ESI maps serve as quick references for oil and chemical spill responders and coastal zone managers. They contain three kinds of information: (1) Shorelines (color-coded to indicate their sensitivity to oiling); (2) Sensitive biological resources (such as seabird colonies and marine mammal hauling grounds. They are depicted by special symbols on the maps); and (3) Sensitive human-use resources (such as water intakes, marinas, and swimming beaches). Project scientists have created collections of ESI maps, called ESI atlases, for most coastal areas in the US, including Alaska, Hawaii, the Great Lakes, and the Trust Territories. Each atlas includes maps and additional data and information. Starting in 1995 with the outer coast of California, ESI project members began using a Geographic Information System (GIS) to produce updated ESI maps that are higher in quality and can be more readily reproduced.