bridges vol. 15, September 2007 / Feature Article
by Helmut Haberl
Fuels derived from biomass are increasingly seen as a suitable option for reducing society's dependence on imported, exhaustible energy sources such as fossil fuels and for mitigating global warming. Biomass - both plant and animal biomass - is ultimately derived from the organic materials synthesized by green plants from inorganic components in the process of photosynthesis. Biomass contains energy-rich substances that may be seen as "stored solar energy." Humans vitally depend on biomass to feed themselves and their domesticated animals, as raw material for many products and, increasingly, as a source of energy.
However, biomass is not only important for humans. The energy supply of ecosystems also derives from the energy fixed by green plants in photosynthesis. All the intricate food webs that underlie the complex patterns and processes in ecosystems originate in the process of net primary production (NPP), i.e., the production of biomass by green plants through photosynthesis. As humans expand their utilization of that vital resource, they inevitably reduce the amount left over for all other species - a process summarized by the phrase "human appropriation of net primary production" or HANPP.
This article discusses some implications of a study recently conducted by my colleagues and myself on the impacts of our species on the earth's ecosystems. Some of these results were recently published in the Proceedings of the National Academy of Sciences of the USA (http://www.pnas.org/cgi/content/abstract/0704243104v1 , Haberl et al., 2007).
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