Toxic Pollution 145
species, such as the predator-prey and the parasite-host relationships.
They often cause a large decline in the population of predators, followed
by a large increase in the prey species that constituted the target population of the biocide. The decline in predators may be caused either directly
by the poison or indirectly, due to the decline in the target population
and/or other organisms that serve as food for the predators. Furthermore,
synthetic biocides activate the mechanism of natural selection, with the
result that the hostile organisms develop resistance to their toxic action.
With their rapid reproduction, short life cycles and genetic diversification,
such organisms have an excellent ability to meet efforts at chemical control
head-on and render them ineffective. As the use of pesticides has increased,
there has been a rapid increase in the number of species that have developed resistance to one or more pesticides. In 1984 the number of resistant
parasites and insects had reached 448, whereas in 1954 it was only 24. The
creation of resistant varieties has inevitably led to increased applications
and dosage, mainly with more toxic pesticides, resulting in an intensification of the environmental problems.
7.3.2 non-toxic Means of Protecting
agricultural Production
It is necessary to control populations of insects and other hostile organisms,
particularly in agriculture. But even non-persistent biocides can lead to
environmental as well as economic impasses, without taking into account
the overall ecological consequences that may be entailed in their widespread,
intensive application.
One very interesting alternative is biological control through the introduction of natural enemies (predators or parasites). The implementation of
this method requires a careful study of the complex impacts the introduced
organisms may have on the environment—the introduction of a predatory
animal, the mongoose, to Jamaica to control rats ended in the extinction
of most of the small animals in the area. In any event, biological control
methods have been developed and improved substantially in recent years.
This was aided by the rapid growth of demand for so-called biological
products or organic or integrated farming produce. This is a market that
has already grown considerably, mainly in developed countries; it promotes
the production and consumption of plant and animal products using integrated or benign methods of agricultural production without the use of
toxic pesticides or other harmful substances.
There are other methods, more or less well developed, such as artificially increasing plants’ resistance to hostile organisms or using biological
substances that affect insects’ sexual behaviour, reproduction and growth.
The use of genetic engineering is another way to achieve protection of
agricultural production. Genetically modified plant varieties can resist
species, such as the predator-prey and the parasite-host relationships.
They often cause a large decline in the population of predators, followed
by a large increase in the prey species that constituted the target population of the biocide. The decline in predators may be caused either directly
by the poison or indirectly, due to the decline in the target population
and/or other organisms that serve as food for the predators. Furthermore,
synthetic biocides activate the mechanism of natural selection, with the
result that the hostile organisms develop resistance to their toxic action.
With their rapid reproduction, short life cycles and genetic diversification,
such organisms have an excellent ability to meet efforts at chemical control
head-on and render them ineffective. As the use of pesticides has increased,
there has been a rapid increase in the number of species that have developed resistance to one or more pesticides. In 1984 the number of resistant
parasites and insects had reached 448, whereas in 1954 it was only 24. The
creation of resistant varieties has inevitably led to increased applications
and dosage, mainly with more toxic pesticides, resulting in an intensification of the environmental problems.
7.3.2 non-toxic Means of Protecting
agricultural Production
It is necessary to control populations of insects and other hostile organisms,
particularly in agriculture. But even non-persistent biocides can lead to
environmental as well as economic impasses, without taking into account
the overall ecological consequences that may be entailed in their widespread,
intensive application.
One very interesting alternative is biological control through the introduction of natural enemies (predators or parasites). The implementation of
this method requires a careful study of the complex impacts the introduced
organisms may have on the environment—the introduction of a predatory
animal, the mongoose, to Jamaica to control rats ended in the extinction
of most of the small animals in the area. In any event, biological control
methods have been developed and improved substantially in recent years.
This was aided by the rapid growth of demand for so-called biological
products or organic or integrated farming produce. This is a market that
has already grown considerably, mainly in developed countries; it promotes
the production and consumption of plant and animal products using integrated or benign methods of agricultural production without the use of
toxic pesticides or other harmful substances.
There are other methods, more or less well developed, such as artificially increasing plants’ resistance to hostile organisms or using biological
substances that affect insects’ sexual behaviour, reproduction and growth.
The use of genetic engineering is another way to achieve protection of
agricultural production. Genetically modified plant varieties can resist