28.4 Human Activity and the Environment: Land-use Systems
421
quality of aquatic ecosystems. Economic and demographic processes are intimately linked. Industrialization and trade are tied to urbanization. Urbanization includes redistribution of population,
migration from rural areas, and the commercialization of rural agricultural systems. Industrialization and urbanization are often associated with improved health care and education, sanitation, and
water supply. These stimulate reductions in death
rates and contribute to demographic transition in
the form of urban and rural population growth.
Different types of industrial activity have distinctive impacts on ecosystems. Mining may have
only a localized impact, whereas processing of minerals can contribute to urbanization with its attendant demands on ecosystems and, through waste
production, can affect atmospheric and hydrological systems. Urban development entails conversion
ofland use to urban forms. Rural popUlation growth
is associated with extensification of agriculture, involving replacement of forest or other land cover
by crop or animal production, or with intensification of land use.
Care is required in the assessment of the ecological impact of such land cover or use changes.
The impact is most intense at the time of initial
transformation from one use or cover to another,
for example, from forest to agriculture, agriculture
to suburbia, riparian forest to irrigated crop production, or lakeshore to recreational activities. As
the new land uses mature, they may, over time, replace some ecosystem functions that were lost in
the initial transformation. Others may be permanently damaged or lost.
There is a temptation to assume that the losses
incurred at the time of initial transformation are
permanent and irreparable. This is not necessarily
the case. Whether impacts are irreparable depends
on criteria for evaluation. For example, where an
area of forest is replaced by cultivation, there may
be initial disruptions or destruction of habitat, loss
of biodiversity, diminished carbon cycling, and disturbance of drainage. Cultivators seldom seek to
destroy the resource base; rather, actions are taken
to enhance their livelihoods. For example, they may
plant trees to maintain productivity, to achieve esthetic objectives, and to establish land rights. These
trees may also restore drainage regimes and revive
carbon cycling, and, while they may create a different biodiversity, they may not re-establish the
same habitats. There may be gains, losses, or equivalence in outcomes depending on the objective criteria. Where the outcomes pit societal objectives,
such as promotion of livelihoods, against ecological ones, then the objective criteria are complex,
and the power of interest groups usually determines
the political outcome.
Categories of Economic Activity
Land use can be classified into four categories of
economic activity: primary, secondary, tertiary and
quaternary. Each of these has different demands of
and impacts on ecosystems. These may change in
nature from the time they are initiated to those related to their long-term functioning.
Primary activities are those that derive their economic utility directly from aquatic or terrestrial resources. These include agriculture, fishing, mining,
forestry, and wilderness or wildlife-based tourism.
Some of these, such as agriculture, forestry, and often wilderness and wildlife, are extensive land uses.
They therefore have a greater impact on overall
land cover than other activities.
The density of population that primary activities
support depends on a variety of factors. In industrial societies such as those of North America and
Europe, rural population densities are low and the
pattern of associated urban development is one of
relatively small towns that act as markets and service centers. The processing of products often takes
place far from the point of production. In other parts
of the world, rural population densities are similar
to those of suburban areas in the United States. In
Rwanda, for example, densities of over 800 people
per square kilometer were reported by the 1991
census.
The distribution of population associated with
other primary activities, such as fishing and mining, is more localized. Although fishing makes extensive use of aquatic ecosystems, the fleets are
based in ports, giving the industry a localized terrestrial pattern. The distribution and exploitation of
mineral resources is also localized. Furthermore,
the characteristics of the primary product, the perishability of fish and the impurity of most ores, attract industries that use these products as raw materials to the point of production, such as the ports
and mines.
The processing of primary products creates secondary economic activity. Forestry is the basis for
furniture making; mining of iron, coal, and limestone is the foundation of the steel industry; and
agriculture supports the food-processing industry.
These secondary activities have locational requirements that are internal to the production unit and
others that relate to other associated industrial activities. The weighing of the relative importance of
these determines the location of production.
Costs ofland, labor, capital, and transport are the
421
quality of aquatic ecosystems. Economic and demographic processes are intimately linked. Industrialization and trade are tied to urbanization. Urbanization includes redistribution of population,
migration from rural areas, and the commercialization of rural agricultural systems. Industrialization and urbanization are often associated with improved health care and education, sanitation, and
water supply. These stimulate reductions in death
rates and contribute to demographic transition in
the form of urban and rural population growth.
Different types of industrial activity have distinctive impacts on ecosystems. Mining may have
only a localized impact, whereas processing of minerals can contribute to urbanization with its attendant demands on ecosystems and, through waste
production, can affect atmospheric and hydrological systems. Urban development entails conversion
ofland use to urban forms. Rural popUlation growth
is associated with extensification of agriculture, involving replacement of forest or other land cover
by crop or animal production, or with intensification of land use.
Care is required in the assessment of the ecological impact of such land cover or use changes.
The impact is most intense at the time of initial
transformation from one use or cover to another,
for example, from forest to agriculture, agriculture
to suburbia, riparian forest to irrigated crop production, or lakeshore to recreational activities. As
the new land uses mature, they may, over time, replace some ecosystem functions that were lost in
the initial transformation. Others may be permanently damaged or lost.
There is a temptation to assume that the losses
incurred at the time of initial transformation are
permanent and irreparable. This is not necessarily
the case. Whether impacts are irreparable depends
on criteria for evaluation. For example, where an
area of forest is replaced by cultivation, there may
be initial disruptions or destruction of habitat, loss
of biodiversity, diminished carbon cycling, and disturbance of drainage. Cultivators seldom seek to
destroy the resource base; rather, actions are taken
to enhance their livelihoods. For example, they may
plant trees to maintain productivity, to achieve esthetic objectives, and to establish land rights. These
trees may also restore drainage regimes and revive
carbon cycling, and, while they may create a different biodiversity, they may not re-establish the
same habitats. There may be gains, losses, or equivalence in outcomes depending on the objective criteria. Where the outcomes pit societal objectives,
such as promotion of livelihoods, against ecological ones, then the objective criteria are complex,
and the power of interest groups usually determines
the political outcome.
Categories of Economic Activity
Land use can be classified into four categories of
economic activity: primary, secondary, tertiary and
quaternary. Each of these has different demands of
and impacts on ecosystems. These may change in
nature from the time they are initiated to those related to their long-term functioning.
Primary activities are those that derive their economic utility directly from aquatic or terrestrial resources. These include agriculture, fishing, mining,
forestry, and wilderness or wildlife-based tourism.
Some of these, such as agriculture, forestry, and often wilderness and wildlife, are extensive land uses.
They therefore have a greater impact on overall
land cover than other activities.
The density of population that primary activities
support depends on a variety of factors. In industrial societies such as those of North America and
Europe, rural population densities are low and the
pattern of associated urban development is one of
relatively small towns that act as markets and service centers. The processing of products often takes
place far from the point of production. In other parts
of the world, rural population densities are similar
to those of suburban areas in the United States. In
Rwanda, for example, densities of over 800 people
per square kilometer were reported by the 1991
census.
The distribution of population associated with
other primary activities, such as fishing and mining, is more localized. Although fishing makes extensive use of aquatic ecosystems, the fleets are
based in ports, giving the industry a localized terrestrial pattern. The distribution and exploitation of
mineral resources is also localized. Furthermore,
the characteristics of the primary product, the perishability of fish and the impurity of most ores, attract industries that use these products as raw materials to the point of production, such as the ports
and mines.
The processing of primary products creates secondary economic activity. Forestry is the basis for
furniture making; mining of iron, coal, and limestone is the foundation of the steel industry; and
agriculture supports the food-processing industry.
These secondary activities have locational requirements that are internal to the production unit and
others that relate to other associated industrial activities. The weighing of the relative importance of
these determines the location of production.
Costs ofland, labor, capital, and transport are the