Reversing Desertification

Desertification is the process in which arid grasslands are transformed into desert through overgrazing and drought. Although overlooked at times desertification is a major world issue as it currently affects about 25% of the total land on Earth and over 250 million people (Allington and Valone 2010). The primary factor contributing to desertification is the overgrazing of land by livestock. Several studies have shown that vegetation decreases soil erosion while increasing the rate at which water is absorbed. A widely shared belief is that the process of desertification is irreversible, meaning the only the only way to stop desertification is to prevent it from starting in the first place. When vegetation is removed through overgrazing soil erosion increases which in turn prevents any further growth of vegetation, supporting this theory. However, new evidence has been discovered that suggests this information is not entirely true.

A recent study conducted in 2007 by G.R.H. Allington and T.J. Valone has reported recovery from desertification at 4 different locations providing scientists with reason to believe that the effects of desertification can in fact be reversed. Allington and Valone used a site in the Chihuahuan Desert in south-eastern Arizona that had once been arid grasslands to conduct their study. The site underwent desertification in the early 1900's due to drought and overgrazing but was fenced off in 1958 to prevent any further damaged. After 40 years of being undisturbed Allington and Valone observed the growth of tall grasses inside the fence that were more than four times the height of those outside (Allington and Valone). The data they collected also showed that water infiltration rates were 24% higher inside the fence and there was an increase in soil nutrients levels.

The results of this study proved three main points:

1. The growth of perennial grasses was less noticeable underneath shrubs, which means shrubs may prevent the recovery of grasses in desert regions.
2. Reversing the effects of desertification leads to an increase in soil quality, which in turn promotes further growth of vegetation.
3. The soil inside the fence gradually became less compact in the absence of livestock. This allowed for higher water infiltration rates, causing more vegetation to grow.

The main challenge presented by desertification is preventing deserts from spreading even further. There are several methods that can be used to prevent the spread of deserts, all of which are not entirely effective. If a solution is not found soon arid land will continue to be degraded, creating huge issue for the economy as potential farmland and homes are lost. More money is also put into slowing desertification down but not actually finding a solution. Both Allington and Valone suggest that future restoration attempts take into account this method of reversing desertification.

The authors of the study published indicate that there were four sites located around the world from which they have recorded similar results but they have only shown the data collected from one site. The issue with this experimental design is the lack of data they have provided the reader with. The experiment would appear to be bias and misleading because their final result was reached after only one test. Collecting data from the other three sites would need to be collected in order to determine whether or not the first result was not just a fluke. The authors excuse this error in saying "our work is the first to examine and demonstrate differences in soil physical and chemical properties at a desertified site experiencing perennial grass recovery"(Allington and Valone). That is to say that although the result may not completely reliable they are the first to yield positive results which must be noted.

This report also demonstrates how each of these variables; soil compaction, water infiltration rates, soil quality, and erosion rates are all interrelated and therefore determine the growth of perennial grasses. Whether the effect is positive or negative depends on whether or not there is livestock grazing in the first place. In conclusion the data collected from this experiment although not 100% accurate proves that it is possible for desertified land to make a recovery. This information holds much promise landholders and governments who own regions of degraded land. Although the time frame it takes for the land to make an actual recovery is not realistic or reliable at the moment there are still numerous techniques and experiments that can be conducted in order to speed the process up.

By Sean Hergott

Reference:

Allington G., Valone T.J., "Reversal of desertification: The Role of physical and chemical soil properties." Journal of Arid Enviroments 74 (2010): 973-977. October 14 2010.