Every extra human means fewer animals

8 02 2010

© The Sun

As promised some time ago when I blogged about the imminent release of the book Conservation Biology for All (edited by Navjot Sodhi and Paul Ehrlich), I am now posting a few titbits from the book.

Today’s post is a blurb from Paul Ehrlich on the human population problem for conservation of biodiversity.

The size of the human population is approaching 7 billion people, and its most fundamental connection with conservation is simple: people compete with other animals., which unlike green plants cannot make their own food. At present Homo sapiens uses, coopts, or destroys close to half of all the food available to the rest of the animal kingdom. That means that, in essence, every human being added to the population means fewer individuals can be supported in the remaining fauna.

But human population growth does much more than simply cause a proportional decline in animal biodiversity – since as you know, we degrade nature in many ways besides competing with animals for food. Each additional person will have a disproportionate negative impact on biodiversity in general. The first farmers started farming the richest soils they could find and utilised the richest and most accessible resources first (Ehrlich & Ehrlich 2005). Now much of the soil that people first farmed has been eroded away or paved over, and agriculturalists increasingly are forced to turn to marginal land to grow more food.

Equally, deeper and poorer ore deposits must be mined and smelted today, water and petroleum must come from lower quality resources, deeper wells, or (for oil) from deep beneath the ocean and must be transported over longer distances, all at ever-greater environmental cost [my addition – this is exactly why we need to embrace the cheap, safe and carbon-free energy provided by nuclear energy].

The tasks of conservation biologists are made more difficult by human population growth, as is readily seen in the I=PAT equation (Holdren & Ehrlich 1974; Ehrlich & Ehrlich 1981). Impact (I) on biodiversity is not only a result of population size (P), but of that size multiplied by affluence (A) measured as per capita consumption, and that product multiplied by another factor (T), which summarises the technologies  and socio-political-economic arrangements to service that consumption. More people surrounding a rainforest reserve in a poor nation often means more individuals invading the reserve to gather firewood or bush meat. More poeple in a rich country may mean more off-road vehicles (ORVs) assulting the biota – especially if the ORV manufacturers are politically powerful and can succesfully fight bans on their use. As poor countries’ populations grow and segments of them become more affluent, demand rises for meat and automobiles, with domesticated animals competing with or devouring native biota, cars causing all sorts of assults on biodiversity, and both adding to climate disruption. Globally, as a growing population demands greater quantities of plastics, industrial chemicals, pesticides, fertilisers, cosmetics, and medicines, the toxification of the planet escalates, bringing frightening problems for organisms ranging from polar bears to frogs (to say nothing of people!).

In sum, population growth (along with escalating consumption and the use of environmentally malign technologies) is a major driver of the ongoing destruction of populations, species, and communities that is a salient feature of the Anthropocene. Humanity , as the dominant animal (Ehrlich & Ehrlich 2008), simply out competes other animals for the planet’s productivity, and often both plants and animals for its freshwater. While dealing with more limited problems, it therefore behoves every conservation biologist to put part of her time into restraining those drivers, including working to humanely lower [sic] birth rates until population growth stops and begins a slow decline twoard a sustainable size (Daily et al. 1994).

Incidentally, Paul Ehrlich is travelling to Adelaide this year (November 2010) for some high-profile talks and meetings. Stay tuned for coverage of the events.

CJA Bradshaw

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