Ecological problems; Ecological problems - Topic in English. Ecological problems - current topic in English

In recent years the number of environmental problems has increased greatly. One of the most dangerous problems for our planet is global warming which means that most climates all over the world are changing and getting warmer. It happens because we burn too much petrol resources, such as oil and coal, and the Earth heats up. This process can cause melting of the polar ice and the sea level rising in the future. If the climate changes there will be floods, heavy storms or severe droughts in different areas of the world. Cutting down on exhaust fumes from vehicles could help solve this serious problem.

Our planet is overpopulated, that's why we are using up our natural resources – they are not endless. So the scientists have started looking for some alternate forms of energy such as water, wind, sunlight and even tides. These resources are clean, natural and unlimited. I'm glad that modern automobile industries make hybrids which use electric or solar energy instead of petrol. It would definitely help protect our environment from pollution.

There are different kinds of environmental pollution: air pollution, water pollution, land pollution. Sadly, not all human beings realize or admit that we are the ones who cause these problems and we should be the first to stop them and protect our environment. Because of the industrial revolution the air is polluted with awful chemicals; seas and oceans are poisoned with oil spills. Many rare species of flora and fauna are threatened with extinction.

We should be proud to live on our wonderful planet and understand that the consequences of pollution might be terrible and affect us and our children later. We should start recycling things made of glass, paper, plastic and aluminum. We should stop smoking and plant as many trees as we can because they can give us more oxygen. We need to drive less and use public transport in order to reduce fuel burning. We are responsible for the situation.

Environmental issues

In recent years, the number of environmental problems has increased greatly. One of the most dangerous problems for our planet is global warming, which means climate change around the world and its warming. This is because we are burning too many fuel resources such as oil and coal and the Earth is warming up. This process could lead to the melting of polar ice and future sea level rise. If the climate changes, there will be floods, severe storms or severe droughts in different parts of the world. Reducing vehicle exhaust emissions could help alleviate this serious problem.

Our planet is overpopulated, so we use our natural resources to the limit - they are not endless. So scientists began to look for alternative forms of energy, such as water, wind, sunlight, and even tides. These springs are pure, natural and infinite. I'm glad the modern auto industry is turning out hybrids that use electricity or solar energy instead of gasoline. This will definitely help protect our environment from pollution.

There are different types of environmental pollution: air, water and soil pollution. Unfortunately, not all people realize or admit that we are the ones who create these problems, and we should be the first to stop them and protect our environment. Due to the industrial revolution, the air is polluted with terrible chemicals; the seas and oceans are poisoned by oil spills. Many rare species of flora and fauna are under threat of extinction.

We need to be proud to live on our wonderful planet and understand that the effects of pollution can be dire and affect us and our children later. We need to recycle glass, paper, plastic and aluminium. We need to stop smoking and plant as many trees as possible so that they produce more oxygen for us. We should drive less and try to use public transport to reduce the amount of fuel we burn. We are responsible for the situation.

Recently, the problem of environmental pollution has become acute. It is raised both in schools and universities. In particular, they are asked to write an essay on the topic of environmental protection in English. So English language topics on the topic ecology very popular.

Topic Ecology problems

Since ancient times Nature has served man, being the source of his life. For thousands of years people lived in harmony with the environment and it seemed to them that natural riches were unlimited. But with the development of civilization man's interference in nature began to increase.

Every year world industry pollutes the atmosphere with about 1000 million tons of dust and other things. As a result some rare species of animals, birds, fish and plants disappear forever. Many cities suffer from smog.

Large cities with thousands of smoky industrial enterprises appear all over the world today. The by-products of their activity pollute the air we breathe, the water we drink, the land we grow vegetables.

The pollution of air and the world’s ocean, destruction of the ozone layer is the result of man’s careless interaction with nature. Environmental protection is of a universal concern. That is why serious measures to create a system of ecological security should be taken.

Some progress has already been made in this direction. As many as 159 countries - members of the UNO - have set up environmental protection agencies. Numerous conferences have been held by these agencies to discuss problems facing ecologically poor regions including the Aral Sea, the South Urals, Kuzbass, Donbass, Semipalatinsk and Chernobyl. An international environmental research center has been set up on Lake Baikal. The international organization Greenpeace is also doing much to preserve the environment.

But these are only the initial steps and they must be carried onward to protect nature, to save life on the planet not only for the present but also for the future generations.

But these are only the initial steps and they should be more tied to the protection of nature in order to preserve life on the planet, not only for the present, but also for the future generation.

Topic translation into Russian

Ecological problems

Since ancient times, nature has extended human life by providing it with resources for life. For thousands of years, people lived in harmony with the environment and it seemed to them that the riches of nature are inexhaustible. But with the advent of human civilization, cataclysms in nature began to increase.

Every year, the global industry emits about 1,000 million tons of dust and other substances into the atmosphere. As a result, some rare species of animals, birds, fish and animals have disappeared forever. Many cities suffer from smog.

Large cities with thousands of smoking industries are represented on a global scale in large numbers. The by-products they produce pollute the air we breathe, the water we drink, the land we grow vegetables on.

Pollution of the air and the oceans, the destruction of the ozone layer is the result of human indifference towards nature. The environment is protected by the worldwide association. That is why serious measures should be taken to create a system of environmental safety.

Some progress has already been made in this regard. Thus, 159 UNO member countries have created an environmental protection agency. Numerous conferences are held by these agencies and they discuss the problems faced by environmentally distressed regions, including the Aral Sea, the South Urals, Kuzbass, Semipalatinsk and Chernobyl. An international environmental study is being conducted on Lake Baikal. The international organization Greenpeace is also doing a lot to protect the environment.

Dear visitors, are you concerned about environmental issues? And how close are ecology problems to you?

Do you think global pollution needs to be stopped?

Level B. Other.

Ecology

Some people say that nowadays the problem of ecology is becoming more and more vital. But others consider that it is not important for people with modern technologies. And who is right? I am for the former point o view, and now I will try to explain why.

Firstly, there are a lot of big cities in the world such as New York, Tokyo, Beijing, and Moscow. These cities pollute a lot. There are some kinds of pollution: water pollution, air pollution, and nuclear pollution. We breathe dirty air, drink dirty water, and eat dirty fruits and vegetables. So it harms our health. Secondly, there are a lot of nuclear stations all over the world such as Chernobyl or Fukushima, which became dangerous objects because of radiation.
People who worked at these stations were not careful. So these stations are destroyed now. They are polluting a big territory. Thirdly, our world needs much fuel for various machines, technologies, various branches of science and everyday life. And the extraction of minerals harms nature and changes the landscape around the place of extraction.

But some people think that nowadays we have a lot of brands - new technologies that will help us in the future. They say that these technologies will help us with hunger, unemployment, dangerous kinds of diseases such as plague and cancer. With the help of nanotechnologies people will get new materials, which can be useful for the army, medicine, science. With a great technological progress the humanity will conquer space. All in all, people will defeat death.

I absolutely disagree with these people. Of course, it would be a great success for humanity. But these "dreams" need a lot of recourses which are not endless. And it is a long process to invent all these things and spread them all over the world.

In conclusion, I would like to stress that our world is very fragile, and we should take care of it because we are a part of this world. Without beautiful nature, useful plants, and animals humanity will die out. Don't you agree with me?

Ecology

Some people say that nowadays the problem of ecology is becoming more and more important. But others believe that it is not important for people with modern technology. And who is right? I am for the first point of view, and now I will try to explain why.

First, there are many big cities in the world such as New York, Tokyo, Beijing and Moscow. These cities pollute a lot. There are some types of pollution: water pollution, air pollution, and nuclear pollution. We breathe dirty air, drink dirty water, and eat dirty fruits and vegetables. So it's bad for our health. Secondly, there are many nuclear plants all over the world, such as Chernobyl or Fukushima, which have become dangerous objects due to radiation. The people who worked at these stations were not careful. Thus, these stations are now destroyed. They pollute a large area. Thirdly, our world needs a lot of fuel for various machines, technologies, various branches of science and everyday life. Mining damages nature and changes the landscape around the mining site.

But some people think that we currently have a lot of innovations - new technologies that will help us in the future. They say that these technologies will help us with hunger, unemployment, dangerous types of diseases such as plague and cancer. With the help of nanotechnologies, people will receive new materials that can be useful for the army, medicine, and science. With great technological progress, humanity will master space. In the end, people will conquer death.

I absolutely disagree with these people. Of course, this would be a great success for humanity. But for these "dreams" you need a lot of resources, which are not endless. And it's a long process to invent all these things and distribute them all over the world.

In conclusion, I would like to emphasize that our world is very fragile, and we must take care of it, because we are part of this world. Without beautiful nature, useful plants and animals, humanity will die out. Don't you agree with me?

M.N. Makeeva, L.P. Tsilenko, A.A. Gvozdeva MODERN ECOLOGICAL PROBLEMS TSTU Publishing House Ministry of Education and Science of the Russian Federation Tambov State Technical University M.N. Makeeva, L.P. Tsilenko, A.A. Gvozdeva MODERN ENVIRONMENTAL PROBLEMS Collection of texts in English for students of non-linguistic universities Tambov Publisher TSTU 2004 Bortnikova C56 Modern environmental problems: Collection of texts in English / Ed.-ed.: M.N. Makeeva, L.P. Tsilenko, A.A. Gvozdev. Tambov: Tambov Publishing House. state tech. un-ta, 2004. 96 p. This collection is a book to read in English for students of non-linguistic universities. The proposed authentic texts meet the dynamics of modern scientific and technological progress, the specifics of the specialties studied at the university, as well as the requirements of the English language program for students of higher educational institutions. UDC 802.0(076) BBK SH13(An)ya923 © Tambov State Technical University (TSTU), 2004 Educational publication MODERN ENVIRONMENTAL PROBLEMS Collection of texts in English Compiled by: Makeeva Marina Nikolaevna, Tsilenko Lyubov Petrovna, Gvozdeva Anna Anatolyevna Editor T.M. . Glinkina Computer prototyping E.V. Ship signed 18.06.04 Format 60 × 84 / 16. Offset paper. Offset printing Typeface Times New Roman. Volume: 5.58 arb. oven l.; 5.5 ed. l. Circulation 80 copies. P. 440M Publishing and Printing Center of the Tambov State Technical University, 392000, Tambov, Sovetskaya, 106, room 14 ECOLOGY Ecology is the study of the relationship of plants and animals with their physical and biological environ-ment. The physical environment includes light and heat or solar radiation, moisture, wind, oxygen, carbon dioxide, nutrients in soil, water, and atmosphere. The biological environment includes organisms of the same kind as well as other plants and animals. Because of the diverse approaches required to study organisms in their environment, ecology draws upon such fields as climatology, hydrology, oceanography, physics, chemistry, geology, and soil analysis. To study the relationships between organisms, ecology also involves such disparate sciences as animal behavior, taxonomy, physiology, and mathematics. An increased public awareness of environmental problems has made ecology a common but often misused word. It is confused with environmental programs and environmental science. Although the field is a distinct scientific discipline, ecology does indeed contribute to the study and understanding of environmental problems. The term "ecology" was introduced by the German biologist Ernst Heinrich Haeckel in 1866; it is derived from the Greek "oikos" ("household"), sharing the same root word as "economics". Thus, the term implies the study of the economy of nature. Modern ecology, in part, began with Charles Darwin. In developing his theory of evolution, Darwin stressed the adaptation of organisms to their environment through natural selection. Also making important contributions were plant geographers, such as Alexander von Humboldt, who were deeply interested in the "how" and "why" of vegetation distribution around the world. The thin mantle of life that covers the earth is called the biosphere. Several approaches are used to classify its regions. BIOMES The broad units of vegetation are called "plant formations" by European ecologists and "biomes" by North American ecologists. The major difference between the two terms is that "biomes" include associated animal life. Major biomes, however, go by the name of the dominant forms of plant life. Influenced by latitude, elevation, and associated moisture and temperature regimes, terrestrial biomes vary geographically from the tropics through the arctic and include various types of forest, grassland, shrub land, and desert. These biomes also include their associated freshwater communities: streams, lakes, ponds, and wetlands. Marine environments, also considered biomes by some ecologists, comprise the open ocean, littoral (shallow water) regions, benthic (bottom) regions, rocky shores, sandy shores, estuaries, and associated tidal marshes. ECOSYSTEMS A more useful way of looking at the terrestrial and aquatic landscapes is to view them as ecosystems, a word coined in 1935 by the British plant ecologist Sir Arthur George Tansley to stress the concept of each locale or habitat as an integrated whole. A system is a collection of interdependent parts that function as a unit and involve inputs and outputs. The major parts of an ecosystem are the producers (green plants), the consumers (herbivores and carnivores), the decomposers (fungi and bacteria), and the nonliving, or abiotic, components, consisting of dead organic matter and nutrients in the soil and water. Inputs into the ecosystem are solar energy, water, oxygen, carbon dioxide, nitrogen, and other elements and compounds. Outputs from the ecosystem include water, oxygen, carbon dioxide, nutrient losses, and the heat released in cellular respiration, or heat of respiration. The major driving force is solar energy. ENERGY AND NUTRIENTS Ecosystems function with energy flowing in one direction from the sun, and through nutrients, which are continuously recycled. Light energy is used by plants, which, by the process of photosynthesis, convert it to chemical energy in the form of carbohydrates and other carbon compounds. This energy is then transferred through the ecosystem by a series of steps that involve eating and being eaten, or what is called a food web. Each step in the transfer of energy involves several trophic, or feeding, levels: plants, herbivores (plant eaters), two or three levels of carnivores (meat eaters), and decomposers. Only a fraction of the energy fixed by plants follows this pathway, known as the grazing food web. Plant and animal matter not used in the grazing food chain, such as fallen leaves, twigs, roots, tree trunks, and the dead bodies of animals, support the decomposer food web. Bacteria, fungi, and animals that feed on dead material become the energy source for higher trophic levels that tie into the grazing food web. In this way, nature makes maximum use of energy originally fixed by plants. The number of trophic levels is limited in both types of food webs, because at each transfer a great deal of energy is lost (such as heat of respiration) and is no longer usable or transferable to the next trophic level. Thus, each trophic level contains less energy than the trophic level supporting it. For this reason, as an example, deer or caribou (herbivores) are more abundant than wolves (carnivores). Energy flow fuels the biogeochemical, or nutrient, cycles. The cycling of nutrients begins with their release from organic matter by weathering and decomposition in a form that can be picked up by plants. Plants in-corporate nutrients available in soil and water and store them in their tissues. The nutrients are transferred from one trophic level to another through the food web. Because most plants and animals go uneaten, nutrients contained in their tissues, after passing through the decomposer food web, are ultimately released by bacterial and fungal decomposition, a process that reduces complex organic compounds into simple inorganic compounds available for reuse by plants. IMBALANCES Within an ecosystem, nutrients are cycled internally. But there are leakages or outputs, and these must be balanced by inputs, or the ecosystem will fail to function. Nutrient inputs to the system come from weathering of rocks, from windblown dust, and from precipitation, which can carry material great distances. Varying quantities of nutrients are carried from terrestrial ecosystems by the movement of water and deposited in aquatic ecosystems and associated lowlands. Erosion and the harvesting of timber and crops remove considerable quan- tities of nutrients that must be replaced. The failure to do so results in an impoverishment of the ecosystem. This is why agricultural lands must be fertilized. If inputs of any nutrient greatly exceed outputs, the nutrient cycle in the ecosystem becomes stressed or overloaded, resulting in pollution. Pollution can be considered an input of nutrients exceeding the capability of the ecosystem to process them. Nutrients eroded and leached from agricultural lands, along with sewage and industrial wastes accumulated from urban areas, all drain into streams, rivers, lakes, and estuaries. These pollutants destroy plants and animals that cannot tolerate their presence or the changed environmental conditions caused by them; at the same time, they favor a few organisms more tolerant to changed conditions. Thus, precipitation filled with sulfur dioxide and oxides of nitrogen from industrial areas converts to weak sulfuric and nitric acids, known as acid rain, and falls on large areas of terrestrial and aquatic ecosystems. This upsets acid- base relations in some ecosystems, killing fish and aquatic invertebrates, and increasing soil acidity, which reduces forest growth in northern and other ecosystems that lack limestone to neutralize the acid. POPULATIONS AND COMMUNITIES The functional units of an ecosystem are the populations of organisms through which energy and nutrients move. A population is a group of interbreeding organisms of the same kind living in the same place at the same time. Groups of populations within an ecosystem interact in various ways. These interdependent populations of plants and animals make up the community, which encompasses the biotic portion of the ecosystem. DIVERSITY The community has certain attributes, among them dominance and species diversity. Dominance results when one or several species control the environmental conditions that influence the associated species. In a forest, for example, the dominant species may be one or more species of trees, such as oak or spruce; in a marine community, the dominant organisms are frequently animals such as mussels or oysters. Dominance can influence diversity of species in a community because diversity involves not only the number of species in a community, but also how numbers of individual species are apportioned. The physical nature of a community is evidenced by layering, or stratification. In terrestrial communities, stratification is influenced by the growth form of the plants. Simple communities such as grasslands, with little vertical stratification, usually consist of two layers, the ground layer and the herbaceous layer. A forest has up to six layers: ground, herbaceous, low shrub, low tree and high shrub, lower canopy, and upper canopy. These strata influence the physical environment and diversity of habitats for wildlife. Vertical stratification of life in aquatic communities, by contrast, is influenced mostly by physical conditions: depth, light, temperature, pressure, salinity, oxygen, and carbon dioxide. HABITAT AND NICHE The community provides the habitat – the place where particular plants or animals live. Within the habitat, organisms occupy different niches. A niche is the functional role of a species in a community – that is, its occupation, or how it earns its living. For example, the scarlet tanager lives in a deciduous forest habitat. Its niche, in part, is gleaning insects from the canopy foliage. The more a community is stratified, the more finely the habitat is divided into additional niches. ENVIRONMENT Environment comprises all of the external factors affecting an organism. These factors may be other living organisms (biotic factors) or nonliving variables (abiotic factors), such as temperature, rainfall, day length, wind, and ocean currents. The interactions of organisms with biotic and abiotic factors form an ecosystem. Even minute changes in any one factor in an ecosystem can influence whether or not a particular plant or animal species will be successful in its environment. Organisms and their environment constantly interact, and both are changed by this interaction. Like all other living creatures, humans have clearly changed their environment, but they have done so generally on a grander scale than have all other species. Some of these human-induced changes – such as the destruction of the world’s tropical rain forests to create farms or grazing land for cattle – have led to altered climate patterns. In turn, altered climate patterns have changed the way animals and plants are distributed in different ecosystems. Scientists study the long-term consequences of human actions on the environment, while environmentalists-professionals in various fields, as well as concerned citizens-advocate ways to lessen the impact of human activity on the natural world. UNDERSTANDING THE ENVIRONMENT The science of ecology attempts to explain why plants and animals live where they do and why their populations are the sizes they are. Understanding the distribution and population size of organisms helps scientists evaluate the health of the environment. In 1840 German chemist, Justus von Liebig first proposed that populations could not grow indefinitely, a basic principle now known as the Law of the Minimum. Biotic and abiotic factors, singly or in combination, ultimately limit the size that any population may attain. This size limit, known as a population’s carrying capacity, occurs when needed resources, such as food, breeding sites, and water, are in short supply. For example, the amount of nutrients in soil influences the amount of wheat that grows on a farm. If just one soil nutrient, such as nitrogen, is missing or below optimal levels, fewer healthy wheat plants will grow. Either population size or distribution may also be affected, directly or indirectly, by the way species in an ecosystem interact with one another. In an experiment performed in the late 1960s in the rocky tidal zone along the Pacific Coast of the United States, American ecologist Robert Paine studied an area that contained 15 species of invertebrates, including starfish, mussels, limpets, barnacles, and chitons. Paine found that in this eco- system one species of starfish preyed heavily on a species of mussel, preventing that mussel population from multiplying and monopolizing space in the tidal zone. When Paine removed the starfish from the area, he found that the mussel population quickly increased in size, crowding out most other organisms from rock surfaces. The number of invertebrate species in the ecosystem soon dropped to eight species. Paine additional concluded that the loss of just one species, the starfish, indirectly led to the loss of an six species and a transformation of the ecosystem. Typically, the species that coexist in ecosystems have evolved together for many generations. These populations have established balanced interactions with each other that enable all populations in the area to remain relatively stable. Occasionally, however, natural or human-made disruptions occur that have unforeseen consequences to populations in an ecosystem. For example, 17th-century sailors routinely introduced goats to isolated oceanic islands, intending for the goats to roam freely and serve as a source of meat when the sailors returned to the islands during future voyages. As non-native species free from all natural predators, the goats thrived and, in the process, overgrazed many of the islands. With a change in plant composition, many of the native animal species on the islands were driven to extinction. A simple action, the introduction of goats to an island, yielded many changes in the island ecosystem, demonstrating that all members of a community are closely interconnected. To better understand the impact of natural and human disruptions on the Earth, in 1991, the National Aeronautics and Space Administration (NASA) began to use artificial satellites to study global change. NASA’s undertaking, called Earth Science Enterprise, and is a part of an international effort linking numerous satellites into a single Earth Observing System (EOS). EOS collects information about the interactions occurring in the atmosphere, on land, and in the oceans, and these data help scientists and lawmakers make sound environ- mental policy decisions. FACTORS THREATENING THE ENVIRONMENT The problems facing the environment are vast and diverse. Global warming, the depletion of the ozone layer in the atmosphere, and destruction of the world’s rain forests are just some of the problems that many scientists believe will reach critical proportions in the coming decades. All of these problems will be directly affected by the size of the human population. POPULATION GROWTH Human population growth is at the root of virtually all of the world's environmental problems. Although the growth rate of the world's population has slowed slightly since the 1990s, the world's population increases by about 77 million human beings each year. As the number of people increases, crowding generates pollution, destroys more habitats, and uses up additional natural resources. The Population Division of the United Nations (UN) predicts that the world's population will increase from 6.23 billion people in 2000 to 9.3 billion people in 2050. The UN estimates that the population will stabilize at more than 11 billion in 2200. Other experts predict that numbers will continue to rise into the foreseeable future, to as many as 19 billion people by the year 2200. Although rates of population increase are now much slower in the developed world than in the developing world, it would be a mistake to assume that population growth is primarily a problem of developing countries. In fact, because larger amounts of resources per person are used in developed nations, each individual from the developed world has a much greater environmental impact than does a person from a developing country. Conservation strategies that would not significantly alter lifestyles but that would greatly lessen environmental impact are essential in the developed world. In the developing world, meanwhile, the most important factors necessary to lower population growth rates are democracy and social justice. Studies show that population growth rates have fallen in developing areas where several social conditions exist. In these areas, literacy rates have increased and women receive economic status equal to that of men, enabling women to hold jobs and own property. In addition, birth control information in these areas is more widely available, and women are free to make their own reproductive decisions. GLOBAL WARMING Like the glass panes in a greenhouse, certain gases in the Earth's atmosphere permit the Sun's radiation to heat Earth. At the same time, these gases retard the escape into space of the infrared energy radiated back out by Earth. This process is referred to as the greenhouse effect. These gases, primarily carbon dioxide, methane, nitrous oxide, and water vapor, insulate Earth’s surface, helping to maintain warm temperatures. Without these gases, Earth would be a frozen planet with an average temperature of about -18 °C (about 0 °F) instead of a comfortable 15 °C (59 °F). If the concentration of these gases rises, they trap more heat within the atmosphere, causing worldwide temperatures to rise. Within the last century, the amount of carbon dioxide in the atmosphere has increased dramatically, largely because people burn vast amounts of fossil fuels – coal and petroleum and its derivatives. Average global temperature also has increased – by about 0.6 Celsius degrees (1 Fahrenheit degree) within the past century. At- mospheric scientists have found that at least half of that temperature increase can be attributed to human activity. They predict that unless dramatic action is taken, global temperature will continue to rise by 1.4 to 5.8 Celsius degrees (2.5 to 10.4 Fahrenheit degrees) over the next century. Although such an increase may not seem like a great difference, during the last ice age the global temperature was only 2.2 Celsius degrees (4 Fahrenheit degrees) cooler than it is presently. The consequences of such a modest increase in temperature may be devastating. Already scientists have detected a 40 percent reduction in the average thickness of Arctic ice. Other problems that may develop include a rise in sea levels that will completely inundate a number of low-lying island nations and flood many coastal cities, such as New York and Miami. Many plant and animal species will probably be driven into extinction, agriculture will be severely disrupted in many regions, and the frequency of severe hurricanes and droughts will likely increase. DEPLETION OF THE OZONE LAYER The ozone layer, a thin band in the stratosphere (layer of the upper atmosphere), serves to shield Earth from the Sun's harmful ultraviolet rays. In the 1970s, scientists discovered that chlorofluorocarbons (CFCs)- chemicals used in refrigeration, air-conditioning systems, cleaning solvents, and aerosol sprays-destroy the ozone layer. CFCs release chlorine into the atmosphere; chlorine, in turn, breaks down ozone molecules. Be- cause chlorine is not affected by its interaction with ozone, each chlorine molecule has the ability to destroy a large amount of ozone for an extended period of time. The consequences of continued depletion of the ozone layer would be dramatic. Increased ultraviolet radiation would lead to a growing number of skin cancers and cataracts and also reduce the ability of immune systems to respond to infection. Additionally, growth of the world's oceanic plankton, the base of most marine food chains, would decline. Plankton contains photosynthetic organisms that break down carbon dioxide. If plankton populations decline, it may lead to increased carbon dioxide levels in the atmosphere and thus to global warming. Recent studies suggest that global warming, in turn, may increase the amount of ozone de- stroyed. Even if the manufacture of CFCs is immediately banned, the chlorine already released into the atmos- sphere will continue to destroy the ozone layer for many decades. In 1987, an international pact called the Montreal Protocol on Substances that Deplete the Ozone Layer set specific targets for all nations to achieve in order to reduce emissions of chemicals responsible for the destruction of the ozone layer. Many people had hoped that this treaty would cause ozone loss to peak and begin to de- cline by the year 2000. In fact, in the fall of 2000, the hole in the ozone layer over Antarctica was the largest ever recorded. The hole the following year was slightly smaller, leading some to believe that the depletion of ozone had stabilized. Even if the most stringent prohibitions against CFCs are implemented, however, scientists expect that it will take at least 50 more years for the hole over Antarctica to close completely. HABITAT DESTRUCTION AND SPECIES EXTINCTION Plant and animal species are dying out at an unprecedented rate. Estimates range that from 4,000 to as many as 50,000 species per year become extinct. The leading cause of extinction is habitat destruction, particu- larly of the world’s richest ecosystems-tropical rain forests and coral reefs. If the world's rain forests continue to be cut down at the current rate, they may completely disappear by the year 2030. In addition, if the world's population continues to grow at its present rate and puts even more pressure on these habitats, they might well be destroyed sooner. AIR POLLUTION A significant portion of industry and transportation burns fossil fuels, such as gasoline. When these fuels burn, chemicals and particulate matter are released into the atmosphere. Although a vast number of substances contribute to air pollution, the most common air pollutants contain carbon, sulfur, and nitrogen. These chemi- cals interact with one another and with ultraviolet radiation in sunlight in dangerous ways. Smog, usually found in urban areas with large numbers of automobiles, forms when nitrogen oxides react with hydrocarbons in the air to produce aldehydes and ketones. could cause serious health problems. Acid rain forms when sulfur dioxide and nitrous oxide transform into sulfuric acid and nitric acid in the atmosphere and come back to Earth in precipitation. Acid rain has made numerous lakes so acidic that they no longer support fish populations. Acid rain is also responsible for the decline of many forest ecosystems world-wide, including Germany’s Black Forest and forests throughout the eastern United States. WATER POLLUTION Estimates suggest that nearly 1.5 billion people worldwide lack safe drinking water and that at least 5 million deaths per year can be attributed to waterborne diseases. Water pollution may come from point sources or nonpoint sources. Point sources discharge pollutants from specific locations, such as factories, sewage treatment plants, and oil tankers. The technology exists to monitor and regulate point sources of pollution, although in some areas this occurs only sporadically. Pollution from nonpoint sources occurs when rainfall or snowmelt moves over and through the ground. As the runoff moves, it picks up and carries away pollutants, such as pesticides and fertilizers, depositing the pollutants into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. Pollution arising from nonpoint sources accounts for a majority of the contaminants in streams and lakes. With almost 80 percent of the planet covered by oceans, people have long acted as if those bodies of water could serve as a limitless dumping ground for wastes. However, raw sewage, garbage, and oil spills have begun to overwhelm the diluting capabilities of the oceans, and most coastal waters are now polluted, threatening marine wildlife. Beaches around the world close regularly, often because the surrounding waters contain high lev- els of bacteria from sewage disposal. HOW ECOSYSTEMS WORK. ECOSYSTEM MANAGEMENT Ecosystem comprises organisms living in a particular environment, such as a forest or a coral reef, and the physical parts of the environment that affect them. The term ecosystem was coined in 1935 by the British ecologist Sir Arthur George Tansley, who described natural systems in "constant interchange" among their living and nonliving parts. The ecosystem concept fits into an ordered view of nature that was developed by scientists to simplify the study of the relationships between organisms and their physical environment, a field known as ecology. At the top of the hierarchy is the planet's entire living environment, known as the biosphere. Within this biosphere are several large categories of living communities known as biomes that are usually characterized by their dominant vegetation, such as grasslands, tropical forests, or deserts. The biomes are in turn made up of ecosystems. The living, or biotic, parts of an ecosystem, such as the plants, animals, and bacteria found in soil, are known as a community. The physical surroundings, or abiotic components, such as the minerals found in the soil, are known as the environment or habitat. Any given place may have several different ecosystems that vary in size and complexity. A tropical island, for example, may have a rain forest ecosystem that covers hundreds of square miles, a mangrove swamp eco- system along the coast, and an underwater coral reef ecosystem. No matter how the size or complexity of an ecosystem is characterized, all ecosystems exhibit a constant exchange of matter and energy between the biotic and abiotic community. Ecosystem components are so interconnected that a change in any one component of an ecosystem will cause subsequent changes throughout the system. The living portion of an ecosystem is best described in terms of feeding levels known as trophic levels. Green plants make up the first trophic level and are known as primary producers. Plants are able to convert energy from the sun into food in a process known as photosynthesis. In the second trophic level, the primary consumers – known as herbivores – are animals and insects that obtain their energy solely by eating the green plants. The third trophic level is composed of the secondary consumers, flesh-eating or carnivorous animals that feed on herbivores. At the fourth level are the tertiary consumers, carnivores that feed on other carnivores. Finally, the fifth trophic level consists of the decomposers, organisms such as fungi and bacteria that break down dead or dying matter into nutrients that can be used again. Some or all of these trophic levels combine to form what is known as a food web, the ecosystem’s mechanism for circulating and recycling energy and materials. For example, in an aquatic ecosystem algae and other aquatic plants use sunlight to produce energy in the form of carbohydrates. Primary consumers such as insects and small fish may feed on some of this plant matter, and are in turn eaten by secondary consumers, such as salmon. A brown bear may play the role of the tertiary consumer by catching and eating salmon. Bacteria and fungi may then feed upon and decompose the salmon carcass left behind by the bear, enabling the valuable nonliving components of the ecosystem, such as chemical nutrients, to leach back into the soil and water, where they can be absorbed by the roots of plants. In this way, nutrients and the energy that green plants derive from sunlight are efficiently transferred and recycled throughout the ecosystem. In addition to the exchange of energy, ecosystems are characterized by several other cycles. Elements such as carbon and nitrogen travel throughout the biotic and abiotic components of an ecosystem in processes known as nutrient cycles. For example, nitrogen traveling in the air may be snatched by tree-dwelling, or epiphytic, lichen that converts it to a form useful to plants. When rain drips through the lichen and falls to the ground, or the lichen itself falls to the forest floor, the nitrogen from the raindrops or the lichen is leached into the soil to be used by plants and trees. Another process important to ecosystems is the water cycle, the movement of water from ocean to atmosphere, to land and eventually back to the ocean. An ecosystem such as a forest or wetland plays a significant role in this cycle by storing, releasing, or filtering the water as it passes through the system. Every ecosystem is also characterized by a disturbance cycle, a regular cycle of events such as fires, storms, floods, and landslides that keeps the ecosystem in a constant state of change and adaptation. Some specialties even depend on the disturbance cycle for survival or reproduction. For example, longleaf pine forests depend on frequent low-intensity fires for reproduction. The cones of the trees, which contain the reproductive structures, are sealed shut with a resin that melts away to release the seeds only under high heat. ECOSYSTEM MANAGEMENT Humans benefit from these smooth-functioning ecosystems in many ways. Healthy forests, streams, and wetlands contribute to clean air and clean water by trapping fast-moving air and water, enabling impurities to settle out or be converted to harmless compounds by plants or soil. The diversity of organisms, or biodiversity, in an ecosystem provides essential foods, medicines, and other materials. But as human populations increase and their encroachment on natural habitats expand, humans are having detrimental effects on the very ecosystems on which they depend. The survival of natural ecosystems around the world is threatened by many human activities: bulldozing wetlands and clear-cutting forests – the systematic cutting of all trees in a specific area – to make room for new housing and agricultural land; damming rivers to harness the energy for electricity and water for irrigation; and polluting the air, soil, and water. Many organizations and government agencies have adopted a new approach to managing natural resources – naturally occurring materials that have economic or cultural value, such as commercial fisheries, timber, and water, in order to prevent their catastrophic depletion. This strategy, known as ecosystem management, treats resources as interdependent ecosystems rather than simply commodities to be extracted. Using advances in the study of ecology to protect the biodiversity of an ecosystem, ecosystem management encourages practices that enable humans to obtain the necessary resources using methods that protect the whole ecosystem. Be- cause regional economic prosperity may be linked to ecosystem health, the needs of the human community are also considered. Ecosystem management often requires special measures to protect threatened or endangered species that play key roles in the ecosystem. In the commercial shrimp trawling industry, for example, ecosystem management techniques protect loggerhead sea turtles. In the last thirty years, populations of loggerhead turtles on the southeastern coasts of the United States have been declining at alarming rates due to beach development and the ensuing erosion, bright lights, and traffic, which make it nearly impossible for female turtles to build nests on beaches. At sea, loggerheads are threatened by oil spills and plastic debris, offshore dredging, injury from boat propellers, and being caught in fishing nets and equipment. In 1970, the species was listed as threatened under the Endangered Species Act. When scientists learned that commercial shrimp trawling nets were trapping and killing between 5000 and 50,000 loggerhead sea turtles a year, they developed a large metal grid called a Turtle Excluder Device (TED) that fits into the trawl net, preventing 97 percent of trawl-related loggerhead turtle deaths while only minimally