Five stunningly large forests remain on Earth: the Taiga, extending from the Pacific Ocean across all of Russia and far-northern Europe; the North American boreal, ranging from Alaska’s Bering seacoast to Canada’s Atlantic shore; the Amazon, covering almost the entirety of South America’s bulge; the Congo, occupying parts of six nations in Africa’s wet equatorial middle; and the island forest of New Guinea, twice the size of California. These megaforests are vital to preserving global biodiversity, thousands of cultures, and a stable climate, as economist John W. Reid and celebrated biologist Thomas E. Lovejoy argue convincingly in Ever Green (W. W. Norton). Megaforests serve an essential role in decarbonizing the atmosphere — the boreal alone holds 1.8 trillion metric tons of carbon in its deep…