A frog the size of a fingernail. A poncho-clad farmer leading his mule. A tree, some intertwining leaves, a silhouetted figure holding a pot. Such logos are stamped on labels of coffee, cocoa, mangoes, jeans, and myriad other products, certifying that the object for sale is in some way “sustainable”—made, in other words, in a way that meets humanity’s needs without jeopardizing the ability of future generations to meet their own.

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