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.

Primatologist Patricia Wright has spent the past 25 years studying — and protecting — Madagascar’s rich yet highly threatened biodiversity. Now, as many of the island’s remaining forests are being felled in the wake of a 2009 coup, Wright describes how she is helping organize the local residents and international conservation organizations to fight back.

Many energy experts contend natural gas is the ideal fuel as the world makes the transition to renewable energy. But since much of that gas will come from underground shale, potentially at high environmental cost, it would be far better to skip the natural gas phase and move straight to massive deployment of solar and wind power.

Large corporations, not small-scale farmers, are now the major forces behind the destruction of the world’s tropical forests. From the Amazon to Madagascar, activists have been directing their actions at these companies — so far with limited success.

In the wake of the failed Copenhagen summit, prospects for cutting global CO2 emissions are worse than they’ve been in years. With talk of mandated cuts now fading and with countries exploiting loopholes, the world appears headed toward a flawed agreement based not on science but on politics.

As utilities seek to build new nuclear power plants in the U.S. and around the world, the latest generation of reactors feature improvements over older technologies. But even as attention focuses on nuclear as an alternative to fossil fuels, questions remain about whether the newer reactors are sufficiently foolproof to be adopted on a large scale.

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.

For years, free-market fundamentalists opposed to government regulation have sought to create doubt in the public’s mind about the dangers of smoking, acid rain, and ozone depletion. Now they have turned those same tactics on the issue of global warming and on climate scientists, with significant success.

A prominent marine biologist says the impacts of the oil gushing into the Gulf of Mexico will persist for years, no matter when the flow finally stops. What’s more, scientist Thomas Shirley says that most of the damage remains out of sight below the surface, as creatures succumb to the toxic effects of the rapidly spreading tide of oil.

In response to the widening disaster in the Gulf of Mexico, government officials have approved a plan to intercept the oil by building a 45-mile sand berm. But scientists fear the project is a costly boondoggle that will inflict further environmental damage and do little to keep oil off the coast.

Within the planet’s oceans and soils are trillions of bacteria that store and release far more carbon dioxide than all of the Earth’s trees and plants. Now, scientists are attempting to understand how the world’s bacteria will influence — and be influenced by — a warming climate.

Environmentalist David Orr says the easy part of helping the United States live within its ecological limits may be passing laws, such as one that puts a price on carbon. The hard part, he maintains in an interview with Yale Environment 360, is changing a culture of consumption that causes extensive environmental damage — and unhappiness.

The practice of “commissioning,” in which an engineer monitors the efficiency of a building from its design through its initial operation, just may be the most effective strategy for reducing long-term energy usage, costs, and greenhouse gas emissions from buildings. So why is it so seldom used?

Is human activity altering the planet on a scale comparable to major geological events of the past? Scientists are now considering whether to officially designate a new geological epoch to reflect the changes that homo sapiens have wrought: the Anthropocene.

A battle is quietly being waged between the industry that produces genetically modified seeds and scientists trying to investigate the environmental impacts of engineered crops. Although companies such as Monsanto have recently given ground, researchers say these firms are still loath to allow independent analyses of their patented — and profitable — seeds.

The oil slick spreading across the Gulf of Mexico has shattered the notion that offshore drilling had become safe. A close look at the accident shows that lax federal oversight, complacency by BP and the other companies involved, and the complexities of drilling a mile deep all combined to create the perfect environmental storm.

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.

California’s high-tech giants have long used renewable energy to help power their Silicon Valley headquarters. Now, companies such as Google, Adobe Systems, and eBay are preparing for the next step — investing in off-site solar and wind installations and innovative technologies that will supply their offices and data centers with green electricity.

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?

With nearly $800 billion in drugs sold worldwide, pharmaceuticals are increasingly being released into the environment. The “green pharmacy” movement seeks to reduce the ecological impact of these drugs, which have caused mass bird die-offs and spawned antibiotic-resistant pathogens.

This April marks the 40th anniversary of Earth Day, an event that has attracted millions to environmental causes. But winning passage of meaningful legislation on climate change requires more than slogans and green talk — it demands intense, determined political action.