Sunday is Earth Day. And while we recommend you spend at least part of it outdoors, we also think you should check out these four FRONTLINE films on the environment. Watch them below; visit their websites for interviews, maps and so much more; and then take a look at some of our other favorite projects on the environment that we’ve linked to at the bottom of this post.

Heat

A global investigation into one of the greatest crises that mankind has ever faced — can we roll back global warming?

Poisoned Waters

A far-reaching investigation into America’s great waterways. They are in peril. There’s a new wave of pollution that’s killing fish, causing mutations in frogs — and threatening human health.

Nuclear Aftershocks

FRONTLINE travels to three continents to explore the debate about nuclear power: Is it safe? What are the alternatives?

The Spill

An investigation into the trail of problems — deadly accidents, disastrous spills, countless safety violations — which long troubled the oil giant, BP. Could the disaster in the Gulf of Mexico have been prevented?

For a more on the history of April 22, take a look at AMERICAN EXPERIENCE’s fantastic film Earth Days. And our friends over at FRONTLINE/World put together Carbon Watch, a multimedia investigation into the currencies of global warming.