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D.T. Sol brig
formity. Traditional varieties were genetically diverse. As these are replaced by
high yielding ones, genetic diversity is reduced dramatically, threatening the genetic base on which plant breeders depend to obtain newer and better varieties in
the future. An effort to preserve genetic diversity is the establishment of a network
of gene banks (National Academy of Science 1993). Yet, these gene banks only
preserve a small part of the gene diversity. This is one of the most serious problems
associated with the loss of biodiversity.
5 Native Ecosystems
For the most part people have given little thought to the conservation of that part of
the Earth's surface not directly involved in the productive process, what has been
called rustic landscapes (Halffter 1999). Natural ecosystems are as important as
human-made ones in sustaining life, through their role in such processes as water
and nutrient cycling, storing carbon, fixing atmospheric nitrogen and liberating
oxygen. However, most of these landscapes have also been profoundly affected by
human activities.
This problem has many facets. In the developed world it takes the form of urban
sprawl, especially in the United States. In a belt surrounding large cities, housing
developments and factories advance on natural landscapes and highly productive
agricultural land destroying or profoundly affecting the function of the ecosystem.
In other areas it takes the form of deforestation, or destruction of woody species in
quest for firewood, or degradation of ecosystem by uncontrolled grazing. Whatever
its form, the result is always the same: reduced primary productivity, reduced capacity of nutrient and water cycling, and loss of potential habitat for many species.
One of our innate beliefs derived from thousands, if not millions of years of
human evolution, is that nature takes care of itself. When we pick an apple from a
tree we never think of the consequences to the tree or the ecosystem. In the past,
hunter-gatherer bands foraged in a given territory as long as the energy obtained
from the food compensated for the effort involved in obtaining it. Once an area
does not produce sufficient food to compensate for the energy needed to gather it, a
hunter-gatherer band moves to another site. Natural ecosystems present us with the
fruits, the seeds, the roots, and the game. "Nature" takes care of the upkeep of the
system and the cost of production.
In a natural ecosystem, the impact of each species in the food chain, although
not negligible, is part of the characteristics of the ecosystem, and the evolution of
each species popUlation is in part a response to the changes wrought by other species. As any given species increases its numbers at the cost of another it becomes a
powerful selective force in the life of the secondary species. Sometimes that struggle
leads to the disappearance of a prey species, which in turn affects the survival of the
predator, but often an arms race ensues where each species increases its defenses,
its competitive abilities, or its ability to penetrate the defenses of another one, as the
case may be, resulting in a dynamic equilibrium.
D.T. Sol brig
formity. Traditional varieties were genetically diverse. As these are replaced by
high yielding ones, genetic diversity is reduced dramatically, threatening the genetic base on which plant breeders depend to obtain newer and better varieties in
the future. An effort to preserve genetic diversity is the establishment of a network
of gene banks (National Academy of Science 1993). Yet, these gene banks only
preserve a small part of the gene diversity. This is one of the most serious problems
associated with the loss of biodiversity.
5 Native Ecosystems
For the most part people have given little thought to the conservation of that part of
the Earth's surface not directly involved in the productive process, what has been
called rustic landscapes (Halffter 1999). Natural ecosystems are as important as
human-made ones in sustaining life, through their role in such processes as water
and nutrient cycling, storing carbon, fixing atmospheric nitrogen and liberating
oxygen. However, most of these landscapes have also been profoundly affected by
human activities.
This problem has many facets. In the developed world it takes the form of urban
sprawl, especially in the United States. In a belt surrounding large cities, housing
developments and factories advance on natural landscapes and highly productive
agricultural land destroying or profoundly affecting the function of the ecosystem.
In other areas it takes the form of deforestation, or destruction of woody species in
quest for firewood, or degradation of ecosystem by uncontrolled grazing. Whatever
its form, the result is always the same: reduced primary productivity, reduced capacity of nutrient and water cycling, and loss of potential habitat for many species.
One of our innate beliefs derived from thousands, if not millions of years of
human evolution, is that nature takes care of itself. When we pick an apple from a
tree we never think of the consequences to the tree or the ecosystem. In the past,
hunter-gatherer bands foraged in a given territory as long as the energy obtained
from the food compensated for the effort involved in obtaining it. Once an area
does not produce sufficient food to compensate for the energy needed to gather it, a
hunter-gatherer band moves to another site. Natural ecosystems present us with the
fruits, the seeds, the roots, and the game. "Nature" takes care of the upkeep of the
system and the cost of production.
In a natural ecosystem, the impact of each species in the food chain, although
not negligible, is part of the characteristics of the ecosystem, and the evolution of
each species popUlation is in part a response to the changes wrought by other species. As any given species increases its numbers at the cost of another it becomes a
powerful selective force in the life of the secondary species. Sometimes that struggle
leads to the disappearance of a prey species, which in turn affects the survival of the
predator, but often an arms race ensues where each species increases its defenses,
its competitive abilities, or its ability to penetrate the defenses of another one, as the
case may be, resulting in a dynamic equilibrium.