Guinea. A community there receives about $13 for a cubic meter of tropical hardwood. That same cubic meter of wood, transferred through a series of intermediaries, shows up in New York Harbor with a new price tag, $700. Minimally processed into thin veneer, it sells for $2,300. That same cubic meter, fully finished, goes for over $3,000. Small forest holders who receive just pennies on the dollar for a valuable natural resource can hardly be expected to practice sustainable forestry. Opening access to regional and global markets at fair value will create strong incentives for sustainable forest management.

Second, we must recognize the importance of forests in maintaining water and soil by encouraging their preservation along rivers. Markets can help here, as well. Costa Rica's hydroelectric power companies pay upland farmers to keep land forested to prevent the companies' dams from filling with silt. The cost is shared between a power company and its customers. Logic dictates that those who benefit when forests stop erosion should return some of those benefits to those who protect forests.

Third, we must seek a global trade agreement that promotes legally, sustainably harvested timber. We should not tolerate the forest destruction abetted by most countries, which will neither monitor what is extracted at home, nor place conditions on imports. When we first visited Sumatra and Borneo fewer than 20 years ago, there were vast tracts of forest. Recent estimates indicate that these two islands, among the six largest in the world, could be largely clear-cut by 2012. With those trees will go people's livelihoods, communities, cultural values and health, as well as the forests' unexplored biological diversity.

Finally, we must protect the role that forests play in mitigating global warming by absorbing carbon dioxide, a greenhouse gas. Markets for trading carbon dioxide emissions credits must expand to all sources and all nations. They already exist in the developed world, where yesterday morning carbon credits from efficient factory operations and tree re-planting projects were traded at roughly 30 euros per ton.

If a company in Belgium can own carbon credits because it has reduced its factories' carbon emissions, then a forest owner in the Central African Republic should be able to trade the carbon credits he earns by not cutting down its trees. To the atmosphere, a ton of carbon is a ton of carbon. By opening trade in carbon credits to all countries, we provide economic opportunity to developing nations and create a very powerful incentive to conserve forests.

Together, these measures have the potential to reverse rates of forest loss. Sustainable forests, in turn, can form the basis for the health and economic well-being of the poorest among us, while benefiting everyone else as well. What could be a more satisfying vision for Earth Day 2006?

Don Melnick is a professor of conservation biology at Columbia University. Mary Pearl is president of Wildlife Trust.

Hal, the year-old coyote who died in custody after leading the authorities on a gripping chase through Central Park last month, was seriously ill from a heartworm infestation and internal hemorrhaging caused by rat poison, according to the results of a necropsy released yesterday by the State Department of Environmental Conservation.

On March 30, 10 days after he was first sighted in Central Park and 8 days after he was captured in an intense pursuit, Hal stopped breathing during a routine tagging procedure by two biologists.

In a statement, the agency said, "His poor health, coupled with the stress of captivity and handling during the release, led to his death."

Paul Curtis, a wildlife specialist at Cornell University whose work focuses on conflicts between humans and wildlife, said, "It was a very sick coyote."

A graduate student of Dr. Curtis's, Dan Bogan, was one of the biologists trying to tag Hal for release into the wild when the coyote stopped breathing. Dr. Curtis said that the procedure caused minimal stress and that Mr. Bogan was experienced in tagging coyotes.

The necropsy added details about Hal's last days, noting that after he was transferred to wildlife rehabilitators on Long Island, he was fed venison, chicken thighs, organ meats, canned dog food and kibble.

It also described the tagging process, saying that after Hal was taken from his carrier and held with a catchpole — a long pole with a plastic-coated-wire loop used to secure animals — his mouth was kept shut with an Ace bandage. "The nose was clear for breathing," the report said. A few minutes later, "during ear-tagging," Hal stopped breathing.

Dr. Curtis said that signs of heartworms, caused by mosquito-borne parasites, are not outwardly visible. He also said it was likely that Hal had eaten a rat or mouse that had ingested poison.