Monday, 16 February 2009

Burton's Biomass Extinction theory

Having just returned from Kenya, where the human population has pretty well doubled since I first visited, I was musing on the impact of this vast quantity of biomass.

When looking at endangered species and declining species, despite a huge number of factors being cited as direct causes or even indirect causes, one area that appears to have been generally overlooked (or at least unquantified) is the carrying capacity of habitats related to biomass. In general, any given habitat can support a certain biomass of plants and animal species. This biomass can be increased by removing predators, by introducing fertilisers, and various other methods of short-term production. Some habitats will also store biomass in the form of carbon (such as peat) but essentially most habitats probably exist in some sort of equilibrium as far as the biomass is concerned, even if there are short term fluctuations and cycles.

If any of my readers know of publications on this topic, I would welcome references. One of our recent students looked at the issue in relation to the increase in goats and cattle, and the displacement of antelope and other wildlife, but found very little published data. And since Oxfam, Christian Aid and others continue to market the idea that goats are a solution to the issues of poverty, this has direct relevance.

If we examine areas where human interventions have increased the biomass of humans, their domesticated livestock, and crops, it comes as no surprise to observe that the biomass of the species previously existing in those areas has decreased, and with the decrease in biomass, there is also a loss of diversity (the latter being the phenomenon most commonly described). However, most of this dramatic increase in biomass has only occurred in the last two centuries, and consequently the impact on species loss may not yet have had a major impact, as many species are fairly resilient. But my view is that many species, over a relatively short period of time will start to show rapid declines to the point of ecological extinction, as the simplified ecosystems created by the human-livestock-crop interrelationships, will encourage a few relics of the wild ecosystem to become dominant, with others careering towards extinction. The only way of reversing this trend is to allow the human-livestock-crop-wildlife relationship to become more complex (by encouraging more natural cropping systems, less use of pesticides and herbicides), and by reducing the overall biomass of humans and their livestock.

Compounded with the increase in the increase in human related biomass, there has also been a massive decrease in the area available for natural biomass to co-exist. Vast areas are now given over to urban developments and infrastructure, much of which involves the total replacement of natural vegetation and habitats with roads, housing and other solid materials. This is most clearly visible in a country such as England, where even once common species such as the house sparrow are declining, along with most birds found in arable farmlands. But it is also true in a country such as Kenya, where not only has the human population increased dramatically, but urban areas have spread, and the numbers of domestic livestock has increased even more dramatically than that of the human population. And at the same time, the areas available for grazing this huge biomass of domestic livestock has been significantly reduced by the spread of agriculture. This leads to overgrazing, depletion of the soils, so that agriculture becomes dependent on artificial fertilisers, in order to maintain the levels of plant biomass.

If the theory that biomass, as much as biodiversity is playing a role in the maintenance of ecosystems, then there is an even bigger catastrophe waiting in the wings, but because much of this is a very recent phenomenon - essentially post 1950 - it is too early to speculate on the scale of the extinction. However if this theory is correct, then we may be beginning to see a wave of extinctions that even the worst pessimists of the end of the 20th century couldn't have predicted.

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