ABSTRACT
Human beings are part of the biosphere. In most parts of the world, humans are the dominant organism. The previous chapters have shown that we share the biosphere with millions of other species. We also depend, as much as any other living creature, on the functioning of ecosystems in the biosphere to support our existence. People, unlike all other species, have the unique ability to affect profoundly the nature and functioning of ecosystems throughout the biosphere. This chapter is concerned with anthropogenic effects on ecosystems. In some ways humans can be considered as simply another biological species, albeit one that exists in very large numbers and which is capable of the most profound ecological and environmental impacts. Although this has a biological logic, the scale and importance of human impacts, together with the fact that, not unreasonably, humans tend to view the world from a human perspective, makes the separation of human roles in ecosystems from that of other species generally a more realistic approach. There are now about 6,000 million individual Homo sapiens. This large population affects ecosystems, through elimination of species, modification of flows of energy or nutrients or by change to the abiotic environmental component of ecosystems; it not only affects all other species with which we share the biosphere, but also threatens the support systems for all of life on earth.
