What’s left after humans are gone?

Based on the most popular special in the history of The History Channel, “Life After People” (9 p.m., History) will spend 10 episodes speculating about the fate of the Earth after humans leave the scene. Experts will opine about the future disposition of our remains after some possible mass extinction. Others will predict just how long it will take man-made systems, cities and structures to disintegrate or blend into the flora and fauna. And just to rub in the point further, special effects will show what famous icons from the Chrysler Building to the Sistine Chapel will look after a few months or years without upkeep.

Episode 1 will explore the fate of 6 billion dead human bodies. Not even Glenn Beck has taken his dark “possible” scenarios to this extreme! Next Tuesday, we learn about the fate of our pets and livestock.

• Speaking of a world with limited human contact, the 2009 Interactive Achievement Award (7 p.m., IFC) honors the year’s best games, computer games, online entertainment, outstanding individuals and groundbreaking development teams. This is considered the Oscars of video games.

• A two-hour “Frontline” (8 p.m., PBS, check local listings) looks at “Poisoned Waters” and uses the Puget Sound and the Chesapeake Bay as two examples of ecosystems on the verge of collapse. Along the way, we get a survey history of the environmental movement.

By the 1960s, environmental dangers were obvious and apparent. Many lakes and rivers were dead, and some were catching fire. Smokestacks belched dark clouds, and the air killed 20 people in a Pennsylvania town in a single weekend. You could see the sewage and chemical waste pouring into rivers and streams.

When the first Earth Day happened in 1970, more than 20 million people participated — 10 percent of the population. While not entirely thrilled about the idea, then-president Richard Nixon recognized a political movement when he saw one, and he signed the Clean Water Act and created the Environmental Protection Agency, which used fines and regulation to go after industrial polluters.

In more recent decades, a pro-business political movement has made environmentalism a dirty word and has left huge industries unregulated. “Frontline” makes a strong case that a hands-off pollution policy is neither smart for business nor good for the environment.

• Contestants on “The Phone” (9 p.m., MTV) answer a telephone summons to drop everything and compete in a globe-trotting adventure.

Tonight’s other highlights

• After last week’s “save,” singers compete on “American Idol” (7 p.m., Fox) with the knowledge that two will be eliminated on Wednesday.

• Confusion follows after a sudden suicide in Grand Central on “Fringe” (8 p.m., Fox).

• A storm threatens on “Deadliest Catch” (8 p.m., Discovery).

• “Eco Trip” (8 p.m., Sundance) offers viewers a guilt trip about the environmental impact of ordinary products.

• Trevor tries to fix up an ex-con with his parole officer on “Cupid” (9 p.m., ABC).

• Tommy’s sponsor worries about him on “Rescue Me” (9 p.m., FX).

• Murder stalks the museum world on “The Mentalist” (9 p.m., CBS).