The publication The Great Barrier Beach Field Guide is the result of several years of beach surveys of the Northeast Coast, Long Island, New York, New Jersey, New England, and the coastline of North and South Carolina. In its natural state, the barrier beach is a fascinating mixture of opposites: high and low elevations, wet and dry, hot and cold, sterile and fertile, windblown and sheltered. It is the combination of these factors that, with a strip of land varying in width from a few thousand feet to a few hundred or less, have produced several distinct zones of flora distribution. Considering the mixture of abiotic elements of the various zones, the flora that occupy a zone must be genetically equipped to adapt or be replaced by a genetically equipped species. The environment is the selecting agent; it determines and selects the most genetically equipped to survive and perpetuate.