Image Processing Reference
In-Depth Information
13.1.1
Status and Extent of Desertification
Desertification is defined by the United Nations Convention to Combat Desertification
(UNCCD) as a decline in land productivity in arid, semi-arid
and dry sub-humid regions, resulting from many factors,
such as human activities and climate changes (UNCCD
1994
). It is a world-wide phenomenon that has a profound
effect, especially in Africa and West-Asia. According to a
global assessment undertaken by the United Nations
Environment Program (UNEP) in
1991
, around 70% of the
arid and semi-arid areas (excluding hyper-arid deserts) are
affected by desertification. The economic losses of such
phenomenon are estimated at US$42.3 billion per year.
These consequences have affected more than 100 countries,
80 of which are developing countries that account for
approximately one sixth of the world population. The main
causes beyond increased desertification are: deforestation,
overgrazing, fuel wood consumption, agricultural misman-
agement, wind and water erosion, urbanization, and industry.
The severe climatic conditions and the demographic
explosion have pushed the rural population in poverty, and
forced them to immigrate to the near cities and live in diffi-
cult socioeconomic conditions. These immigrants put a huge strain on services (e.g.,
housing, water, waste, health) and infrastructure (e.g., transport, education) resources that
are already overstretched. As the demand of housing increases, cities begin to expand
into new areas (Chapter 2). This in turn causes urban development to expand into natural
areas such as deserts, rangelands, and agricultural lands. Figure
13.1
shows a flowchart
designed for desertification monitoring and control using both conventional and remotely
sensed data (Ait Belaid 1999).
desertification is a
world-wide
phenomenon
defined as a
decline in land
productivity in
arid, semi-arid and
dry sub-humid
regions due to such
factors as human
activities,
population growth,
climate changes,
agricultural
mismanagement,
and fuel wood
consumption
13.1.2
Urban Areas in Africa
The majority (62.1%) of African population is still rural,
but the urban population is expected to increase from
10% to 17% between 2000 and 2013. North Africa is the
most urbanized sub-region, with an average urban popu-
lation of about 54% of the total populations in countries
located in this region. The least urbanized African sub-
region is Eastern Africa with only 23% of the popula-
tion living in urban areas (UNPD 2001).
The number of African cities is increasing and exist-
ing cities are expanding in coverage. About 43 African
cities have population greater than one million inhabitants
Africa's high
urban growth rate
is a result of
rural-urban
immigration,
population growth,
and in some areas,
conflict and
environmental
disasters
