The term “biodiversity” refers to the variety of life on the planet—extending in scale from genes to species to ecosystems. Our understanding of biodiversity conservation, however, faces a twofold knowledge gap. First, we have no complete list of the components of biodiversity at the different levels, and second, it is difficult to judge what their values might be in the future. Therefore a core strategy for biodiversity conservation is to estimate patterns of variation, and then try to conserve as much of that variation as possible, so as to retain the full range of possible future values.