05 October 2010

Ecosystem Engineers

I know, I'm not supposed to be posting or even going on blogspot this month. But there was a guest lecturer today in bio who has forced me to sidetrack from studying just for today. Plus maybe if I blog about what I learn at varsity, it counts as studying?

If you look up ecological/ecosystem engineering on google, you'll mostly find links on a discipline of engineering which focuses on mimicking natural systems, things like bioremediation. While this is a really interesting area, which I'm so glad is becoming more and more prominent and even being taught as a course in universities - it's not the kind of engineering I'm talking about. I want to put his whole lecture into a little ecology nutshell and then use it to fill a hole in one of my own theories.

Ecosystem engineers are:
“organisms that directly or indirectly modulate the availability of resources(other than themselves) to other species by causing state changes in biotic or abiotic materials. In so doing they modify, maintain and/or create habitats
You get two types of ecosystem engineers: allogenic engineers and autogenic engineers.

An allogenic engineer modifies its environment with the structures it builds. Some examples: a beaver and its dams, termites, ants and other social insects with their nests/mounds and corals forming reefs. Here's a picture of one of the largest beaver dams in North America, almost a kilometre wide, you can see the blatant effect it has on the environment:

An autogenic engineer modifies its environment by modifying itself or simply by being. Examples: elephants and their effect on vegetation, trees, plankton and algae. Rainforests, being the lungs of the earth, are an obvious ecosystem engineer:



You could technically think of ecosystem engineers as keystone species of sorts. Maybe think of it this way - all ecosystem engineers are keystone species but all keystone species are not ecosystem engineers. The reason for this is that often, keystone species are determined on the basis of their place in food chains and their effects on these trophic systems. Ecosystem engineering doesn't include trophic interactions.

Back to ecosystem engineers and their role in natural systems, it generally goes a little like this: Ecosystem engineer ---> acts on and alters the abiotic environment ---> in turn affects other organisms and the abiotic/biotic processes of the environment. Sometimes the engineer can set off a chain of effects that turns into a feedback loop.

Humans are an obvious allogenic engineer. And this is where that hole in my arguments comes in. I've always argued the view that while humans are a part of nature, we've gotten to the point where we've spiraled out of control into an almost separate force of nature, like there's Gaia on one side and Homo sapiens on the other, just fighting each other. Of course, if we've evolved to become the most intelligent species, it's expected that we would also be significant ecosystem engineers. One of the characteristics of an ecosystem engineer is that in order for it to have an effect on the environment, the changes it causes must be larger than those caused by local physical processes. So from now on, rather than calling human beings "a separate force of nature", which often gets me into a lot of trouble, I'll say this - we're the ultimate ecosystem engineers and we're exploiting that role.

Anyway, maybe that little bit about humans wasn't necessary, but it's shed light on my view of our species now :) All that aside, ecosystem engineering is fascinating :) Especially the research this lecturer has been involved in...just tried to google it and discovered he authored the first and most famous insect field guide in South Africa, the same one that's next on my list of field guides to buy. I love UCT :)


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