The Unifying Theme of Our Chaning Planet centers on the basic metabolism of the interactive and integrated ecosphere of planet Earth and how it has changed over time, how it has been influenced by the circulation of numerous natural substances flowing through its atmosphere, land, water, and sea, and how humankind has become a geologic force in the ecosphere. The book discusses various aspects of both natural and human-induced global environmental change, emphasizing the historical (geologic) perspective of processes and changes in the lithosphere, atmosphere, hydrosphere, and biosphere systems through time, and human influences on the systems. It demonstrates how population growth, affluence, resource consumption, and technology give rise to human activities that lead to the environmental problems of rampant deforestation and conversion of forests to urban, grazing, and farm lands with major effects on the environment and people; extensive modifications of terrestrial and aquatic systems and their degradation, including stresses on freshwater resources and cultural eutrophication; anthropogenic sulffur and nitrogen emissions to the atmosphere that increase the acidity of rainfall and freshwater aquatic systems with damaging effects on the biota; photo-chemical smog, including formation and spread of tropospheric ozone and the health issues associated with smog; stratospheric ozone depletion and the "hole in the sky" and its effect on climate and the ultraviolet flux; and the currently most talk-about and debated issue of environmental change, that of the enhanced greenhouse effect and global warming with its effects on patterns of precipitation, soil moisture and crops, geographical distribution of vegetation and plants and animals, freshwater runoff, sea-level rise, photosynthesis and respiration on land and in the sea and the uptake of atmospheric CO2, circulation of the ocean, and ocean acidification. The book is a holistic treatment of both natural and human-induced change from the beginning of the Earth on into its future.