Sunday, January 20, 2008
Top of the Chain
What happens when a species at the top of the food chain disappears? If one species of whale, say a species with a relatively small population, were to go extincet, what would be the consequences?
I suspect many, if not most, people would guess that the rest of the food chain, on which the top species was perched, would simply flourish, and that any follow-on effects would be minimal or none.
While it is true that species directly below likely will increase their numbers, a chain of changes will inevitably follow. Rather than speculate about the disappearance of a species of whale, the polar bear or other species at risk, a look at a species that was eradicated from a confined area can serve as a good example.
Wolf eradication in Yellowstone (and surrounding areas) came as a result of ranchers who blamed wolves for excessively preying on their cattle. What the exact number of losses were is probably not truly known, but what is known is that wolf predation on commercial livestock was largely a result of the elimination of bison (buffalo) herds, a primary food source for wolves. At the time, however, hard science, even if it were available, didn't matter. The wolf had been made an object of fear and hatred, to the benefit of a particular economic interest.
With the removal of the grey wolf population, however, the elk population, having also been an important food source to wolves, increased dramatically. The increased elk herds overgrazed various species of vegetation, including pine trees. The loss of enough pine and other vegetation resulted in soil erosion, loss of ground cover for other species, and the loss of food for still more species.
The soil erosion was significant enough to cause flooding problems, further disturbing the ecosystem.
Whatever one thinks might be the specific effects of ecosystem disturbance or change, no matter how refined one's modeling, there are always at least a few unanticipated results. Ecologists are paid to understand ecosystems and provide at least guidance, if not accurate and specific predictions of ecological change. Given that there is no such thing as 100% accuracy, the combination of uncertainty and the lack of immediate consequences presents a danger to public policy making and societal knowledge of ecological issues. This is especially true with matters of global scale. As humans, we focus on our immediate surroundings and what we can see now.
Lake Superior -- Top of a Chain
The example of wolves in Yellowstone is a relatively simple example of how changes precipitate unintended and unwanted consequences. The same principle obviously applies to geologic systems. The sheer size and power of Lake Superior deceives most into believing it is immutable -- that it cannot be moved, cannot be adversely affected by anything but events of a nuclear scale.
I think most people experience Superior through something akin to a drive-by shooting "Stop here! That's a great picture!". So 99% of its visitors are probably caught in the spell of magnitude and beauty. Absolutely this is essential to understanding our planet, our home.
Three times in my life, out of four trips to Superior, I have been able to stop and live for a bit on the shore. These times have not been simply pleasant vacations, but have been "incrementally" transformative, if that makes any sense.
This last trip was a bit longer. Perhaps not long enough in an absolute sense (permanent residence would be appropriate), but long enough to calm my soul while opening it to "small" things that open up a world not often noticed, hidden behind size and power.
The image that best illustrates this, I think, is this photo of moss & cedars growing from pre-Cambrian rockface of the shore. The whole concept of organisms that break down rock -- and granite at that -- has always amazed me. The conversion to soil as a result of whatever chemical action that is employed is remarkable. In this case, it challenges one to consider that the "food chain" is actually inverted. We would normally consider granite one of the most permanent features of this ecosystem, yet it is lowly moss & lichen that reign. Without species that can convert ancient rock to soil, other species such as the cedars cannot survive.
I am not a working biologist, even though my undergraduate degree is in Biology with an emphasis on invertebrate zoology and my strongest interest continues to be aquatic ecosystems. I am sure that I have oversimplified things with this example. So I admit to being a bit of a wannabe, despite my original grounding in the sciences, and I do welcome comments, corrections and any additional input.
Despite feeling that I have missed something important by not having pursued a work career in my field of study, I am encouraged that I can choose to "reclaim" that study as a foundation for the finale of my life, and combine a renewed interest with my experience and vision in photography and my love of the water.