The conversion of forests to farmland is recognized as a major contributor to rising levels of greenhouse gases. And yet it hasn’t been clear how to best minimize the loss of sequestered carbon into the atmosphere. Is it better to maximize farm yields so as to use less land area over all? Or should farms be operated so as to retain more carbon on site, even at the expense of crop yields? Researchers reporting in Current Biology on July 26 say that, based on their extensive studies of agricultural operations in the humid tropics of Ghana, the dry tropical forest in Mexico, and temperate wetlands and forests in Poland, the best course in all cases is to limit the conversion of natural habitat to farmland, a strategy known as land sparing. That means maximizing yields on existing agricultural lands.