IT HAS BECOME COMMONPLACE to remark that humans are now the dominant environmental force on the Earth. The indications are strong and diverse. They range from paleontologists reaching a consensus that humans contributed to megafaunal extinctions on at least two continents, North America and Australia;1 recognition that formerly intact marine ecosystems have changed enormously;2 suggestions that climate has changed sufficiently that no ecosystem is immune from alterations in species composition;3 remarks that pollution is widespread even in Antarctica;4 and arguments that human predation on mammals is pernicious and the principal driver of changes in phenotypic traits of exploited species in many areas.5 Some scientists use geographic data to show that human activities affect almost every terrestrial system (e.g., the human footprint6). Indeed, the current epoch is now being referred to as “the Anthropocene,”7 which has led geologists to formally debate stratigraphic evidence for this new phenomenon and to argue over not if but when it began.8 With the catchword Anthropocene in ascendancy, one might easily come away with the impression that nowhere on Earth is natural, in one of the word’s specific meanings of ecosystems being untouched by humans,9 and indeed it is common to hear the phrase “humans have altered everything.”