The Measurements of Desertification
“Drought and desertification threaten the livelihood of over one
billion people in more than 110 countries” warned general Kofi in 2001
(Kovach,2003). Desertifications definition is highly disputed but it
is generally the shift of arid or semi-arid regions to desert-like
conditions, which support: little vegetation, a low soil fertility and
high evaporation rates (Haggett, 2001). This work will overlook how
deserts are measured by a variety of different means.
To measure the growth of deserts characteristics need to be obtained.
By creating set indicators for deserts the spread of desertification
can be gauged. Climate (Anderson,2001) is one of the larger indicators
of the spread of deserts: as you can see from appendix 1B, the worlds
deserts are in general located in and around the equatorial region and
the tropics. Due to this they are influenced heavily by the movements
of the inter-continental convergence zone (ITCZ) which generates
areas of high pressure over deserts such as the Sahara desert and due
to this there is little precipitation for the whole year (below 25mm)
(Berrahmouni, 2001). Desert zones receive little rain during a year
but when they do it is heavy and sporadic and causes much soil erosion
(Sharma,1997). So by gauging precipitation levels around arid and
semi-arid regions meteorologists can approximate as to how ‘at risk’
the area is. As without a decent supply of precipitation, soil
infrastructure and fertility will decline due to a lack of moisture
and the denaturing of the surrounding biota i.e. roots and nutrient
cycles (Sharma,1997). National monthly rainfall index (NMRI) (UN) is
used to measure monthly changes in precipiatation, weighjted against
the yearly averages (UN, 2004).
Also the local flora and fauna act as indicators of desertification:
vegetation cover allows biologists to define weather the areas flora
is decreasing in number (UN,2004) and thus potentially allowing for
land degradation to set in (the forerunner to desertification). Also
the types of vegetation in potential risk areas is important: the
appearance of xerophytes indicates that there is little groundwater,
also the appearance of halophytes would indicate higher than average
soil salinity and perhaps the onset of soil salinisation (Saouma,
1993) – which again shadows desertification and land degradation.
Also the presence of humans and the land-uses that...