Anthropogenic Modification of Land, Coastal, and Atmospheric Systems as Threats to the Functioning of the Earth System

Over the past two centuries, the tremendous growth of the human population and the high resource demand of technologically developed societies has made humanity a geochemical and geophysical force that is able to compete with Nature's forces and to threaten Earth system functioning. Human activities are changing the composition of biosphere, atmosphere, and hydrosphere, affecting global climate, and may even perturb the main circulation patterns of the world's oceans. Human impact on the Earth system is illustrated by examining the effects of intensive agriculture, tropical deforestation, and excessive nutrient inputs into coastal ecosystems. Because of the numerous feedbacks and teleconnections in the Earth system, the change resulting from such perturbations is likely to be nonlinear and contain abrupt discontinuities. In this situation, the prudent course would be to maintain the Earth system as much as possible within the known parameter space and to pursue a course of sustainability using the knowledge gained from Earth system research.