Environmental Stress

Abstract

Natural environments cause stress to the organisms which inhabit them. For example, on a rocky shore, tidal movements cover and uncover the denizens twice daily, to a greater or lesser extent, depending upon the phase of the cycle of spring and neap tides. During exposure, perhaps for several hours according to their vertical position on the shore, organisms may be subjected to the withering heat of a summer noonday sun or the more subtle stress of freshwater from a rainstorm. With each returning tide the surge of the waves grinds or batters the animals and plants clinging to the exposed rock surfaces while with each retreat shear forces would rapidly wrench them away were they not so pliant, so well cemented or equipped with powerful suckers. One has only to walk the high-tide mark after a violent storm to see how precarious is continued survival on a rocky shore. In terrestrial environments stresses are generated by high winds, low and high rainfall, frost action, snowfall and intense sunshine. Even the constant pull of gravity generates stress, as is evident when climbing plants fail to find support or fully-laden branches of fruit trees give way under the strain.