Thomas E. Lovejoy a pioneer in the use of economics to conserve forests and other ecosystems globally is joined by John Reid, who has worked in the Amazon since 1965, in presenting a case for:

How Big Forests Solve Global Problems

Sit on a log by the Madidi River in Bolivia at dusk and you can hear what an Amazon forest should sound like. The music includes red howler monkeys, breathy thumps from the mutum jungle fowl, droning cicadas, eerie calls locals attribute to deadly bushmaster vipers and the unhinged excitement of elusive titi monkeys. Around your feet, the beach is crisscrossed by jaguar tracks and those of the pony-size tapir, a shy beast that, if you keep quiet, will saunter out of the forest and swim across the river.

This is what scientists call an “intact forest landscape.” It’s a swath of at least 500 square kilometers (about…