2.2.1 Causes of LU change
Use of a piece of land is obviously determined by its soil,
climate, topography & vegetation. Parallely, LUP of the region reflects importance
of the land with respect to its capability to support human activities, e.g. agriculture,
industry, forestry, energy production, settlement, recreation, and water availability.
Land is a fundamental factor of production, and through much of the course of
human history, it has been tightly coupled to economic growth (Richards 1990).
Thus LUP of an area is often a result of human interactions with the previous
(or original) LUP.
According to Schimel et al. (1991), Hobes et al. (1991) & Turner (1989), change
in LULC by human activities range from conversion of natural forest into cropland
and then to grassland. Such actives may be the result of very wide range of social
conditions e.g. need for food, fibre, living space, recreation etc. Population
density and the level of economic & social development generate the demands, which
are placed on the land, while the intensity of exploitation possibility depends
on the technology available.
Interpretations on how the different controlling factors interact to produce different
LULC in different contexts are controversial. There are many theories regarding,
which factors are the most important determinants. Further, controversy arises
in assessing the relative importance of different forces underlying LU decisions
in specific cases (Kumar, 1992).
It was suggested that the possible forces driving LUP change can be grouped into
six categories: population, level of affluence, technology, political economy,
political structure and attitudes & values (Stern et al. 1992). The first three
were linked to environmental change by the relationship
I=PAT
which indicates that environmental impact (I) is a function of population (P),
affluence (A) and technology (T) (Commoner, 1972). The relationships of these
three categories of driving forces with environmental change were statistically
analysed. Some of these works (Ambio, 1992; Meyer & Turner, 1992) specifically
addressed LULC change and suggested respective measures for each category of the
three categories of driving forces, i.e. P, A &T. Among these three P is the most
controversial one. Though on this variable world-wide data of reasonable accuracy
are available, when considered at global level as well as regional level opposite
views have been postulated by the different scientists on role of population growth
on environmental change. However comparative assessments of population and LU
change have revealed that population growth is positively correlated with the
expansion of agricultural land, LU intensification and deforestation, however
these relationships are weak.
Research on interaction of population, affluence and technology as causes of environmental
change or LUP change is not common. Although global comparisons indicate that
afforestation is largely a phenomenon of advanced industrial societies, which
are both affluent and have high technological capacity (Young et al. 1990), there
are mixed conclusions on the subject. It was opined (Brouwer and Chadwick, 1991)
that technological developments and their application may lead to major shifts
in LU in both developed and developing countries in coming decades.
The scientists working in the line added following three driving forces, to the
three forces discussed above, i.e. P, A & T:
* political economy including systems of exchange, ownership & control.
*political structure involving institutions and organisation of governance.
* attitudes and values of individuals and groups.
It was opined that these driving forces have received less attention than population
growth. These donot encompass clearly defined variables and causal relationships,
but comprise similar explanations of relationships of societal and environmental
change (Blaikie & Brookfield, 1987). Detailed examinations on the line could link
all these candidate forces. Some of the studies may be listed as follows:
*A model developed at Oak Ridge National Laboratory to assess socio-economic and
environmental interactives with LU reveals that improved transport facilities
are expected to exacerbate land degradation if the region in question is small,
but its impacts on larger regions will vary by circumstance (Jones and O'Neill,
1992).
*A study in Mexico indicates that local deforestation has caused a drop in local
water table (WT) and/or a reduction in local rainfall, and hence expanding the
area under cultivation to maintain production (Liverman, 1990).
Environmental transformations affect land-use, while assessments of the impacts
of climate on LULC rely on assumptions about LU change that can be improved through
studies of the dynamics of LU. However, there is a very weak stack of literature
on global aggregate on regional comparative studies on role of these proposed
six categories of driving forces. The major contributions on the studies conducted
on global scale can be listed as follows:-
* The major categories of the driving forces have been identified.
* Many driving forces are associated with environmental change over the long-term
and at a global level.
* Global-level aggregate relationships are difficult to demonstrate at sub-global
scales of analysis.
* Regional studies suggest the existence of generic relationships between the
causes of LU change and changes in LC.
* Integrated theories of the relationships between the human causes of LU change
and resulting change in LC are not suitably developed for testing or comparison.
At this stage it appears necessary to findout the links between human systems
generating changes in LUP and in physical systems that are affected by the resulting
changes in LCs. The driving forces interact and lead to actions reflecting demand
for LU which requires manipulation of LUP by means of technology like clearing,
ploughing, excavating, paving etc. Such interactions alter the morphology, cover,
quality (chemical & physical), composition & structure and hence usability of
the land. The consequences of these are change in climatic and other conditions
which in turn permit the users of land to act on the land. Morphology and quality
of land will identify its fitness for a specific use, e.g. fishery or swimming
pool, or industry or agriculture, or construction. Above all the economic, educational
and social characteristics of the user group will decide whether a piece of land
will be used for agriculture, or industry or an educational institute or a health
centre, or community development centre. Thus LUP of an area is a product of several
variables some dependent and some independent, all interacting with each other
forming a complex system. This perspective indicates that, understanding the global
environmental change needs understanding the conditions and changes in LC engineered
by changes in LU, the rates of alteration and modification of land characteirstics
and the human forces and societal conditions that influence the nature and rate
of activity of the processes. The concept has been detailed in Fig. 2.1.