However, other issues have arisen in the last two decades, and a reformulation of the underlying problem is now appropriate. In this century, the scarcest resources are more likely to be common property resources, such as benign and stable climate, clean air, environmental waste assimilative capacity, biodiversity, tropical forests, fisheries, and fresh water. Moreover, the pressure causing environmental degradation comes from industrial activity, land use, and especially emissions of waste residuals to air, water, and soil. The emissions, in turn, are from the end of the "life cycle" of materials previously harvested from the biosphere or extracted from the earth's crust, processed, and discarded either during the production process or after final consumption.