CSB #6: We're Hurting our Clean-up System

We knew that more diverse streams and rivers are less polluted. What we didn't know, though, is why. The answer goes back again to Darwin's famous theory, and one point in particular. Darwin stated that, because every organism is unique, it has its own distinct habitat or "niche." In a river, there are different habitats depending on the water's speed and factors like ripples, pools, and eddies. If there are more species living in the river, they cover more "niches," and therefore can clean more of the river.

Specifically, Bradley Cardinale of the University of Michigan was testing how efficiently algae can remove nitrate, a common chemical in fertilizers, from the water. He used over 150 model streams, looking at a single habitat in one model and multiple habitats in another. Cardinale found that the more species of algae he put into the model stream, the more efficient the water filtration became. The 8-species mix, the one with the most species of algae and diatoms (small algae-like creatures) filtered nitrate 4.5 times faster than any single species. His main object in the experiment was to demonstrate that niches are responsible for the greater efficiency in water filtration that biodiversity presents to streams and rivers. To remove all doubt, he checked different numbers and combinations of algae species in a model stream with just one habitat; here, there was no advantage. This proved that more species "filled" more niches, and filtered more nitrate out of the water.

I love how evolution connects so many different issues. Here, though, it isn't just about evolution, although the niches are certainly vital to understanding why biodiversity is essential. Diverse species can clean up the mess we make by filtering nitrate and other chemicals out of the water, but how long can the diversity remain? Many species are going extinct because they have lost their habitat, are being hunted, cannot find food, or are overridden by species that have been introduced to the environment. However, without the diverse species, the water would be much more polluted and pose greater problems for humans. Basically, by not watching out for how what we do affects other species, we are moving towards another environmental difficulty, a greater number of over-polluted rivers. It's clear that humans have to start consciously trying to preserve biodiversity.

Why don't we already preserve biodiversity because of its other advantages? I'm sure that people already try, but not enough people are trying or their efforts are not sufficient. Using fewer resources, thereby saving habitats, would help some species survive. Polluting less by using clean energy or driving less or buying local goods to decrease pollution created by shipping would help. In effect, the same things that would help solve other environmental issues. Funny, isn't it, how they're so interconnected? Anyway, biodiversity is good for cleaner water, but we need to keep our clean-up system in good condition.

Resources:

University of Michigan. "Biodiversity Improves Water Quality in Streams Through
a Division of Labor." ScienceDaily. N.p., 6 Apr. 2011. Web. 6 Apr. 2011.

The picture is from the article and is of algae species that might be found in a stream.