The polar bear has long been a symbol of the damage wrought by global warming, but now biologist Andrew Derocher and his colleagues have calculated how long one southerly population can hold out. Their answer? No more than a few decades, as the bears’ decline closely tracks that of the Arctic’s disappearing sea ice.

The images of pelicans and other Gulf of Mexico seabirds drenched in oil have stirred sadness and outrage around the world. But, says conservationist Melanie Driscoll, the unseen effects are probably far greater, with some birds perishing out of sight, far from shore, and others facing spill-related declines in the fish on which they depend.

The massive oil spill in the Gulf of Mexico is a warning, conservationists say, of what could happen in the Arctic as melting sea ice opens the Arctic Ocean to oil and gas drilling. Many experts argue that the time has come to adopt an Arctic Treaty similar to the one that has safeguarded Antarctica for half a century.

The tropical forest conservation plan, known as REDD, has the potential to significantly reduce deforestation and carbon dioxide emissions worldwide. But unless projects are carefully designed and monitored, the program could be undercut by shady dealings at all levels, from the forests to global carbon markets.

Among the natural treasures at risk from the oil spill in the Gulf of Mexico is the Breton National Wildlife Refuge, created by Theodore Roosevelt to halt a grave threat to birds in his era — the lucrative trade in plumage. Now, oil from the BP spill is starting to wash up on beaches where Roosevelt once walked.

Our high-tech products increasingly make use of rare metals, and mining those resources can have devastating environmental consequences. But if we block projects like the proposed Pebble Mine in Alaska, are we simply forcing mining activity to other parts of the world where protections may be far weaker?

The pronghorn, a close relative of the antelope, is the fastest mammal in North America and an iconic creature in the American West, where an estimated 700,000 roam the high desert and plains. In recent years, however, intensive development has begun to eat away at the pronghorn’s territory. In a video report for Yale Environment 360, journalists Daniel Glick and Ted Wood examine the fate of a herd of pronghorn that has migrated for more than 6,000 years from the Grand Teton Mountains to their wintering grounds.

As burgeoning human populations place greater pressure on wild areas, a strategy is emerging for preserving threatened lands and wildlife. Known as ‘rewilding,’ it involves expanding core wilderness areas, connecting them via corridors that allow humans and animals to co-exist, and protecting and reintroducing top predators.

Although it is a heavily urbanized nation, fully two-thirds of Japan remains woodlands. Yet many of the forests are timber plantations inhospitable to wildlife, especially black bears, which are struggling to survive in one of the most densely populated countries on Earth.

Wildlife biologists and climate scientists overwhelmingly agree that the disappearance of Arctic sea ice will lead to a sharp drop in polar bear populations. But some skeptics remain unconvinced, and they have managed to persuade the Canadian government not to take key steps to protect the animals.

With global warming pushing some animals and plants to the brink of extinction, conservation biologists are now saying that the only way to save some species may be to move them.

Aided by new access to remote regions, researchers have been discovering new species at a record pace — 16,969 in 2006 alone. The challenge now is to preserve threatened ecosystems before these species, and others yet unknown, are lost.

The international commission charged with protecting the giant bluefin tuna is once again failing to do its job. Its recent decision to ignore scientists’ recommendations for reducing catch limits may spell doom for this magnificent and endangered fish.