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Too Wet!

January 9, 2015

A surprising limiting factor in some parts of the desert is too much moisture.

Wait, you say, I thought deserts were too dry?

Because there’s usually so little rain, nobody is really prepared for much. So even what might be considered a light rain elsewhere can be enough to flood out desert burrows, nests, hollows, and lowlands. If you are a creature who can move fast, or a plant that can hold its breath, you will get through it.

But even in the desert, rain is not always light. During the summer monsoon months, and a few other times of year, there can be heavy downpours.

And adding to the effect, there’s that old caliche we talked about before. This is the impervious layer of minerals and clay that forms over time a short distance down under the desert surface, and acts as a water-trap. The water can’t sink in–so where it can, it slides off downhill.

With a light rain, you can suddenly get a flash flood. With a heavy, or extended rain, you can get massive dangerous flooding, the kind that kills animals, large as well as small, and washes away trees and cars and buildings.

In the middle of many human habitations in the desert, you will find long empty wild spaces, often called “washes.” These are where the flash floods wash through, carrying away whatever is in their path.

It’s strange, when you think about it, how moisture could be a problem, and a limiting factor, in both directions in the desert.

Or maybe not. Because a lot of living things want conditions that are not too much, or too little. Instead, they want things to be generally within an agreeable range. So when you look at a limiting factor, it can be fun to check if there is another one lurking at the opposite side. Yet another mystery.

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