Human appropriation of net primary production (HANPP), the aggregate impact of land use on biomass available each year in ecosystems, is a prominent measure of the human domination of the biosphere. We present a comprehensive assessment of global HANPP based on vegetation modeling, agricultural and forestry statistics, and geographical information systems data on land use, land cover, and soil degradation that localizes human impact on ecosystems. We found an aggregate global HANPP value of 15.6 Pg C/yr or 23.8% of potential net primary productivity, of which 53% was contributed by harvest, 40% by land-use-induced productivity changes, and 7% by human-induced fires. This is a remarkable impact on the biosphere caused by just one species. We present maps quantifying human-induced changes in trophic energy flows in ecosystems that illustrate spatial patterns in the human domination of ecosystems, thus emphasizing land use as a pervasive factor of global importance. Land use transforms earth's terrestrial surface, resulting in changes in biogeochemical cycles and in the ability of ecosystems to deliver services critical to human well being. The results suggest that large-scale schemes to substitute biomass for fossil fuels should be viewed cautiously because massive additional pressures on ecosystems might result from increased biomass harvest.
http://www.pnas.org/content/104/31/12942.abstract
In other words, one form of human society (globalized consumerism) appropriates close to one quarter of all life on Earth - and growing. Clearly no sustainable, but hard to say what level of appropriation would be.
HANPP can be said to consist of two main factors, population number and consumption per capita, but this gets easily misleading. When talking about the population side of the equation, the usual reaction is to talk about need to limit population "elsewhere", e.g. in Africa and other places where population growth is still strong. Which of course would not affect anything in regards of HANPP, given that an African consumes only a tiny fraction of what an American consumes:
Roughly calculating, if global consumerism appropriates a quarter of life on Earth, then Americans alone, less than five percent of population, appropriate quarter of that, about 6% of all life on Earth.
If limiting population was the right and only answer, the logical thing would be to exterminate the parts of the population that consume the most, so that the "meek would inherit the world" after eating the rich. Well, not likely to happen, since the global elite of greediest lunatics (Americans etc.) are not only willing but also able to exterminate great numbers of those that consume the least, in order to keep on consuming as much as they can appropriate for themselves and then some.
All the talk about population numbers rarely consist of anything else but the greediest bastards blaming rest of humanity (that they oppress) for their own sins in fear of loosing their priviledges. Yada yada and boohoo.
