Thursday, 19 November 2009

Outsourced biodiversity

Just read (or, more accurately, skim-read) an article in Nature about Gretchen Daily and ecosystem services. She's a big advocate for the latter, and the article reviews the topic and the dollar estimates placed upon the benefits we, usually unknowingly, accrue from the Earth. An early estimate for global services was $33 trillion per year, which is not far off its economic "equivalent", Gross World Product, estimated at $41 trillion.

One of the attractions of this presentation of ecology, aside from it accurately telling us something important about the infrastructure that supports our civilisation, is that it provides a backdoor route for protecting biodiversity. By (necessarily) summarising the beneficial effects, it encourages the preservation of intact ecosystems, regardless of whether the constituent organisms are cute and cuddly or over-limbed and venomous.

However, the article goes on to make a point that's inherent in the concept of ecosystem services, but which I'd not thought much about before. Basically, what happens if your ecosystem services can be outsourced to a less biodiverse alternative? The specific example given in the article is the replacement of a complex native habitat with a "monotonous plain of non-native grass [that] delivers better and cheaper ecosystem services, measured in water filtration, carbon sequestration and flood protection".

Put this way, the concept of ecosystem services could be applied to determine the "minimum specification" ecosystem that will provide the required outputs without trimmings such as newts and nematodes. Of course, diverse natural ecosystems generally deliver more than just a couple of core services, but they also (presumably) contain redundancies in the form of species that contribute no anthropic benefits. Faced with a small number of preferred system outputs and the choice between a simple managed system, and one which includes all of nature's glory, it's easy to see how biodiversity could take a backseat.

Admittedly, the argument could be made that we don't understand ecosystems well enough to ever be faced with such a bald choices, and there's something in this. We've got a pretty good idea how the major players in ecosystems operate, but the full breadth of interactions escapes us, and there are plenty of examples from ecology of where numerically "irrelevant" species play a key role. Furthermore, even ostensibly human environments such as cities become home to a range of unanticipated species (good, bad and ugly), and any engineered ecosystem is liable to be similarly infested and affected. So, for the foreseeable future, largely intact ecosystems are likely to be cherished (in that special "marginalised unless vital" sense).

But this does makes one realise that we need more than a utilitarian argument for retaining biodiversity. That might halt the barbarians at the gate for a while, but it's not enough that our fellow non-human residents of Earth "merely" close the loops of the planet's biogeochemical cycles, we need to think beyond this. Essentially, we need to factor in a moral dimension to biodiversity, and we need to be able to sell this plausibly when the ecosystem engineers come knocking.

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