Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Jason Chmielewski
picture above shows satellite images taken of Lake Chad over a 40 year period,
representing the actual lake in blue. These images show that the lake has
experienced Desertification over the 40 year period. The lake has shrunk by 95%
since the 1960’s due to Desertification.
What is desertification?
Desertification is the process in which dry land ecosystems are deteriorated by
a combination of human growth and activity, and changes in the climate.
Desertification mainly occurs in semi-arid areas with an average annual rainfall
less than 600 millimeters. Poor land-management can also result in
desertification in areas that border a desert. Desertification affects the
wellbeing of people that rely on dry land ecosystems for support, which accounts
for about a third of the human population. The earth is made up of 71% water,
and 29% land, and of the 29% land, about half, or 14.5% is made up of dry lands.
Production of crops, wood, and other vegetation is limited due to the scarce
amount of water that is generally found in dry lands. The humans that live off
of these dry lands are slowly consuming all resources that they have to offer,
increasing climate variability. The Central Asian, and Saharan dry lands are
both becoming more and more vulnerable to the effects of desertification, mainly
due to these human pressures, and water scarcity. Desertification occurs on all
continents except Antarctica, and has already deteriorated 10 to 20 percent of
the Earth’s dry lands; making it one of the biggest environmental challenges in
the world today.
Major Causes of Desertification
The picture above shows the Rio Puerco Basin of central New
Mexico, one of the most eroded basins due to the overgrazing of livestock.
(Photo by Terrence Moore)
Desertification occurs as an area loses water and crucial soils as an outcome of water erosion. Water that comes through these dry lands, often times picks up some of the soils that are important for growing crops and other vegetation, and erodes them away. Irrigation is one of the major contributing factors of desertification as well, because it also takes all important minerals out of the soil, and can cause salinization, the buildup of salts in the soil, which can prevent the growth of vegetation. Much like the human skin after a dip in the pool, when water is added to the dry land, it will become even drier once the water evaporates. The humans that live off of these dry lands survive by hunting, gathering, farming, and herding. Herding the animals and allowing them to graze is also contributing to desertification. As human population grows, humans are putting more pressure on these areas, literally starving the dry lands of usable resources and water. Poor land-management can result in desertification in places that border deserts, such as Sahel. Sahel is a semi-arid area South of the Saharan Desert, that is slowly turning into desert itself. The Saharan desert moved 100km southward in a 25 year period between 1950, and 1975. Increasing human population, and drought will increase the rate of desertification dramatically over the years.
The Relationship Between Humans, and Desertification
The picture above shows the risk of human induced desertification
risks in Africa. The green means humans aren’t so much at risk of causing
desertification in the specific area, and red represents the areas that are at
risk of human induced desertification.
The availability of water and the climate conditions directly affect the
sustainability of a dry land ecosystem, and human presence. The well-being of
the dry land ecosystem depends on the growth of the plants being produced, which
directly depends on the amount of water available, and the climate conditions.
Humans rely on many dry land resources, such as crops, livestock, fuel wood, and
construction materials. These resources depend on the growth of the plants as
well, which in turn depends on water availability and climate. Therefore, the
sustainability of human life in a dry land ecosystem depends on water
availability and climate. When water resources deplete, and the climate begins
to change due to human pressures, the dry land ecosystem is no longer capable of
supporting life. Once an ecosystem has been starved of water, and can no longer
recover from previous pressures, desertification begins to follow.
Desertification leaves the land dead and useless, making it hard for the
inhabited humans to survive. The humans eventually migrate to a new dry land,
restarting the desertification process over, by pressuring the new area and
causing the new dry land to degrade.
Environmental Impacts of Desertification
The picture above shows a map of the world, using different
colors to represent areas that may be vulnerable to desertification. Is the area
you live in vulnerable?
Desertification is a worldwide phenomenon, already causing up to
10-20 percent of the world’s dry lands to degrade, and causing many more dry
lands to experience the effects of desertification. Not only does
desertification affect the direct area, but it also can have lasting
environmental impacts in other areas. An example of this is the loss of
vegetation. As vegetation is lost, the area is more open, and the ground becomes
a little loose As the plants reduce in cover area, soil is more exposed and
susceptible to accelerated erosion by wind and water. This leads to the
formation of large dust clouds, and frequent severe floods. These natural
disasters often time leave the dry land area, and begin destroying other areas
that are thousands of miles away, such as China. Dry lands of Asia and Africa
are the most affected by the environmental impacts of desertification, because
many of the counties affected by desertification are developing countries. This
makes it difficult for a country to develop, because as efforts are made to
develop the country, desertification is on its way to destroying it.
Can We Prevent or Reverse Desertification?
As the population
continues to grow, and the climate continues to change, desertification will
continue to occur, but how do we prevent it? There are two methods that can be
used to treat desertification. The first is prevention. Preventing
desertification from occurring in the first place is the most efficient way to
treat desertification, because it is the most cost effective method. The
Government and the people need to work together to change management strategies
both locally, and globally, to prevent and reverse desertification. Everybody on
Earth needs to come together to create some sort of program that promotes
conservation strategies to protect dry lands from desertification.
Desertification can be prevented by improving agriculture and animal grazing, in
order to allow the weak deserts time to become more sustainable. Rehabilitation
is also a method used to fight desertification, and could help restore degraded
ecosystems. A collaboration of policies, technologies, and community involvement
would be needed to reverse the effects of desertification. Human resources,
funds, and infrastructures would also play a crucial role in the rehabilitation
of the world’s degrading dry lands. Fencing infrastructures may be the cheapest,
and most efficient way of managing the land, because it would prevent animals
from moving in response to food availability, preventing overgrazing from taking
place. Small steps may be taken to reverse desertification, such as reducing the
number of animals in the area, allowing plants to regrow. Good land-management
is the only large scale approach to effectively preventing desertification.
The picture above depicts an example of what an area looks like
before (on the left) and after (on the right) the effects of desertification