Thursday August 1, 2013

Desertification refers to the expansion of deserts, or the conversion of non-desert land into desert. This process can take place naturally or can be greatly enhanced by human activity, such as excessive water usage.

When desertification is the result of natural causes, the process usually follows the steps of drought, land degradation, desertification. In researching desertification, almost all of the trends that I found were related to the human influence from excessive water use—which by the way has been constantly increasing for years mainly due to excessive irrigation and water consumption. In order to focus my search more on the climate change cause, I expanded my searches to drought trends.

According to the Environmental Protection Agency, the incidence of drought has remained fairly constant in the United States over the past 100 years. When one looks at the Palmer Drought Severity Index (PDSI), which is the most commonly method of assessing drought, there have been several dry periods in the last century but also considerable wet periods. Overall it is hard to establish a strong national trend that lasts more than a few decades. However, since the 1980’s the US has been on a general “drying” trend.

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http://www.epa.gov/climatechange/science/indicators/weather-climate/drought.html

When considering global trends, many of the sites that I referenced referred to a 2012 Princeton University and Australian National University study that suggested that the PDSI, which was developed for use in the American Midwest, actually overestimated the extent of global drought. The authors, who all seemed to be credible in their fields relating to Environmental Engineering and Water Resources, conducted a new analysis considering aspects such as wind speed, solar and infrared radiation, and humidity. The result showed less global drought than previously estimated, however, there is still a strong overall drying trend related to global drought… particularly across the Europe, African continent, and eastern Asia.

drought_trend_400.jpg

This study represented the extent of the disagreement regarding droughts and climate change that I could find. Opposed to it being a question of whether or not global drought would become more severe, the question was how severe it would become. According to a summary published (I couldn't find a full text of the actual study), the new analysis suggests that the extent of drought would increase at a rate of about one 7th the value projected by the Intergovernmental Panel on Climate Change in 2007. While I feel that the authors are well established in their field and are fairly reputable, I feel that between the number of initial web returns relating to the study and the seemingly doubtful tone that they cast on the future of global droughts, the discrepancy should be taken with a grain of salt.

http://www.nature.com/nature/journal/v491/n7424/full/nature11575.html
http://news.sciencemag.org/earth/2012/11/recent-drought-trends-not-so-cut-and-dried

A similar analysis by the US Department of agriculture presented in the form of a detailed map reveals that the areas most at risk of desertification are regions that currently border major deserts (much of Africa and the middle east), as well as areas that are accustomed to semi-permanent snow pack (the Rockies and Western US). I am inferring, the fact that the American west is at significant risk for desertification to be related to the loss of glaciers and snow pack resulting in a much drier local climate. This has the potential to lead to significant changes in local ecosystems as less water reserves in glaciers leads to drier soils, which in turn can completely affect the local vegetation throughout the local watershed. It can also affect how the local region responds to the normal rains/snow/heatwaves that it experiences.

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http://ossfoundation.us/projects/environment/global-warming/myths/images/changes-future/desertification_map_1920w.jpg/image_view_fullscreen

While there is some discrepancy over the extent of future droughts, it is generally accepted that the severity and length of droughts that do occur is getting worse. The main impacts that result from droughts are economic, agricultural, and social:

The impacts of increasing global drought in the coming years will have a huge impact on human life.
Firstly, droughts are extremely costly… in the past decades droughts and heatwaves have cost over $60 Billion dollars nationally. Additionally last year’s drought (which has actually continued into this summer) was the most extensive drought since the dust bowl, and cost $30 billion dollars alone.

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http://www.ncdc.noaa.gov/billions/events
http://droughtmonitor.unl.edu/

In Brazil, they are suffering from their worst drought on record. According to the international disasters database, this year’s drought has cost the country over $8 Billion, which makes it by far the country’s most costly natural disaster, surpassing the 1978 drought which was close to $2 Billion dollars. As of April 90% of the corn crop in Brazil’s 4th most populous state were lost, and prices of their flour staple were up by 700%. Half of the regions cattle had perished. Portions of the region have not seen rain in over a year, and may not see rain in the coming year.
http://www.wunderground.com/blog/JeffMasters/archive.html?year=2013&month=07
http://www.aljazeera.com/weather/2013/04/201341610554334393.html

Additionally, drought has played a role in social unrest throughout history. In recent years severe droughts across Asia and Russia in 2010 have been cited as having influenced the start of the Arab Spring movement by increasing political discontentment.
http://www.scientificamerican.com/article.cfm?id=climate-change-and-rising-food-prices-heightened-arab-spring

While the evidence seems to point to much stronger drought impacts in the coming years, not everyone will be affected.
One of the main impacts of climate change has been that it causes more extremes, resulting in more severe droughts but also more severe floods when it does rain. Examples of this can be seen in record rains/floods in Germany, Canada, and India this summer. For areas such as the Northeastern US, we are lucky in that we are relatively in the middle on the scale of extremes.

Because global trends are for regional droughts to become longer and more intense, it is vital that such risk regions be identified.
By identifying areas at risk for droughts, efforts can be made to educate local populations about water conservation techniques.
Techniques such as reusing sink and bath water are already being taught in response to Brazil's drought.
More affluent countries such as Australia have begun constructing seawater desalination plants.

After researching the intensity and affects of recent droughts, it is my opinion that despite increasing drought severity, most societies will be capable of enduring their periods of hardship. However, I expect that in many less affluent nations -mainly across Africa and portions of South America- droughts this century will play a large role in shaping their future economies and patterns of settlement. Currently, based on the intensity and length of the Brazil drought, I would not be surprised to see a greater number of rural villagers migrating to the cities where 1) they could potentially find more profitable work than farming in a drought, 2) there may be a greater amount of resources such as water and food. The most widely felt effect will be increased grain prices as agricultural regions are effected. This is what I project to be the future influence of climate change as it relates to drought and desertification.

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