February 28, 2010

Life System Proxies: Top Predator Health

All ecosystems include food webs, and many of those webs contain a predator this is a dominant member.  Early conceptualizations of predator / prey relations characterized the system as a chain with bigger things eating smaller things in a more or less linear relationship.  We now know that the image of a chain is too simple as many species are prey in multiple food relationships and similarly those same species may eat across several of what we formerly referred to as chains.

But I digress.  The point is that in these eat and be eaten systems, be they chains or webs, there are a species that pretty much only eat.  These are things like bears, wolves, and sharks that for all intents and purposes are not normally food for other species, but do eat a lot themselves.  This species is called the top predator.

As we have learned more about how food webs work, we have learned that the presence or absence of a top predator can have a big effect on the functioning of the food system and the related ecosystem as a whole.  Sever over-fishing of northwest Atlantic cod and related predators has left huge swaths of the northwest atlantic habitat without a top predator.  As a result the food web in those areas has shifted to a very different configuration and it is not clear that the system that supported the cod will be able to re-emerge simply with simply the reduction of the fishing pressure.

So presence, absence, or change in the top predator in a food web can tell us things about how that food web and its associate ecosystem are functioning or may be changing.  Following on this a strategy that monitors the health and resilience of top predators might serve as a proxy for the health and resilience of the larger systems that those beings are part of.