Reef-building corals are increasingly exposed to warming ocean temperatures. Their immediate response to this rise in temperature is to expel their symbiotic algae and turn white, or bleach. It is mainly for these reasons that corals have been perceived by scientists as both a sign and a measure of the imminent catastrophe facing life in the oceans and, subsequently, on earth. To measure coral decline across space and time, coral scientists have come up with maps, indexes, and color-coded representations. Yet they soon realized that what they regard as today's healthy reef is, in fact, yesterday's depleted reef. This problem, referred to as the shifting baselines syndrome, renders most comparisons across time difficult and frustrates the ability to predict the future. The problem is exacerbated in the context of oceans, and further yet in the context of coral reefs, because of the lack of reliable historical records. In fact, many of the coral scientists I have interviewed perceive shifting baselines as one of the key challenges facing coral conservation scientists and managers in their attempts to accurately calculate coral decline-a project that is typically deemed necessary for effective management policies and restoration practices. My article will critically explore the application of, and the assumptions behind, the shifting baselines concept in the context of reef coral science. Specifically, I will draw on interviews with coral scientists to describe the practices and devices embedded in the creation of baselines for corals and, finally, I will explore how certain scientists are challenging the conceptions of nature and time that underlie their operations.
