Thursday, November 27, 2008

My two cents about freshwater ecology

Cows in a river is not a good things for many reasons. First or all, it makes the Fisi Camp luxury bath a little less luxurious when you see a cow upstream of you relieving itself. More importantly though, cows can have a detrimental effect on the ecology of the river and the park.

The first picture below shows cow grazing on the eroded banks of the Talek River. The banks of this river are heavily eroded because during periods of heavy rain, the river rises quickly and the swift current washes much the bank downstream. The erosion is exacerbated by the fact there is very little plant growth on the banks. Plant roots help to hold the soil in place reducing erosion. Plants, trees in particular, also soak up a large amount of water, making the current flow less swiftly and reducing the volume moving downstream. The extra silt in the river from erosion, which gives the river its brown color also blocks sunlight from reaching freshwater plants growning on the bottom of the river. When allowed to grow, these plants produce oxygen for animals in the river and help keep the river bed from washing away.

A second major problem with cows in the river is nutrient loading. When cows excrete urine and feces into the river, it adds nutrients to the system. These nutrients are usually gobbled up quickly by algae and bacteria, producing a green layer on top of the water areas where the water is slow moving. The algae and bacteria can reproduce so quickly that they may use up all of the oxygen in the water, leaving fish and invertebrates to suffocate. This is a common cause of fish kills. I have not observed this yet in the Talek River, as rivers can usually maintain a high enough oxygen level so this does not happen, but in ponds or slow moving water it can be a real problem.

If that wasn't enough, how am I supposed to get so fresh and so clean with brown/green water? To be fair, my bathing in the river is not good for the river, but at least I am not grazing on the banks too.

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