1. The legend of Dr Faustus crops up repeatedly in European literature, drama and music, suggesting that it has profound meaning. In our relationship with the biosphere we have perhaps made a Faustian bargain. In return for unrestrained use of the Earth’s resources, we may have mortgaged a long-term future. Currently we are hoping to renegotiate the bargain, but there is detail in the small-print-clauses about climate change, destruction of ecosystems and consequent release of nutrients to waterways that we have ignored. Natural biomes determine that the biosphere is maintained in a state favourable to our particular biochemistry. Part of the mechanism is regulation of atmospheric gas composition through storage of carbon as biological deposits.
2. Shallow lakes and wetlands, and the tundras and forests of wet soil, store carbon at a much greater rate than the global ocean. The influence, on shallow lake systems, of warming coupled with degrees of eutrophication has been studied in replicated experimental ponds. The first experiment used modest nutrient addition and a 3 °C rise in temperature. Such warming led to some increase in phosphorus availability, takeover by an introduced warm-water species, Lagarosiphon major of the submerged plant community, and an increase in the frequency of severe deoxygenation, with occasional fish kills.
3. The second experiment used a rise of 4 °C against a similar ambient background to that of the first experiment, but a nutrient environment much closer to that of lowland eutrophicated waters. Especially with moderate nitrogen loading, floating duckweeds became very abundant, though submerged plants persisted. Oxygen concentrations fell markedly. Final fish biomass fell by 60% on warming and 80% at the highest nutrient loading used, but the combination of warming and even modest nutrients brought oxygen frequently to zero overnight and killed all the fish. Because the fish used (Gasterosteus aculeatus) were extremely resilient, there are severe implications for many other European fish species.
4. Analysis of oxygen curves allowed calculation of metabolic parameters of the tank systems. Both warming and nutrient addition substantially increased community respiration compared with photosynthesis. Extrapolation suggests that if this phenomenon is widespread, an increase of about 1.8 Gt over the 1990’s net annual atmospheric accumulation rate of 3.2 Gt might result. Since the IPCC models of future climate change do not include such biological feedbacks, they may thus seriously underestimate the future rise in temperature and its consequences.
5. Thematic implications: we do not know if our Faustian bargain can be renegotiated; our political and social institutions are poorly equipped in knowledge and barely accept the importance of biosphere processes, and our scientific establishment is reductionist and conforms to the values of the rest of society. Current approaches to mitigation of climate change attend only to carbon release from human institutions, with little or no reference to natural systems. The future is exceptionally uncertain.