Harvard's experimental forest is wired up and down to study how changing conditions affect entire ecosystems.

“Everything is connected to everything else,” says the First Law of Ecology, laid down in 1971 by the U.S. biologist and activist Barry Commoner. He was addressing scientists who had been trained to manipulate a few key variables, after isolating them from all outside influences, to see their effects on a few outcomes. But in ecology, everything varies together; an interwoven web links microbes to mountains.

Even a single forest has enough entwined connections to boggle the mind. Tree growth depends on fleeting changes in the atmosphere, soil, and water. The arrival of new plant and animal species, or the disappearance of old ones, might spell disaster now or a bloom some years hence. Even the tiniest microorganisms can shape the fate of towering oaks.

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