Ecology: historical background

Ecology had no firm beginnings. It evolved from the natural history of the Greeks, particularly Theophrastus, a friend and associate of Aristotle. He first described the interrelationships between organisms and between organisms and their nonliving environment. Later foundations for modern ecology were laid in the early work of plant and animal physiologists.

In the early and mid-1900s two groups of botanists, one in Europe and the other in America, studied plant communities from two different points of view. The European botanists concerned themselves with the study of the composition, structure, and distribution of plant communities. The American botanists studied the development of plant communities, or succession. Both plant and animal ecology developed separately until American biologists emphasized the interrelation of both plant and animal communities as a biotic whole.

During the same period interest in population dynamics developed. The study of population dynamics received special impetus in the early 19th century, after Thomas Malthus called attention to the conflict between expanding populations and the capability of the earth to supply food. R. Pearl (1920), A.J. Lotka (1925), and V. Volterra (1926) developed mathematical foundations for the study of populations, and these studies led to experiments on the interaction of predators and prey, competitive relationships between species, and the regulation of populations. Investigations of the influence of behaviour on populations was stimulated by the recognition in 1920 of territoriality in nesting birds. Concepts of instinctive and aggressive behaviour were developed by K. Lorenz and N. Tinbergen, and the role of social behaviour in the regulation of populations was explored by V.C. Wynne-Edwards.

While some ecologists were studying the dynamics of communities and populations, others were concerned with energy-budgets. In 1920, August Thienemann, a German freshwater biologist, introduced the concept of trophic, or feeding, levels, by which the energy of food is transferred through a series of organisms, from green plants (the producers) up to several levels of animals (the consumers). An English animal ecologist, C.E. Elton (1927), further developed this approach with the concept of ecological niches and pyramids of numbers. Two American freshwater biologists, E. Birge and C. Juday, in the 1930s, in measuring the energy budgets of lakes, developed the idea of primary production, i.e., the rate at which food energy is generated, or fixed, by photosynthesis. Modern ecology came of age in 1942 with the development, by R.L. Lindeman of the United States, of the trophic-dynamic concept of ecology, which details the flow of energy through the ecosystem. Quantified field studies of energy flow through ecosystems were further developed by Eugene and Howard Odum of the United States; similar early work on the cycling of nutrients was done by J.D. Ovington of England and Australia.

The study of both energy flow and nutrient cycling was stimulated by the development of new techniques—radioisotopes, microcalorimetry, computer science, and applied mathematics—that enabled ecologists to label, trace, and measure the movement of particular nutrients and energy through the ecosystems. These modern methods encouraged a new stage in the development of ecology—systems ecology, which is concerned with the structure and function of ecosystems.

Until the late 20th century ecology lacked a strong conceptual base. Modern ecology, however, is now focussed on the concept of the ecosystem, a functional unit consisting of interacting organisms and all aspects of the environment in any specific area. It contains both the nonliving (abiotic) and living (biotic) components through which nutrients are cycled and energy flows. To accomplish this cycling and flow, ecosystems must possess a number of structured interrelationships between soil, water, and nutrients, on the one hand, and producers, consumers, and decomposers on the other. Ecosystems function by maintaining a flow of energy and a cycling of materials through a series of steps of eating and being eaten, of utilization and conversion, called the food chain. Ecosystems tend toward maturity, or stability, and in doing so they pass from a less complex to a more complex state. This directional change is called succession. Whenever an ecosystem is used, and that exploitation is maintained—as when a pond is kept clear of encroaching plants or a woodland is grazed by domestic cattle—the maturity of the ecosystem is effectively postponed. The major functional unit of the ecosystem is the population. It occupies a certain functional niche, related to its role in energy flow and nutrient cycling. Both the environment and the amount of energy fixation in any given ecosystem are limited. When a population reaches the limits imposed by the ecosystem, its numbers must stabilize or, failing this, decline from disease, starvation, strife, low reproduction, or other behavioral and physiological reactions. Changes and fluctuations in the environment represent selective pressure upon the population to which it must adjust. The ecosystem has historical aspects: the present is related to the past and the future to the present. Thus the ecosystem is the one concept that unifies plant and animal ecology, population dynamics, behaviour, and evolution.

 

TEXT 2

ENVIRONMENTAL POLLUTION

Environmental pollution is the addition of any substance or form of energy (e.g., heat, sound, radioactivity) to the environment at a rate faster than the environment can accommodate it by dispersion, breakdown, recycling, or storage in some harmless form.

A pollutant need not be harmful in itself. Carbon dioxide, for example, is a normal component of the atmosphere and a by-product of respiration that is found in all animal tissues; yet in a concentrated form it can kill animals. Human sewage can be a useful fertilizer, but when concentrated too highly it becomes a serious pollutant, menacing health and causing the depletion of oxygen in bodies of water. By contrast, radioactivity in any quantity is harmful to life, despite the fact that it occurs normally in the environment as so-called background radiation.

Pollution has accompanied mankind ever since groups of people first congregated and remained for a long time in any one place. Primitive human settlements can be recognized by their pollutants—shell mounds and rubble heaps. But pollution was not a serious problem as long as there was enough space available for each individual or group. With the establishment of permanent human settlements by great numbers of people, however, pollution became a problem and has remained one ever since. Cities of ancient times were often noxious places, fouled by human wastes and debris. In the Middle Ages, unsanitary urban conditions favoured the outbreak of population-decimating epidemics. During the 19th century, water and air pollution and the accumulation of solid wastes were largely the problems of only a few large cities. But, with the rise of advanced technology and with the rapid spread of industrialization and the concomitant increase in human populations to unprecedented levels, pollution has become a universal problem.

The various kinds of pollution are most conveniently considered under three headings: air, water, and land.

 

TEXT 3

WATER POLLUTION

Water pollution involves the release into lakes, streams, rivers, and oceans of substances that become dissolved or suspended in the water or deposited upon the bottom and accumulate to the extent that they interfere with the functioning of aquatic ecosystems. It may also include the release of energy in the form of radioactivity or heat, as in the case of thermal pollution. Any body of water has the capacity to absorb, break down, or recycle introduced materials. Under normal circumstances, inorganic substances are widely dispersed and have little or no effect on life within the bodies of water into which they are released; organic materials are broken down by bacteria or other organisms and converted into a form in which they are useful to aquatic life. But, if the capacity of a body of water to dissolve, disperse, or recycle is exceeded, all additional substances or forms of energy become pollutants. Thus, thermal pollution, which is usually caused by the discharge of water that has been used as a coolant in fossil-fueled or nuclear-power plants, can favour a diversity of aquatic life in waters that would otherwise be too cold. In a warmer body of water, however, the addition of heat changes its characteristics and may make it less suited to species that are considered desirable.

Pollution may begin as water moves through the air, if the air is polluted. Soil erosion adds silt as a pollutant. The use of chemical fertilizers, pesticides, or other materials on watershed lands is an additional factor contributing to water pollution. The runoff from septic tanks and the outflow of manures from livestock feedlots along the watershed are sources of organic pollutants. Industries located along waterways downstream contribute a number of chemical pollutants, some of which are toxic if present in any concentration. Finally, cities and towns contribute their loads of sewage and other urban wastes. Thus, a community far upstream in a watershed may receive relatively clean water, whereas one farther downstream receives a partly diluted mixture of urban, industrial, and rural wastes. The cost of cleaning and purifying this water for community use may be high, and the process may be only partially effective. To add to the problem, the cities and towns in the lower, or downstream, regions of the river basin contribute additional wastes that flow into estuaries, creating new pollution problems.

The output of industries, agriculture, and urban communities generally exceeds the biologic capacities of aquatic systems, causing waters to become choked with an excess of organic substances and organisms to be poisoned by toxic materials. When organic matter exceeds the capacity of those microorganisms in water that break it down and recycle it, the excess of nutrients in such matter encourages rapid growth, or blooms, of algae. When they die, the remains of the dead algae add further to the organic wastes already in the water; eventually, the water becomes deficient in oxygen. Anaerobic organisms (those that do not require oxygen to live) then attack the organic wastes, releasing gases such as methane and hydrogen sulfide, which are harmful to the oxygen-requiring (aerobic) forms of life. The result is a foul-smelling, waste-filled body of water, a situation that has already occurred in such places as Lake Erie and the Baltic Sea and is a growing problem in freshwater lakes of Europe and North America. The process by which a lake or any other body of water changes from a clean, clear condition—with a relatively low concentration of dissolved nutrients and a balanced aquatic community—to a nutrient-rich, algae-filled body and thence to an oxygen-deficient, waste-filled condition is known as accelerated eutrophication.

Water quality Natural water quality is a dilute solution of elements dissolved from the Earth's crust or washed from the atmosphere. Its ionic concentration varies from less than 100 milligrams per litre in snow, rain, hail, and some mountain lakes and streams to as high as 400,000 milligrams per litre in the saline lakes of internal drainage systems or old groundwaters associated with marine sediments.

Water quality is influenced by natural factors and by human activities, both of which are the subject of much hydrologic study. The natural quality of water varies from place to place with climate and geology, with stream discharge, and with the season of the year. After precipitation reaches the ground, water percolates through organic material such as roots and leaf litter, dissolves minerals from the soil and rock through which it flows, and reacts with living things from microscopic organisms to humans. Water quality also is modified by temperature, soil bacteria, evaporation, and other environmental factors.

Pollution is the degradation of water quality by human activities. Pollution of surface and subsurface waters arises from many causes, but it is having increasingly serious effects on hydrologic systems. In some areas the precipitation inputs to the system are already highly polluted, primarily by acids resulting from the combustion of fossil fuels in power generation and automobiles.

Other serious causes of pollution have been the dumping of industrial wastes and the discharge of untreated sewage into watercourses. Salt spread on roads in winter has resulted in the contamination of subsurface drinking water supplies in certain areas, as, for example, in Long Island, New York. Excess water resulting from deforestation or irrigation return flows that leach salts from soils in semiarid areas are major sources of pollution in the western United States and Western Australia.

 

 

TEXT 4

LAND POLLUTION

Land pollution involves the deposition on land of solid wastes—e.g., used cars, cans, bottles, plastic containers, paper—that cannot be broken down quickly or, in some instances, cannot be broken down at all by the action of organic or inorganic forces. (The term biodegradable is used to describe those materials that can be decomposed and recycled by biological action.) When such materials become concentrated within any one area, they interfere with organic life and create unsightly accumulations of trash. Methods of disposal other than recycling include ocean dumping, which creates water pollution and destroys marine habitats; landfill, which often requires the availability of low-lying ground and frequently involves the destruction of marshland or swamps that have high biological value; and burning, which increases air pollution. Obviously, none of these methods is entirely satisfactory, although using landfill to create artificial landscapes, which then are covered with soil and planted with various kinds of vegetation, is a possibility that remains to be fully developed. It is the great quantity of debris produced by urban communities, more so than a shortage of raw materials, that forces the development of more effective means for recycling wastes. Land pollution also involves the accumulation on land of substances in dispersed solid or liquid form that are injurious to life. This has been particularly noticeable with those chemicals (e.g., DDT) that are spread for the purpose of exterminating pests but then accumulate to the extent that they can do damage to many other forms of life.

 

Chemical pollutants Among the most serious chemical pollutants are the chlorinated hydrocarbon pesticides, such as DDT, aldrin, and dieldrin; the polychlorinated biphenyls (PCBs), which are used in a variety of industrial processes and in the manufacture of many kinds of materials; and such metals as mercury, lead, cadmium, arsenic, and beryllium. All of these substances persist in the environment, being slowly, if at all, degraded by natural processes; in addition, all are toxic to life if they accumulate in any appreciable quantity.

The persistent pesticides have created serious ecological problems. As they move through successively higher organisms in food chains, they accumulate in increasingly concentrated forms at each level, causing damaging effects to the predators at the end of the chains—i.e., they are present in low quantities in simple organisms but become more concentrated as these organisms are consumed by more complex ones, which are themselves consumed by predators. Among the species known to be adversely affected are such meat-eating birds as falcons, hawks, and eagles and such fish-eating birds as pelicans, petrels, cormorants, and egrets. The reproduction capacity of all of these birds has been affected by an accumulation of DDT or a similar compound in their tissues. This is manifested by an impairment in the ability of the females to form eggshells properly. As a result, some species lay soft-shelled or shell-less eggs that cannot be hatched, and there has been a general decline in the numbers of these birds in Europe, Japan, and North America. Although the effects of the same chemicals on mammals is less obvious and still a matter for investigation, some studies suggest that DDT can reduce the productivity of plant plankton, upon which all other marine life depends.

There also is substantial evidence that pesticides lose the ability to control the pests they were designed to kill. Many insect species have developed immunity to a wide range of synthetic pesticides, and the resistance is inherited by their offspring. Furthermore, it has been observed that repeated use of such chemicals creates pest populations in areas in which none previously existed. This happens because the pesticides destroy populations of carnivorous, predatory insects that had in the past kept the plant-eating insects in check.

Among other materials that are harmful to most forms of life are such metals as mercury, lead, and arsenic. The increasing release of these substances into the biosphere by industrial processes has created conditions that are now generally viewed as harmful to human welfare. Studies have been conducted on metallic pollutants to determine the normal environmental levels, the levels that are toxic to humans, and the extent to which industrial processes are responsible for the problem.

The ultimate control of pollution will presumably involve the decision not to allow the escape into the environment of the substances that are harmful to life, the decision to contain and recycle those substances that could be harmful if released into the environment in excessive quantities, and the decision not to release into the environment substances that persist and are toxic to living things. Essentially, therefore, pollution control does not mean an abandonment of existing productive human activities but their reordering so as to guarantee that their side effects do not outweigh their advantages.

 

TEXT 5

GREENPEACE

Greenpeace is an international organization dedicated to preserving endangered species of animals, preventing environmental abuses, and heightening environmental awareness through direct confrontations with polluting corporations and governmental authorities. Greenpeace was founded in 1971 in British Columbia to oppose U.S. nuclear testing at Amchitka Island in Alaska. The loose-knit organization quickly attracted support from ecologically minded individuals and began undertaking campaigns seeking, among other goals, the protection of endangered whales and seals from hunting, the cessation of the dumping of toxic chemical and radioactive wastes at sea, and the end of nuclear-weapons testing. The primary tactic of Greenpeace has been such “direct, nonviolent actions” as steering small inflatable craft between the harpoon guns of whalers and their cetacean prey and the plugging of industrial pipes discharging toxic wastes into the oceans and the atmosphere. Such dangerous and dramatic actions brought Greenpeace wide media exposure and helped mobilize public opinion against environmentally destructive practices. Greenpeace also actively sought favourable rulings from national and international regulatory bodies on the control of environmental abuses, sometimes with considerable success. The organization has a small staff and relies largely on voluntary staffing and funding.

On July 10, 1985, the Greenpeace ship Rainbow Warrior, which was due to sail to Moruroa Atoll to protest French atmospheric nuclear-weapons tests there, was sunk by two bomb explosions while berthed in Auckland Harbour, N.Z. Subsequent revelations that French intelligence agents had planted the bombs caused a major international scandal and led to the resignation of France's minister of defense and the dismissal of the head of its intelligence service.

The Greens, also called Green Party, any of various environmentalist or ecological-oriented political parties formed in European countries and various countries elsewhere beginning in 1979. An umbrella organization known as the European Greens was founded in Brussels, Belg., in January 1984 to coordinate the activities of the various European parties, and Green representatives in the European Parliament sit in the Rainbow Group.

The first and most successful party known as the Greens (die Grunen) was founded in West Germany by Herbert Gruhl, Petra Kelly, and others in 1979 and arose out of the merger of about 250 ecological and environmentalist groups. The party sought to organize public support for the control of nuclear energy and of air and water pollution. The Greens became a national party in 1980. The program that they adopted called for the dismantling of both the Warsaw Pact and NATO, the demilitarization of Europe, and the breaking up of large economic enterprises into smaller units, among other proposals. This program attracted many members of the left wing of the Social Democratic Party into the Greens' ranks. The Greens won a sprinkling of seats in various Land (state) elections from 1979 on, and in 1983 they won a 5.6 percent share of the vote in national elections to the Bundestag (Federal Diet), thereby achieving their first representation in that legislative chamber. The Greens experienced almost constant ideological tensions between its left wing and a more pragmatic faction. Its members were largely well-educated young people, but the party drew considerable support from voters concerned about local or regional environmental and other issues.

By the end of the 1980s almost every country in western and northern Europe had a party known as the Greens or by some similar name (e.g., Green List in Italy, Green Alliance in Ireland and Finland, Green Alternatives in Austria, Green Ecology Party in Sweden, Ecologist Party in Belgium). Green parties developed also overseas in such countries as Canada, Australia, New Zealand, Argentina, and Chile. After the revolutions of 1989, Green parties or groups also began to emerge in eastern Europe.

 

TEXT 6

SOIL

Soil is the biologically active, porous medium that has developed in the uppermost layer of the Earth's crust. Soil is one of the principal substrata of life on Earth, serving as a reservoir of water and nutrients, as a medium for the filtration and breakdown of injurious wastes, and as a participant in the cycling of carbon and other elements through the global ecosystem. It has evolved through weathering processes driven by biological, climatic, geologic, and topographic influences.

Soils differ widely in their properties because of geologic and climatic variation over distance and time. Even a simple property, such as the soil thickness, can range from a few centimetres to many metres, depending on the intensity and duration of weathering, episodes of soil deposition and erosion, and the patterns of landscape evolution. Nevertheless, in spite of this variability, soils have a unique structural characteristic that distinguishes them from mere earth materials and serves as a basis for their classification: a vertical sequence of layers produced by the combined actions of percolating waters and living organisms.

These layers are called horizons, and the full vertical sequence of horizons constitutes the soil profile (see the figure). Soil horizons are defined by features that reflect soil-forming processes. For instance, the uppermost soil layer (not including surface litter) is termed the A horizon. This is a weathered layer that contains an accumulation of humus (decomposed, dark-coloured, carbon-rich matter) and microbial biomass that is mixed with small-grained minerals to form aggregate structures.

Below A lies the B horizon. In mature soils this layer is characterized by an accumulation of clay (small particles less than 0.002 mm [0.00008 inch] in diameter) that has either been deposited out of percolating waters or precipitated by chemical processes involving dissolved products of weathering. Clay endows B horizons with an array of diverse structural features (blocks, columns, and prisms) formed from small clay particles that can be linked together in various configurations as the horizon evolves.

Below the A and B horizons is the C horizon, a zone of little or no humus accumulation or soil structure development. The C horizon often is composed of unconsolidated parent material from which the A and B horizons have formed. It lacks the characteristic features of the A and B horizons and may be either relatively unweathered or deeply weathered. At some depth below the A, B, and C horizons lies consolidated rock, which makes up the R horizon.

These simple letter designations are supplemented in two ways (see the table of soil horizon letter designations). First, two additional horizons are defined. Litter and decomposed organic matter (for example, plant and animal remains) that typically lie exposed on the land surface above the A horizon are given the designation O horizon, whereas the layer immediately below an A horizon that has been extensively leached (that is, slowly washed of certain contents by the action of percolating water) is given the separate designation E horizon, or zone of eluviation (from Latin ex, “out,” and lavere, “to wash”). The development of E horizons is favoured by high rainfall and sandy parent material, two factors that help to ensure extensive water percolation. The solid particles lost through leaching are deposited in the B horizon, which then can be regarded as a zone of illuviation (from Latin il, “in,” and lavere).

The combined A, E, B horizon sequence is called the solum (Latin: “floor”). The solum is the true seat of soil-forming processes and is the principal habitat for soil organisms. (Transitional layers, having intermediate properties, are designated with the two letters of the adjacent horizons, as shown in the table of soil horizon letter designations.)The second enhancement to soil horizon nomenclature (also shown in the table) is the use of lowercase suffixes to designate special features that are important to soil development. The most common of these suffixes are applied to B horizons: g to denote mottling caused by waterlogging, h to denote the illuvial accumulation of humus, k to denote carbonate mineral precipitates, o to denote residual metal oxides, s to denote the illuvial accumulation of metal oxides and humus, and t to denote the accumulation of clay.

Soils and global change Soils and climate have always been closely related. The predicted temperature increases due to global warming and the consequent change in rainfall patterns are expected to have a substantial impact on both soils and demographics. This anticipated climatic change is thought to be driven by the greenhouse effect—an increase in levels of certain trace gases in the atmosphere such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The conversion of land to agriculture, especially in the humid tropics, is an important contribution to greenhouse gas emissions. Some computer models predict that CH4 and N2O emissions will also be very important in future global change. About 70 percent of the CH4 and 90 percent of the N2O in the atmosphere are derived from soil processes. But soils can also function as repositories for these gases, and it is important to appreciate the complexity of the source-repository relationship. For example, the application of nitrogen-containing fertilizers reduces the ability of the soil to process CH4. Even the amount of nitrogen introduced into soil from acid rain on forests is sufficient to produce this effect. However, the extent of net emissions of CH4 and N2O and the microbial trade-off between the two gases are undetermined at the global scale.

Perhaps the most notable and pervasive role of soils in global change phenomena is the regulation of the CO2 budget. Carbon that is stored in terrestrial plants mainly through photosynthesis is called net primary production or NPP and is the dominant source of food, fuel, fibre, and feed for the entire population of the Earth. Approximately 55 billion metric tons (61 billion tons) of carbon are stored in this way each year worldwide, most of it in forests. About 800 million hectares (20 billion acres) of forestland have been lost since the dawn of civilization; this translates to about 6 billion metric tons of carbon per year less NPP than before land was cleared for agriculture and commerce. This estimated decrease in carbon storage can be compared to the 5–6 billion metric tons of carbon currently released per year by fossil fuel burning. One is left with the sobering conclusion that reforestation of the entire planet to primordial levels would have only a temporary counterbalancing effect on carbon release to the atmosphere from human consumption of natural resources.

Carbon in terrestrial biomass that is not used directly becomes carbon in litter (about 25 billion metric tons of carbon annually) and is eventually incorporated into soil humus. Soil respiration currently releases an average of 68 billion metric tons of this carbon back into the atmosphere. The natural cycling of carbon is directly and indirectly affected by land-use changes through deforestation, reforestation, wood products decomposition, and abandonment of agricultural land. The current estimate of carbon loss from all these changes averages about 1.7 billion metric tons per year worldwide, or about one-third the current loss from fossil fuel burning. This figure could as much as double in the first half of the 21st century if the rate of deforestation is not controlled. Reforestation, on the other hand, could actually reduce the current carbon loss by up to 10 percent without exorbitant demands on management practices.

Soil pollution. Xenobiotic chemicals. The presence of substances in soil that are not naturally produced by biological species is of great public concern. Many of these so-called xenobiotic (from Greek xenos, “stranger,” and bios, “life”) chemicals have been found to be carcinogens or may accumulate in the environment with toxic effects on ecosystems (see the table of major soil pollutants). Although human exposure to these substances is primarily through inhalation or drinking water, soils play an important role because they affect the mobility and biological impact of these toxins.

The abundance of xenobiotic compounds in soil has been increased dramatically by the accelerated rate of extraction of minerals and fossil fuels and by highly technological industrial processes. Most of the metals listed in the table were typically found at very low total concentrations in pristine waters—for this reason they often are referred to as trace metals. Rapid increases of trace metal concentrations in the environment are commonly coupled to the development of exploitative technologies. This kind of sudden change exposes the biosphere to a risk of destabilization, since organisms that developed under conditions with low concentrations of a metal present have not developed biochemical pathways capable of detoxifying that metal when it is present at high concentrations. The same line of reasoning applies to the organic toxic compounds listed in the table.

The mechanisms underlying the toxicity of xenobiotic compounds are not understood completely, but a consensus exists as to the importance of the following processes for the interactions of toxic metals with biological molecules: (1) displacement by a toxic metal of a nutrient mineral (for example, calcium) bound to a biomolecule, (2) complexation of a toxic metal with a biomolecule that effectively blocks the biomolecule from participating in the biochemistry of an organism, and (3) modification of the conformation of a biomolecule that is critical to its biochemical function. All of these mechanisms are related to complex formation between a toxic metal and a biomolecule. They suggest that strong complex-formers are more likely to induce toxicity by interfering with the normal chemistry of biomolecules.

Not all soil pollutants are xenobiotic compounds. Crop production problems in agriculture are encountered when excess salinity (salt accumulation) occurs in soils in arid climates where the rate of evaporation exceeds the rate of precipitation. As the soil dries, ions released by mineral weathering or introduced by saline groundwater tend to accumulate in the form of carbonate, sulfate, chloride, and clay minerals. Because all Na+ (sodium) and K+ (potassium) and many Ca2+ (calcium) and Mg2+ (magnesium) salts of chloride, sulfide, and carbonate are readily soluble, it is this set of metal ions that contributes most to soil salinity. At sufficiently high concentrations, the salts pose a toxicity hazard from Na+, HCO3- (bicarbonate) and Cl- (chloride) and interfere with water uptake by plants from soil. Toxicity from B (boron) is also common because of the accumulation of boron-containing minerals in arid soil environments.

The sustained use of a water resource for irrigating agricultural land in an arid region requires that the applied water not damage the soil environment. Irrigation waters are also salt solutions; depending on their particular source and postwithdrawal treatment, the particular salts present in irrigation water may not be compatible with the suite of minerals present in the soils. Crop utilization of water and fertilizers has the effect of concentrating salts in the soil; consequently, without careful management irrigated soils can become saline or develop toxicity. A widespread example of irrigation-induced toxicity hazard is NO3- (nitrate) accumulation in groundwater caused by the excess leaching of nitrogen fertilizer through agricultural soil. Human infants receiving high-nitrate groundwater as drinking water can contract methemoglobinemia (“blue baby syndrome”) because of the transformation of NO3- to toxic NO2- (nitrite) in the digestive tract. Costly groundwater treatment is currently the only remedy possible when this problem arises.

Soil microorganisms, particularly bacteria, have developed diverse means to use readily available substances as sources of carbon or energy. Microorganisms obtain their energy by transferring electrons biochemically from organic matter (or from certain inorganic compounds) to electron acceptors such as oxygen (O2) and other inorganic compounds. Therefore, they provide a significant pathway for decomposing xenobiotic compounds in soil by using them as raw materials in place of naturally occurring organic matter or electron acceptors, such as O, NO3- (nitrate), Mn4+ (manganese) or Fe3+ (iron) ions, and sulfate (SO42-). For instance, one species of bacteria might use the pollutant toluene, a solvent obtained from petroleum, as a carbon source, and naturally occurring Fe3+ might serve as a normal electron acceptor. Another species might use natural organic acids as a carbon source and selenium-containing pollutants as electron acceptors. Often, however, the ultimate decomposition of a contaminating xenobiotic compound requires a series of many chemical steps and several different species of microorganism. This is especially true for organic compounds that contain chlorine (Cl), such as chlorinated pesticides, chlorinated solvents, and polychlorinated biphenyls (PCBs; once used as lubricants and plasticizers). For example, the chlorinated herbicide atrazine is gradually degraded by aerobic microorganisms through a variety of pathways involving intermediate products. The complexity of the decomposition processes and the inherent toxicity of the pollutant compounds to the microorganisms themselves can lead to long residence times in soil, ranging from years to decades for toxic metals and chlorinated organic compounds.

Most of the metals that are major soil pollutants can form strong complexes with soil humus that significantly decrease the solubility of the metal and its movement toward groundwater. Humus can serve as a detoxification pathway by assuming the role taken by biomolecules in the metal toxicity mechanisms discussed above. Just as strong complex formation leads to irreversible metal association with a biomolecule and to the disruption of biochemical functions, so, too, can it lead to effective immobilization of toxic metals by soil humus—in particular, the humic substances. The very property of toxic metals that makes them so hazardous to organisms also makes them detoxifiable by humus in soil.

Pesticides exhibit a wide variety of molecular structures that permit an equally diverse array of mechanisms of binding to humus. The diversity of molecular structures and reactivities results in the production of a variety of aromatic compounds through partial decomposition of the pesticides by microbes. These intermediate compounds become incorporated into the molecular structure of humus by natural mechanisms, effectively reducing the threat of toxicity. The benefits of humus to soil fertility and detoxification have resulted in a growing interest in this remarkable substance and in the fragile A horizon it occupies.

TEXT 7

      MAPPING THE SOUL OF THE LAND

THE ECOPSYCHOLOGY OF PLACE

Christopher Castle

Christopher Castle, the arts editor of Ecopsychology On-Line and former editor of the Ecopsychology Newsletter, is an English painter, printmaker, and icon-maker whose work is represented in several collections, including the British Museum. His interest in ecological and indigenous art has led him to study sacred sites across Europe and in the American Southwest. He is also a composer who scores for the synthesizer from the computerized contours of landscape and of such natural objects as cellular forms, animal tracks, and stellar geometry. In 1997 he received a grant from the Marin County Arts Council to undertake the Marinography Mapping Project. Based upon the highly successful Common Ground Parish Maps Project in Great Britain, the Marinography Mapping Project is an extraordinary example of community-based art that expresses ecological values. Drawing upon oral history, local memory, personal stories, and indigenous lore collected from those who live in the area, the project seeks to configure a people’s cultural heritage into a map – in this case people in and around West Marin County in California where Castle resides. As director of the project, Castle organizes focus groups made up of school children, merchants, farmers and ranchers, senior citizens, native Americans, and other residents who provide the raw material from which local artists will create a permanent work that is, in effect, an emotional map. Because the project weaves together an intimate knowledge of place with deep personal feeling, it is a significant application of ecopsychology.

In one of his whimsical stories, Lewis Caroll, creator of Alice in Wonderland, came up with a humorous paradox about maps. One of his characters asks, “What do you consider the largest map that would really be useful?” – “About six inches to the mile.”

“Only six inches!” exclaimed Mein Herr. “We very soon got to six yards to the mile. Then we tried a hundred yards to the mile. And then came to the grandest idea of all! We actually made a map of the country, on a scale of a mile to the mile!”

“Have you used it much?” I enquired.

“It has never been spread out, yet,” said Mein Herr; “the farmers objected: they said it would cover the whole country and shut out the sunlight! So we now use the country itself, as its own map, and I assure you it does nearly as well.” From Sylvie and Bruno Concluded (The Man in the Moon)

But not even the map that was as big as the terrain itself would be able to capture the soul of the land. That requires a special kind of map. A community map.

I have designed the Marinography Mapping Projectto involve the community of West Marin County, California, in the process of discovering the natural, social and cultural ecology of our area through art and communication. The project intends to give individual local voices a chance to be heard telling their own stories of the place through images, dreams, memories, anecdotes, current perceptions, and visions for the future of the land. In this sense a map of this kind is related to earlier forms of cartography in which subjective perceptions and objective observation are featured with equal weight.

The area we are mapping is quite special in its location and its unusual combination of features. Tomales Bay, a long narrow inlet defined by the Can Andreas Fault, divides the mainland grassy hills of ranch land Marin County from the Point Reyes Peninsular, a roughly triangular form projecting into the Pacific and including forests of Bishop Pine on slopes going down to estuaries and sandy beaches. Flora, fauna, water and bird life abound.

This beautiful area is located within an hour’s drive from San Francisco. Most of the land is preserved as Point Reyes National Seashore and provides a unique resource as a get-away for the metropolitan area of the San Francisco Bay Area. Point Reyes Station provides the principal locus for the development of the project, which reaches out to include the small towns of Iverness, Olema and Marshall. Events and focus group meetings involving school children, seniors, farmers and various experts on the human and natural history of the area are being held to encourage people to join the adventure, to exchange stories and to make our first pictures. “Stories” in this case include positive and negative sides of the perception of the place, experiences involving the power of nature in people’s lives, memories of incidents at particular sites, delights, frustrations, irritations, demands, individual feelings, hopes, fears and wishes. My plan is to bring together these various cross-sections of our community to create maps that illuminate thoughts and feelings about the local environment.

The community map that will result from this process is not the usual topographical or land-use surveys, but rather a personal expression which tells people’s stories of how they see their neighbourhood and surrounding land. We are using visual art to map our experience of the bio-region of Tomales Bay, the waters and wetlands, the surrounding grassy hills, wooded valleys and streams, together with the Seashore lands and coast. The community of wild and domestic creatures, botanical species, even geological structures will also lend their voices to the mapping. As a way of engaging the senses as well as the intellect, we will not be using the ordinary paper or cardboard, but rather selecting natural materials from the area itself to provide much of the raw material for the map. This is one of our assignments for the schools. Children are bringing in native grasses and soil samples from various areas, so that the place itself – its colour, its odour, its texture – will literary be a part of the finished map. We are finding an immediate fascination and excitement displayed by the children when they see their own maps forming and beginning to communicate.

My hope is that the process of creating the final map will engender an artful awakening of the full ecological complexity of this area and an understanding of and respect for the rich resources we share. Mapping will bring intergenerational and inter-cultural groups, the native and immigrant communities, together for a common purpose that has deep environmental, social and political implications.

There are highly successful precedents for community mapping. Rural and urban communities in Great Britain have produced delightful, innovative maps which have galvanized their communities in creative ways. Foremost among these has been the Common Ground Parish Maps Project which began in the early 1980s.

I have designed the Marinography Mapping Project as a journey of discovery consisting of three main phases:

1. Meetings, interviews, field trips and preparatory drawings, with an exhibition of preparatory art works and documentation.

2. Creation of the finished map as mural and installation for a permanent display.

3.  Production of printed and website versions of the map.

Eventually, at the cumulation of the project, the core group of artists will coordinate the material as a mural-size map. This will be placed on permanent display in Point Reyes Station.

In a community map the voices of all sections of the population, elders, young ones, workers in different fields, different cultures are given opportunities to be heard. Unexpected views are exposed. Sometimes activism on an issue may be spurred or harmful environmental practices curtailed as the light of personal witness is shone upon them. Special sights, sounds, scents are often vivid keys to memories about places, unlocking forgotten details of a place and experience. Another kind of map might be based on smell, colour and sound, even taste, and certainly texture and temperature. I hope to reflect all these human possibilities in the Marinography Project. 

Section 3: Vocabulary exercises

№ 1

Translate into English:

1. За миллионы лет многие живые существа приспособились к естественным изменениям климата.

2. Однако, для живых существ значительно сложнее приспособиться к выбросам в окружающую среду вредных веществ, производимых человеком.

3. Температура Земли с каждым годом повышается, что, в конечном итоге, может оказаться чреватым губительными последствиями для человека.

4. По мере того, как планета будет нагреваться, уровень воды в океанах будет повышаться. и вода, заключенная в ледниках и полярных снегах, начнет таять.

5. Отравляющие газы становятся частью природного круговорота воды, они могут довольно далеко переноситься ветром, а затем выпадают на землю в виде кислотного дождя или снега.

6. С 1979 года в озоновом слое Земли существуют так называемые «дыры», которые появились сначала над Антарктидой, а затем над Арктикой.

7. Сегодня человек безгранично вмешивается в природу и пытается радикально изменить естественную среду обитания живых организмов для удовлетворения своих потребностей.

8. Вредное влияние экономической деятельности человека нарушает хрупкий баланс живых существ в их естественной среде.

9. Известно, что четверть мировой флоры находится на грани исчезновения.

10. Наиболее серьезной угрозой для растений является разрушение их естественной среды обитания. Это вырубка тропических лесов, осушение болотистых земель и превращение лугов в пахотные земли.

11. Деревья ребят для получения древесины или расчистки места для ферм и рудников. При этом вырубка лесов порождает немало будущих проблем, таких, как эрозия почвы, наводнения и засухи.

12. Законы о сохранении земель и контроль загрязнения могли бы способствовать их восстановлению.

№ 2

Translate into English:

1. Экологическая проблема является одной из наиболее актуальных нерешенных глобальных проблем современности.

2. Попытка превратить естественную среду в среду, подходящую для человека и отвечающую его потребностям, со временем превратилась в безграничное и неконтролируемое вмешательство в природу.

3. И вот сейчас, в начале 21 века, когда окружающая среда необратимо изменилась, мы вынуждены признать, что экономическая деятельность человека оказалась чревата губительными последствиями.

4. Пришло время оценить вред, нанесенный окружающей среде.

5. К сожалению, самая приблизительная оценка показывает, что на современном этапе компенсировать негативное влияние общества на окружающую среду едва ли представляется возможным.

6. Мы столкнулись с такой проблемой, как вымирание животных и растений в огромных масштабах.

7. Продолжительность жизни людей сокращается особенно интенсивно в последние 50 лет.

8. Истощение земных ресурсов, поднятие уровня мирового океана в результате глобального потепления, парниковый эффект, создающий своего рода барьер, не пропускающий тепловую энергию Земли в атмосферу, а также разрушение озонового слоя, вследствие которого вся жизнь на планете оказывается подверженной смертельному солнечному излучению, - лишь некоторые из проблем, требующих немедленного решения.

9. Поэтому сейчас, когда мы понимаем, что Земля подвержена разрушительному влиянию человека, нам важно осознать и острую необходимость изменить характер взаимодействия между человеком и природой.

10. А этому, несомненно, способствует строгое исполнение законов по охране природы и специально организованное экологическое образование и воспитание.

11. Причем важно, чтобы законы издавались не только на уровне правительства, но и реализовывались местными властями.

12. Что же касается экологического воспитания, то оно должно в первую очередь начинаться в семье.

13. А затем школа также должна учить нас, что не бесконтрольное вмешательство человека в природу, а оптимизация взаимодействия природы и общества обеспечат социальный и экономический прогресс общества. 

 

№ 3

Translate into English:

1. В процессе ядерного деления высвобождается огромное количество тепла, которое используется в ядерной энергетике.

2. На атомных электростанциях процесс ядерного деления контролируется таким образом, чтобы выделение энергии не сопровождалось взрывом.

3. Некоторые радиоактивные вещества, образующиеся в реакторе, остаются опасными на протяжении тысяч лет.

4. Ядерный реактор не взрывается подобно атомной бомбе, однако авария на атомной станции может произвести разрушительный эффект на большой территории.

5. Ядерная энергия является хорошим источником электричества на сотни тысяч лет, но вопрос в том, безопасный ли это источник.

6. Не поискать ли нам другие способы производства электроэнергии, или же выбрать такой стиль жизни, который не требует большого ее потребления?

7. Например, в отличие от других природных источников энергии, вода неисчерпаема.

8. Гидроэлектростанции часто строят на холмистых территориях. Обязательным условием является наличие природного резервуара, обеспечивающего запас воды для работы станции. Желательно также, чтобы климатические условия допускали большое количество осадков.

9. Энергия приливов – еще один важный источник энергии. К сожалению, время приливов неустойчиво, и поэтому достаточно сложно получать электроэнергию в нужное время.

10.  В отличие от теплоэлектростанций, аэрогенераторы не загрязняют атмосферу, однако трудно предугадать силу ветра.

11. Энергия солнца всегда являлась важным источником энергии. Солнечные элементы (solar cells) превращают энергию солнца непосредственно в электрическую энергию.

12. На самом деле, солнце могло бы полностью обеспечит нас необходимой энергией, если бы мы умели ее эффективно использовать.

 

 

№ 4

Translate into Russian