Natural Reverse Desertification

Response to a question...
"Anonymous said...
How does nature reverse desertification?

We know that drought, climate change, overgrazing, and deforestation can cause desertification, and we know that certain careful agricultural practices (nitrogen fixation in the soil, introduction of microbial life, planting seeds, irrigation) can reverse it. But if desertification happens naturally on a large scale, as can be witnessed in the Sahara and Gobi Deserts (not all of the current effects can be considered to be anthropogenic), then there must be natural mechanisms to reverse desertification, otherwise after millions of years the entire earth would be desert.

October 7, 2008 2:01 PM"

Here's the answer as best as I can tell... I'll warn my readers that it sounds like I'm oversimplifying a complex topic, but I feel concision is a strength and not a weakness.

So the answer is... Climate and humidity. Deserts are created in the natural sense because of a lack of humidity (or rather, a desert is the lack of humidity). I guess that depends on who you ask. But as for why the earth isn't one big desert, is simple. Just as climate changes can decrease humidity in some regions, it can cause increased humidity in other regions. This increased humidity can come from many different reasons, changes in wind currents, changes in ocean currents, overall climate changes, etc.

It is worth noting that we are not moving in the right direction of climate change to encourage reverse desertification. The largest factor in creating deserts is temperature. Heat causes humidity to rise out of the soil. That being said, we are on a path to more deserts, and less vegetation. This little thing called "global warming" can be blamed for that. However, that's a topic onto it's own.