Where is the Planet heading To? Everyday we hear an ever increasing number of stories relating to ecological devastation, environmental destruction at a vast unimaginable scale, mass pollution and extinction of species have become daily songs in the mainstream media, not to mention the ever increasing effects of climate change and Global warming. could this planet be doomed already, is there really any hope for our world?
Never in history has our planet faced environmental challenges of such a grave magnitude. Everywhere we turn, we see death and destruction.
Experts continue to warn us that if humanity continues with their current uncontrollable behavior, planet earth will no longer be habitable in the coming few decades, it is ironic that humans are striving very had to create technology that will enable them to mars while they don’t find technology to help us solve our planet’ problems. We should try very hard to solve the problems we already have on our planet earth instead of wasting resources trying to reach a far distant planet that is completely inhabitable. The very fact that our planet earth is the only habitable celestial body in the whole universe speaks volumes for itself, it reminds us that we should strive to conserve and protect the little we already have instead of travelling into space to look to life elsewhere in places it can never exist at all. We need to start by reducing greenhouse gases emissions and other forms of pollution.
Our world is one ecological continent, one highly interactive biosphere, and damage done to any one ecosystem can have ill effects on many others. Burning high-sulfur coal in Illinois kills trees in Vermont, while dumping refrigerator coolants in New York destroys atmospheric ozone over Antarctica and leads to increased skin cancer in Madrid. Biologists call such widespread effects on the worldwide ecosystem global change. The pattern of global change that has become evident within recent years, including chemical pollution, acid precipitation, the ozone hole, the greenhouse effect, and the loss of biodiversity, is one of the most serious problems facing humanity’s future.
The problem posed by chemical pollution has grown very serious in recent years, both because of the growth of heavy industry and because of an overly casual attitude in industrialized countries. In one example, a poorly piloted oil tanker named the Exxon Valdez ran aground in Alaska in 1989 and heavily polluted with oil many kilometers of North American coastline, and the organisms that live there. If the tanker had been loaded no higher than the waterline, little oil would have been lost, but it was loaded far higher than that, and the weight of the above-waterline oil forced thousands of tons of oil out the hole in the ship’s hull. Why do policies permit overloading like this?
Chemicals are released into both the air and into water; therefore, their effects are far reaching.
Air Pollution. Air pollution is a major problem in the world’s cities. In Mexico City, oxygen is sold routinely on corners for patrons to inhale. Cities such as New York, Boston, and Philadelphia are known as gray-air cities because the pollutants in the air are usually sulfur oxides emitted by industry. Cities such as Los Angeles, however, are called brown-air cities because the pollutants in the air undergo chemical reactions in the sunlight to form smog.
Water Pollution. Water pollution is a very serious consequence of our casual attitude about pollution. “Flushing it down the sink” doesn’t work in today’s crowded world. There is simply not enough water available to dilute the many substances that the enormous human population produces continuously. Despite improved methods of sewage treatment, lakes and rivers throughout the world are becoming increasingly polluted with sewage. In addition, fertilizers and insecticides also get washed from the land to the water in great quantities.
The spread of “modern” agriculture, and particularly the Green Revolution, which brought high-intensity farming to developing countries, has caused very large amounts of many kinds of new chemicals to be introduced into the global ecosystem, particularly pesticides, herbicides, and fertilizers. Industrialized countries like the United States now attempt to carefully monitor side effects of these chemicals. Unfortunately, large quantities of many toxic chemicals, although no longer manufactured, still circulate in the ecosystem.
For example, the chlorinated hydrocarbons, a class of compounds that includes DDT, chlordane, lindane, and dieldrin, have all been banned for normal use in the United States, where they were once widely used. They are still manufactured in the United States and exported to other countries, where their use continues. Chlorinated hydrocarbon molecules break down slowly and accumulate in animal fat tissue. Furthermore, as they pass through a food chain, they become increasingly concentrated in a process called biological magnification.
shows how a minute concentration of DDT in plankton increases to significant levels as it is passed up through this aquatic food chain. DDT caused serious ecological problems by leading to the production of thin, fragile eggshells in many predatory bird species, such as peregrine falcons, bald eagles, osprey, and brown pelicans, in the United States and elsewhere until the late 1960s, when it was banned in time to save the birds from extinction. Chlorinated compounds have other undesirable side effects and exhibit hormonelike activities in the bodies of animals.
The Comers smokestacks power you see are those of the Four tall sending fur stacks. the smoke plant smoke high in New contains into Mexico. the high atmosphere This concentrations facility through burns of these coal, sul-combine introduced having spread high dioxide in through tall the with in and smokestacks atmosphere, Britain water other Europe vapor in sulfates, the and where was in mid-1950s, the to which winds release United air. The produce would and the States. first the sulfur-rich disperse tall acid design The stacks when intent rapidly and smoke were they di-oflute it, carrying the acids faraway.
However, in the 1970s, scientists began noticing that the acids from the sulfur-rich smoke were having devastating effects. Throughout northern Europe, lakes were reported to have suffered drastic drops in biodiversity, some even becoming devoid of life. The trees of the great Black Forest of Germany seemed to be dying-and the damage was not limited to Europe. In the eastern United States and Canada, many of the forests and lakes in the eastern United States and Canada have been seriously damaged.
It turns out that when the sulfur introduced into the upper atmosphere combined with water vapor to produce sulfuric acid, the acid was taken far from its source, but it later fell along with water as acidic rain and snow. This pollution-acidified precipitation is called acid rain (but the term acid precipitation is actually more correct).
Natural rainwater rarely has a pH lower than 5.6; however, rain and less snow than in 5.3, many and areas in the of the northeastern United States U.S., have pHs, pH of values have been recorded, with occasional storms as 4.2 or below
low as 3.0. precipitation United destroys States and life. Many of the been forests seri-of Acid the north eastern In fact, it is now estimated Canada that have at least 1.4ouslydamaged.
million acres of forests in the Northern Hemisphere have been adversely affected by acid precipitation. In addition, thousands of lakes in Sweden and Norway no longer support fish-these lakes are now eerily clear. In the northeastern United States and Canada, tens of thousands of lakes are dying biologically as their pH levels fall to below 5.0. At pH levels below 5.0, many fish species and other aquatic animals die, unable to reproduce.
The solution seems like it would be easy-clean up the sulfur emissions. But there have been serious problems with implementing this solution. First, it is expensive. Estimates of the cost of installing and maintaining the necessary “scrubbers” in the United States are on the order of $5 billion a year. An additional difficulty is that the polluter and the recipient of the pollution are far from one another, and neither wants to pay so much for what they view as someone else’s problem. The Clean Air Act revisions of 1990 have begun to address this problem by mandating some cleaning of emissions in the United States, although much still remains to be done worldwide.
The Ozone Hole
For 2 billion years, life was trapped in the oceans because radiation from the sun seared the earth’s surface unchecked. Nothing could survive that bath of destructive energy. Living things were able to leave the oceans and colonize the surface of the earth only after a protective shield of ozone had been added to the atmosphere by photosynthesis. Imagine if that shield were taken away. Alarmingly, it appears that we are destroying it ourselves. Starting in 1975, the earth’s ozone shield began to disintegrate. Over the South Pole in September of that year, satellite photos revealed that the ozone concentration was unexpectedly less than elsewhere in the earth’s atmosphere. It was as if some “ozone eater” were chewing it up in the Antarctic sky, leaving a mysterious zone of lower than-normal ozone concentration, an ozone hole. Every year after that, more of the ozone has been depleted, and the hole grows bigger and deeper. The satellite image shows lower levels of ozone as light purple (Antarctica is also colored purple, indicating that the ozone hole completely covers it). The graph indicates the size of the ozone hole over a 10-year period, with the largest hole appearing in September of 2000 (the blue line).
What is eating the ozone? Scientists soon discovered that the culprit was a class of chemicals that everyone had thought to be harmless: chlorofluorocarbons (CFCs). CFCs were invented in the 1920s, a miracle chemical that was stable, harmless, and a near-ideal heat exchanger. Throughout the world, CFCs are used in large amounts as coolants in refrigerators and air conditioners, as the gas in aerosol dispensers, and as the foaming agent in Styrofoam containers. All of these CFCs eventually escape into the atmosphere, but no one worried about this until recently, both because CFCs were thought to be chemically inert and because everyone tends to think of the atmosphere as limitless. But CFCs are very stable chemicals, and have continually accumulated in the atmosphere.
It turned out that the CFCs were causing mischief the chemists had not imagined. High over the South and North Poles, nearly 50 kilometers up, where it was very, very cold. the CFCs stuck to frozen water vapor and began to act as catalysts of a chemical reaction. Just as an enzyme carries out a reaction in your cells without being changed itself, so the CFCs began to catalyze the conversion of ozone (03) into oxygen (O2) without being used up themselves. Very stable, the CFCs in the atmosphere just kept at it-little machines that never stop. They are still there, still doing it, today. The drop in ozone worldwide is now over 3%.
Ultraviolet radiation is a serious human health concern. Every 1% drop in the atmospheric ozone content is estimated to lead to a 6% increase in the incidence of skin cancers. At middle latitudes, the drop of approximately 3% that has occurred worldwide is estimated to have led to an increase of perhaps as much as 20% in lethal melanoma skin cancers.
Experts generally agree that levels of ozone-killing chemicals in the upper atmosphere are leveling off since more than 180 countries in the 1980s signed an international agreement, which phases out the manufacture of most CFCs. The 2005 ozone hole peaked at about 25 million square kilometers (the size of North America), below the 2000 record size of about 28.4 million square kilometers. Current computer models suggest the Antarctic ozone hole should recover by 2065, and the lesser-damaged ozone layer over the Arctic by about 2023.
40.3 CFCs and other chemicals are catalytically destroying the ozone in the upper atmosphere, exposing the earth’s surface to dangerous radiation. International attempts to solve the problem appear to be succeeding.
The ozone hole over Antarctica.
For decades NASA satellites have tracked the extent of ozone depletion over Antarctica. Every year since 1975 an ozone “hole” has appeared in August when sunlight triggers chemical reactions in cold air trapped over the South Pole during Antarctic winter. The hole intensifies during September before tailing off as temperatures rise in November-December. In 2000, the 28.4-million-square-kilometer hole (purple in the satellite image) covered an area larger than the United States, Canada, and Mexico combined, the largest hole ever recorded. In September 2000, the hole extended over Punta Arenas, a city of about 120,000 people in southern Chile, exposing residents to very high levels of UV radiation.
For over 150 years, the growth of our industrial society has been fueled by cheap energy, much of it obtained by burning fossil fuels-coal, oil, and gas. Coal, oil, and gas are the remains of ancient plants, transformed by pressure and time into carbon-rich “fossil fuels.” When such fossil fuels are burned, this carbon is combined with oxygen atoms, producing carbon dioxide (CO2). Industrial society’s burning of fossil fuels has released huge amounts of carbon dioxide into the atmosphere. As with CFCs, no one paid any attention to this because the carbon dioxide was thought to be harmless and because the atmosphere was thought to be a limitless reservoir, able to absorb and disperse any amount. It turns out neither assumption was true, and in recent decades, the levels of carbon dioxide in the atmosphere have risen sharply and continue to rise.
What is alarming is that the carbon dioxide doesn’t just sit in the air doing nothing. The chemical bonds in carbon dioxide molecules transmit radiant energy from the sun but trap the longer wavelengths of infrared light, or heat, and prevent them from radiating into space. This creates what is known as the greenhouse effect. Planets that lack this type of “trapping” atmosphere are much colder than those that possess one. If the earth did not have a “trapping” atmosphere, the average earth temperature would be about -20?C, instead of the actual +15?C.
The earth’s greenhouse effect is intensifying with increased fossil fuel combustion and certain types of waste disposal. These activities are increasing the amounts of carbon dioxide, CFCs, nitrogen oxides, and methane-all “greenhouse gases”-in the atmosphere. The rise in average global temperatures during recent decades (shown as the red line. is consistent with increased carbon dioxide concentrations in the atmosphere (the blue line). The idea of global warming due to accumulation of greenhouse gases in the earth’s atmosphere has been controversial, because correlations do not prove a cause-and-effect relationship. However, as more data become available, a growing consensus of scientists accept global warming as an unwelcome reality.
Increases in the amounts of greenhouse gases could increase average global temperatures from 1? to 4? C, which could have serious impact on rain patterns in prime agricultural lands, and in changes in sea levels.
Effects on Rain Patterns.
Global warming is predicted to have a major effect on rainfall patterns. Areas that have already been experiencing droughts may see even less rain, contributing to even greater water shortages. Recent increases in the frequency of El Ni?o events (see chapter 37) and catastrophic hurricanes may indicate that global warming climatic changes are already beginning to occur.
Effects on Agriculture.
Both positive and negative effects of global warming on agriculture are predicted. Warmer tem-
The greenhouse effect.
The concentration of carbon dioxide in the atmosphere has shown a steady increase for many years (blue line). The red line shows the average global temperature for the same period of time. Note the general increase in temperature since the 1950s and, specifically, the sharp rise beginning in the 1980s. Data from Geophysical Monograph, American Geophysical Union, National Academy of Sciences, and National Center for Atmospheric Research.
temperatures and increased levels of carbon dioxide in the atmosphere would be expected to increase the yields of some crops, while having a negative impact on others. Droughts that may result from global warming will also negatively affect crops. Plants in the tropics are growing at maximal temperature limits; any further increases in temperature will probably begin to have a negative impact on agricultural yields of tropical farms.
Rising Sea Levels.
Much of the water on earth is locked into ice in glaciers and polar ice caps. As global temperatures increase, these large stores of ice have begun to melt. Most of the water from the melted ice ends up in the oceans, causing water levels to rise (but because the Arctic ice cap floats, its melting will not raise sea levels, any more than melting ice raises the level of water in a glass). Higher water levels can be expected to cause increased flooding of low-lying lands.
There is considerable disagreement among governments about what ought to be done about global warming. The Clean Air Act of 1990 and the Kyoto Treaty have established goals for reducing the emission of greenhouse gases. Countries across the globe are making progress toward reducing emissions, but much more needs to be done.
Humanity’s burning of fossil fuels has greatly increased atmospheric levels of CO2, leading to global warming.
Loss of Biodiversity
Just as death is as necessary to a normal life cycle as reproduction, so extinction is as normal and necessary to a stable world ecosystem as species formation. Most species, probably all, go extinct eventually. More than 99% of species known to science (most from the fossil record) are now extinct. However, current rates of extinctions are alarmingly high. The extinction rate for birds and mammals was about one species every decade from 1600 to 1700, but it rose to one species every year during the period from 1850 to 1950, and four species per year between 1986 and 1990. It is this increase in the rate of extinction that is the heart of the biodiversity crisis.
Factors Responsible for Extinction
What factors are responsible for extinction? Studying a wide array of recorded extinctions, and many species currently threatened with extinction, biologists have identified three factors that seem to play a key role in many extinctions: habitat loss, species overexploitation, and introduced species. Habitat Loss. Habitat loss is the single most important cause of extinction. Given the tremendous amounts of ongoing destruction of all types of habitat, from rain forest to ocean floor, this should come as no surprise. Natural habitats may be adversely affected by human influences in four ways: (1) destruction, (2) pollution, (3) human disruption, and (4) habitat fragmentation (dividing up the habitat into small isolated areas). Habitat destruction is rapidly endangering species on Madagascar. You can see the loss of rain forest habitat, colored in green on the overlain maps
Extinction and habitat destruction.
The rain forest covering the eastern coast of Madagascar, an island off the coast of East Africa, has been progressively destroyed as the island’s human population has grown. Ninety percent of the original forest cover is now gone. Many species have become extinct, and many others are threatened, including 16 of Madagascar’s 31 primate species.
Species that are hunted or harvested by humans have historically been at grave risk of extinction, even when the species populations are initially very abundant. There are many examples in our recent history of overexploitation: passenger pigeons, bison, many species of whales, commercial fish such as Atlantic bluefin tuna, and mahogany trees in the West Indies are but a few.
Occasionally, a new species will enter a habitat and colonize it, usually at the expense of native species. Colonization occurs in nature, but it is rare; however, humans have made this process more common with devastating ecological consequence. The introduction of exotic species has wiped out or threatened many native populations. African bees (page 749) are an obvious example. Species introductions occur in many ways, usually unintentionally. Plants and animals can be transported in nursery plants, in the ballast of large ocean vessels, as stowaways in boats, cars, and planes, and as beetle larvae within wood products. These species enter new environments where they have no native predators to keep their population sizes in check. Free to populate the habitat, they crowd out native species.
The loss of biodiversity can usually be attributed to one of a few main causes, including habitat loss, overexploitation, and introduced species.
The Global Decline in Amphibians
Sometimes important things happen, right under our eyes, without anyone noticing. That thought occurred to David Bradford as he stood looking at a quiet lake high in the Sierra Nevada Mountains of California in the summer of 1988. Bradford, a biologist, had hiked all day to get to the lake, and when he got there his worst fears were confirmed. The lake was on a list of mountain lakes that Bradford had been visiting that summer in Sequoia-Kings Canyon National Parks while looking for a little frog with yellow legs. The frog’s scientific name was Rana muscosa, and it had lived in the lakes of the parks for as long as anyone had kept records. But this silent summer evening, the little frog was gone. The last major census of the frog’s populations within the parks had been taken in the mid1970s, and R. muscosa had been everywhere, a common inhabitant of the many freshwater ponds and lakes within the parks. Now, for some reason Bradford did not understand, the frogs had disappeared from 98% of the ponds that had been their homes.
After Bradford reported this puzzling disappearance to other biologists, an alarming pattern soon became evident. Throughout the world, local populations of amphibians (frogs, toads, and salamanders) were becoming extinct. Waves of extinction have swept through high-elevation amphibian populations in the western United States, and have also cut through the frogs of Central America and coastal Australia.
Amphibians have been around for 350 million years, since long before the dinosaurs. Their sudden disappearance from so many of their natural homes sounded an alarm among biologists. What are we doing to our world? If amphibians cannot survive the world we are making, can we?
In 1998 the U.S. National Research Council brought scientists together from many disciplines in a serious attempt to address the problem. After years of intensive investigation, they have begun to sort out the reasons for the global decline in amphibians. Like many important questions in science, this one does not have a simple answer.
Four factors seem to be contributing in a major way to the worldwide amphibian decline: (1) deterioration and destruction, particularly of forests, which drastically lowers the humidity in the air) that amphibians require; (2) the introduction
of exotic species that outcompete local amphibian populations; amphibians; Infection (3) and by chemical parasites (4) fatal appears pollutants infections to have by that pathogens are played toxic atoms
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Collins the Kaibab examined Plateau populations along the Grand of salamanders Canyon rim, living he on found many sick salamanders. Their skin was covered with white pustules, and most infected ones died, their hearts and spleens collapsed. The infectious agent proved to be a virus common in fish called a ranavirus. Ranavirus isolated by Collins from one sick salamander would cause the disease in a healthy salamander, so there was no doubt that ranavirus was the culprit responsible for the salamander decline on the Kaibab Plateau.
Ranavirus outbreaks eliminate small populations, but in larger ones a few individuals survive infection, sloughing off their pustule-laden skin. These populations slowly recover.
A second kind of infection, very common in Australia but also seen in the United States, is the real species killer.
Populations infected with this microbe, a kind of fungus called a chytrid (pronounced “kit-rid,” see chapter 21), do not recover. Usually, a harmless soil fungus that decomposes plant material, this particular chytrid (with the Latin name of Batrachochytrium dendrobatidis) is far from harmless to amphibians. It dissolves and absorbs the chitinous mouthparts of amphibian larvae, killing them.
This killer chytrid was introduced to Australia near Melbourne in the early 1980s. Now almost all Australia is affected. How did the disease spread so rapidly? Apparently, it traveled by truck. Infected frogs moved all across Australia in wooden boxes with bunches of bananas. In one year, 5,000 frogs were collected from banana crates in one Melbourne market alone.
In other parts of the world, infection does not seem to play as important a role as acid precipitation, habitat loss, and introduction of exotic species. This complex pattern of cause and effect only serves to emphasize the take-home lesson: worldwide amphibian decline has no one culprit. Instead, all four factors play important roles. It is their total impact that has shifted the worldwide balance toward extinction. Toward extinction, we must work to reverse the trend
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The pattern of global change that is overtaking our world is very disturbing. Human activities are placing a severe stress on the biosphere, and we must quickly find ways to reduce the harmful impact. There are four key areas in which it will be particularly important to meet the challenge successfully: reducing pollution, finding other sources of energy, preserving nonreplaceable resources, and curbing population growth.
To solve the problem of industrial pollution, it is first necessary to understand the cause of the problem. In essence, it is a failure of our economy to set a proper price on environmental health. To understand how this happens, we must think for a moment about money. The economy of the United States (and much of the rest of the industrial world) is based on a simple feedback system of supply and demand. As a commodity gets scarce, its price goes up, and this added profit acts as an incentive for more of the item to be produced; if too much is produced, the price falls and less of it is made because it is no longer so profitable to produce it.
This system works very well and is responsible for the economic strength of our nation, but it has one great weakness. If demand is set by price, then it is very important that all the costs be included in the price. Imagine that the person selling the item were able to pass off part of the production cost to a third person. The seller would then be able to set a lower price and sell more of the item! Driven by the lower price, the buyer would purchase more than if all the costs had been added into the price.
Unfortunately, that sort of pricing error is what has driven the pollution of the environment by industry. The true costs of energy and of the many products of industry are composed of direct production costs, such as materials and wages, and of indirect costs, such as pollution of the ecosystem. Economists have identified an “optimum” amount of pollution based on how much it costs to reduce pollution versus the social and environmental cost of allowing pollution. The economically optimum amount of pollution is indicated by the blue dot. If more pollution than the optimum is allowed, the social cost is too high, but if less than the optimum is allowed, the economic cost is too high.
The indirect costs of pollution are usually not taken into account. However, the indirect costs do not disappear because we ignore them. They are simply passed on to future generations, which must pay the bill in terms of damage to the ecosystems on which we all depend. Increasingly, the future is now. Our world, unable to support more damage, is demanding that something be done-that we finally pay up.
Two effective approaches have been devised to curb pollution in this country. The first is to pass laws forbidding it. In the last 20 years, laws have begun to significantly curb
Is there an optimum amount of pollution?
Economists identify the “optimum” amount of pollution as the practice at which eliminating the next unit of pollution (the marginal cost of pollution abatement) equals the cost in damages caused by the unit of pollution (the marginal cost of pollution).
the spread of pollution by setting stiff standards for what can be released into the environment. For example, all cars are required to have effective catalytic converters to eliminate automobile smog. Similarly, the Clean Air Act of 1990 requires that power plants eliminate sulfur emissions. They can accomplish this by either installing scrubbers on their smoke stacks or by burning low-sulfur coal (clean-coal technology), which is more expensive. The effect is that the consumer pays to avoid polluting the environment. The cost of the converters makes cars more expensive, and the cost of the scrubbers increases the price of the energy. The new, higher costs are closer to the true costs, lowering consumption to more appropriate levels.
A second approach to curbing pollution has been to increase the consumer costs directly by placing a tax on the pollution, in effect an artificial price hike imposed by the government as a tax added to the price of production. This added cost lowers consumption too, but by adjusting the tax, the government can attempt to balance the conflicting demands of environmental safety and economic growth. Such taxes, often imposed as “pollution permits,” are becoming an increasingly important part of antipollution laws.
Free market economies often foster pollution when prices do not include environmental costs. Laws and taxes are being designed in an attempt to compensate.
Finding Other Sources of Energy
The pollution generated by burning coal and oil, the increasing scarcity of oil, and the potential contributions of carbon dioxide to global warming all make it desirable to find alternative energy sources. Many countries are turning to nuclear power for their growing energy needs. In less than 50 years, nuclear power has become a leading source of energy. In 1995, more than 500 nuclear reactors were producing power worldwide. Over 70% of France’s electricity is now produced by nuclear power plants.
Nuclear power plants have not been as popular in this country as in the rest of the world, because we have ample access to cheap coal and because the public fears the consequences of an accident. A reactor partial meltdown at the Three Mile Island nuclear plant in Pennsylvania in 1979 released little radiation into the environment but galvanized these fears. There has been little nuclear power development in this country since then
In theory, nuclear power can provide plentiful, cheap energy, but the reality is less encouraging. Nuclear power presents several problems-safety, waste disposal, security- that must be overcome if it is to provide a significant portion of the energy that will fuel our future world.
Alternative Energy Sources
A variety of other sources of energy can help reduce our use of fossil fuels, chief among these is solar power. A variety of technologies has been developed that are increasingly effective.
Alternate energy sources.
(a) Solar energy uses large mirrors to collect energy from the sun.
These solar panels absorb heat from the sun that is used to boil water
(or other fluids), which creates steam. The steam turns large turbines (not pictured), generating electricity. (b) Wind-powered energy is an old technology modernized for large-scale use. Large wind fields harness the kinetic energy in wind, converting it into electricity.
efficient at capturing the energy in the sun’s rays. The large solar panels capture this energy to heat water or other fluids to make steam that turns a turbine, generating electricity. Smaller applications use solar panels connected to photovoltaic cells, which convert solar energy directly into electricity.
Other sources of energy include capturing the energy in the wind, accomplished by wind farms like the one shown, and tapping the earth’s heat in places, such as near hot springs, where it rises to the earth’s surface. In the longer run, nuclear fusion reactors and automobiles running on hydrogen gas may provide great amounts of energy at lower cost with little pollution. Currently, these sources of energy contribute relatively little to our energy budget. However, as technologies improve and the cost of fossil fuels rises, these sources will become increasingly important.
Safety, security, and particularly waste disposal remain serious obstacles to the widespread use of nuclear power. Alternate sources of energy are becoming increasingly important.
Preserving Nonreplaceable Resources
Among the many ways ecosystems are being damaged, one class of problem stands out as more serious than all the rest: consuming or destroying resources that we all share in common but cannot replace in the future. Although a polluted stream can be cleaned, no one can restore an extinct species. In the United States, three sorts of nonreplaceable resources are being reduced at alarming rates: topsoil, groundwater, and biodiversity.
Soil is composed of a mixture of rocks and minerals with partially decayed organic matter called humus. Plant growth is strongly affected by soil composition. Minerals like nitrogen and phosphorus are critical to plant growth, and are abundant in humus-rich soils.
The United States is one of the most productive agricultural countries on earth, largely because much of it is covered with particularly fertile soils. Our midwestern farm belt sits astride what was once a great prairie. The soil of that ecosystem accumulated bit by bit from countless generations of animals and plants until, by the time humans came to plow, the humus-rich soil extended down several feet.
“Freedom in a Commons Brings Ruin to All”
The essence of Hardin’s original essay:
Picture a pasture open to all. It is expected that each herdsman will try to keep as many cattle as possible on [this] commons …. What is the utility … of adding one more animal? … Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility [to the herdsman] is nearly +1 …. Since, however, the effects of overgrazing are shared by all the herdsmen, the negative utility for any particular decision-making herdsman is only a fraction of -1. Adding together the … partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to [the] herd. And another; and another …. Therein is the tragedy. Each man is locked into a system that [causes] him to increase his herd without limit-in a world that is limited …. Freedom in a commons brings ruin to all.
We cannot replace this rich topsoil, the capital upon which our country’s greatness is built, yet we are allowing it to be lost at a rate of centimeters every decade. Our country has lost one quarter of its topsoil since 1950! By repeatedly tilling (turning the soil over) to eliminate weeds, we permit rain to wash more and more of the topsoil away, into rivers and eventually out to sea. New approaches are desperately needed to lessen the reliance on intensive cultivation. Some possible solutions include using genetic engineering to make crops resistant to weedkilling herbicides and terracing to recapture lost topsoil.
A second resource that we cannot replace is groundwater, water trapped beneath the soil within porous rock reservoirs called aquifers. This water seeped into its underground reservoir very slowly during the last ice age over 12,000 years ago. We should not waste this treasure, for we cannot replace it.
In most areas of the United States, local governments exert relatively little control over the use of groundwater. As a result, a very large portion is wasted watering lawns, washing cars, and running fountains. A great deal more is inadvertently being polluted by poor disposal of chemical wastes-and once pollution enters the groundwater, there is no effective means of removing it. Some cities, like Phoenix and Las Vegas, may completely deplete their groundwater within several decades.
Tropical rain forest destruction.
(a) These fires are destroying the rain forest in Brazil, which is being cleared for cattle pasture. (b) The flames are so widespread and so high that their smoke can be viewed from space. (c) The consequences of deforestation can be seen on these middle-elevation slopes in Ecuador. The slopes now support only low-grade pastures where they used to support highly productive forest.
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20 ourselves. kinds of the plants, fact out that of our the entire 250,000 supply available, of food should is based give on us pause. Like burning a library without reading the books, we don’t know what it is we waste. All we can be sure of is that we cannot retrieve it. Extinct is forever.
Over the last 20 years, about half of the world’s tropical rain forests have been either burned to make pasture land or cut for timber. Over 6 million square kilometers have been destroyed. Every year the rate of loss increases as the human population of the tropics grows. About 160,000 square kilometers were cut each year in the 1990s, a rate greater than 0.6 hectares (1.5 acres) per second! At this rate, all the rain forests of the world will be gone in your lifetime. In the process, it is estimated that one-fifth or more of the world’s species of animals and plants will become extinct-more than a million species. This would be an extinction event unparalleled for at least 65 million years, since the Age of Dinosaurs.
You should not be lulled into thinking that loss of biodiversity is a problem limited to the tropics. The ancient forests of the Pacific Northwest are being cut at a ferocious rate today, largely to supply jobs (the lumber is exported), with much of the cost of cutting it down subsidized by our government (the Forest Service builds the necessary access roads, for example). At the current rate, very little will remain in a decade. Nor is the problem restricted to one area. Throughout our country, natural forests are being “clear-cut,” replaced by pure stands of lumber trees planted in rows like so many lines of corn. It is difficult to scold those living in the tropics when we ourselves do such a poor job of preserving our own country’s biodiversity.
But what is so bad about losing species? What is the value of biodiversity? Loss of a species entails three costs: the direct economic value of the products we might have obtained from species; by species without the indirect our economic consuming value them, of ben-such benefits as nutrient produced recycling in ecosystems; and their ethical and aesthetic value. It is to not obtain difficult food, to medicine, see the value clothing, in protecting energy, species that we use species are vitally important to maintain and shelter, but other by destroying biodiversity, we are training healthy ecosystems; lessened productivity. creating Other species conditions add beauty of instability to the living and world, no less crucial because it is hard to set a price upon.
Nonreplaceable at an alarming topsoil, resources groundwater, are over being the and world,
rate all key among them biodiversity.
Curbing Population Growth
If we were to solve all the problems mentioned in this chapter, we would merely buy time to address the fundamental problem: there are getting to be too many of us.
Humans first reached North America at least 12,000 to 13,000 years ago, crossing the narrow straits between Siberia and Alaska and moving swiftly to the southern tip of South America. By 10,000 years ago, when the continental ice sheets withdrew and agriculture first developed, about 5 million people lived on earth, distributed over all the continents except Antarctica. With the new and much more dependable sources of food that became available through agriculture, the human population began to grow more rapidly. By the time of Christ, 2,000 years ago, an estimated 130 million people lived on earth. By the year 1650, the world’s population had doubled, and doubled again, reaching 500 million. Starting in the early 1700s, changes in technology have given humans more control over their food supply, enabled them to develop superior weapons to ward off predators, and led to the development of cures for many diseases. At the same time, improvements in shelter and storage capabilities have made humans less vulnerable to climatic uncertainties. Recall from chapter 38, that populations grow exponentially until they reach the limits of their environment, called the carrying capacity. These changes since the 1700s allowed humans to expand the carrying capacity of the habitats in which they lived and thus to escape the confines of logistic growth and reenter the exponential phase of the sigmoidal growth curve, shown by the explosive growth.
Although the human population has grown explosively for the last 300 years, the average human birthrate has stabilized at about 21 births per year per 1,000 people worldwide. However, with the spread of better sanitation and improved medical techniques, the death rate has fallen steadily, to its present level of 9 per 1,000 per year. The difference between birth and death rates amounts to a population growth rate of 1.2% per year, which seems like a small number, but it is not, given the large population size.
The world population reached 6.5 billion people in 2004, and the annual increase now amounts to about 78 million people, which leads to a doubling of the world population in about 58 years. Put another way, more than 214,000 people are added to the world population each day, or almost 150 every minute. At this rate, the world’s population will continue to grow and perhaps stabilize at a figure between 7.3 billion and 10.7 billion. Such growth cannot continue, because our world cannot support it. Just as a cancer cannot grow unabated in your body without eventually killing you, so humanity cannot continue to grow unchecked in the biosphere without killing it.
One of the most alarming trends taking place in developing countries is the massive movement to urban centers. For example, Mexico City, one of the largest cities in the world, is plagued by smog, traffic, inadequate waste disposal, and other problems; it has a population of about 26 million people
Growth curve of the human population.
Over the past 300 years, the world population has been growing steadily. Currently, there are over 6 billion people on the earth.
The prospects of supplying adequate food, water, and sanitation to this city’s people are almost unimaginable. The lot of the rural poor, mainly farmers, in Mexico is even worse.
In view of the limited resources available to the human population, and the need to learn how to manage those resources well, the first and most necessary step toward global prosperity is to stabilize the human population. One of the surest signs of the pressure being placed on the environment is human use of about 40% of the total net global photosynthetic productivity on land. Given that statistic, a doubling of the human population in 58 years poses extraordinarily severe problems. The facts virtually demand restraint in population growth. If and when technology is developed that would allow greater numbers of people to inhabit the earth in a stable condition, the human population can be increased to whatever level might be appropriate.
A key element in the world’s population growth is its uneven distribution among countries. gives a general breakdown of the distribution of the human population across the globe. At the beginning of the last century, the population was fairly evenly distributed between the developing countries (peach-colored area) and developed countries (red area). Of the billion people added to the world’s population in the 1990s, 80% to 90% live in developing countries and of that number, about 60% of the people in the world live in countries that are at least partly tropical or subtropical. An additional 20% live in China. The remaining 20% live in the so-called developed, or industrialized, countries: Europe, Russia, Japan, the United States, Canada, Australia, and New Zealand. Whereas the populations of the developed countries are growing at an annual rate of only about 0.1%, those of the less developed, mostly tropical countries (excluding China) are growing at an annual rate estimated to be about 1.9%.
Most countries are devoting considerable attention to slowing the growth rate of their populations, and there are genuine signs of progress but the world population may still gain another 1 to 4 billion people before it stabilizes. No one knows whether the world can support so many people indefinitely. Finding a way to do so is the greatest task facing humanity. The quality of life that will be available for your children in this new century will depend to a large extent on our success.
Population Growth Rate Has Been Declining
The world population growth rate has been declining, from a high of 2.0% in the period 1965-70 to 1.2% in 2004. Nonetheless, because of the larger population, this amounts to an increase of 78 million people per year to the world population, compared to 53 million per year in the 1960s.
The United Nations attributes the decline to increased family planning efforts and the increased economic power and social status of women. Although the United Nations applauds the United States for leading the world in funding family planning programs abroad, some oppose spending money on international family planning. The opposition states that money is better spent on improving education and the economy in other countries, leading to an increased awareness and lowered fertility rates. The United Nations certainly supports the improvement of education programs in developing countries, but, interestingly, it has reported increased education levels following a decrease in family size as a result of family planning.
Slowing population growth will help sustain the world’s resources, but per capita consumption is also important. Surprisingly, the majority of resource consumption occurs in developed countries, even though the majority of the world’s population is in developing countries. It is necessary that those in the developed world do a better job of lessening the impact each of us makes.
No one knows whether the world can sustain today’s population of over 6.5 billion people, much less the far greater numbers expected in the future. We cannot reasonably expect to expand the world’s carrying capacity indefinitely. The population will begin scaling back in size, as predicted by logistic
growth models; indeed, it is already happening. In the sub-Saharan area of Africa, population projections for the year 2025 have been scaled back from 1.33 billion to 1.05 billion because of the impact of AIDS. If we are to avoid catastrophic increases in death rates, such as the tragedy we are seeing in the sub-Saharan, the birthrates must continue to fall dramatically.
Distribution of population growth.
Most of the worldwide increase in population since 1950 has occurred in developing countries. This trend will likely increase in the near future. World population in 2050 is estimated to be around 9 billion, according to recent projections. Depending on fertility rates, the population at that time will either be increasing rapidly or slightly, or in the best case, declining slightly.
While the human population as a whole continues to grow rapidly, this growth is not occurring uniformly over the planet. Some countries, like Mexico, are currently growing rapidly. shows how Mexico’s birthrate, while declining (the blue line), still greatly exceeds its death rate (the red line), which is also declining. There is often a correlation in how developed a country is and how rapidly its population grows. Table 40.1 compares three countries that differ in how well developed they are. Ethiopia, a developing country, has a higher fertility rate, which results in a higher birthrate than either Brazil or the United States but it also has a much higher infant mortality rate and a lower life expectancy. But overall, it will double its population much more quickly than Brazil or the United States. The rate at which a population can be expected to grow in the future can be assessed graphically by means of a population pyramid-a bar graph displaying the numbers of people in each age category (some examples are shown. Males are conventionally shown to the left of the vertical age axis (colored blue here) and females to the right (colored red). In most human population pyramids, the number of older females is disproportionately large compared with the number of older males, because females in most regions have a longer life expectancy than males. This is apparent in the upper portion of the 2005 U.S. pyramid.
Viewing such a pyramid, one can predict demographic trends in births and deaths. In general, rectangular pyramids are characteristic of countries whose populations are stable; their numbers are neither growing nor shrinking. A triangular pyramid, like the 2005 Kenya pyramid, is characteristic of a country that will exhibit rapid future growth, as most of its population has not yet entered the child-bearing years. Inverted triangles are characteristic of populations that are shrinking.
Compare the differences in the population pyramids for the United States and Kenya in. In the somewhat more rectangular population pyramid for the United States in 2005, the cohort (group of individuals) 40 to 59 years old represents the “baby boom,” the large number of babies born following World War II. When the media refers to the “graying of America,” they are referring to the aging of this disproportionately large cohort that will impact the health-care system and other age-related systems in the future. The very triangular pyramid of Kenya, by contrast, predicts explosive future growth. The population of Kenya is predicted to double in less than 20 years. However, it is important to note that these estimates do not take into account the huge impact that natural disasters such as the AIDS epidemic will have on population sizes. In sub-Sahara Africa, the AIDS epidemic has reduced the life expectancy at birth by 20 years. shows two population pyramid projections for Botswana, Africa, where over 36% of the population is living with HIV or AIDS. The uncolored portions of the bars indicate what the population would be like in 2025 without the effect of the AIDS epidemic, and the colored bars reflect actual projections.
The Level of Consumption in the Developed World Is Also a Problem
The world population is expected to stabilize sometime in this century at about 10 billion. We in the developed countries of the world need to pay more attention to lessening the impact of our resource consumption. Indeed, the wealthiest 20% of the world’s population accounts for 86% of the world’s consumption of resources and produces 53% of the world’s carbon dioxide emissions, whereas the poorest 20% of the world is responsible for only 1.3% of consumption and 3% of CO2 emissions.
Why Mexico’s population is growing.
The death rate (red line) in Mexico has been falling, while the birthrate (blue line) remained fairly steady until 1970. The difference between birth and death rates has fueled a high growth rate. Efforts begun in 1970 to reduce the birthrate have been quite successful. Although the growth rate remains rapid, it is expected to begin leveling off in the near future as the birthrate continues to drop.
Preserving Endangered Species
Once you understand the reasons why a particular species is endangered, it becomes possible to think of designing a recovery plan. If the cause is commercial overharvesting, regulations can be designed to lessen the impact and protect the threatened species. If the cause is habitat loss, plans can be instituted to restore lost habitat. Loss of genetic variability in isolated subpopulations can be countered by transplanting individuals from genetically different populations. Populations in immediate danger of extinction can be captured, introduced into a captive breeding program, and later reintroduced to other suitable habitats.
Of course, all of these solutions are extremely expensive. As Bruce Babbitt, Interior Secretary in the Clinton administration, noted, it is much more economical to prevent such “environmental train wrecks” from occurring than it is to clean them up afterward. Preserving ecosystems and monitoring species before they are threatened is the most effective means of protecting the environment and preventing extinctions.
Conservation biology typically concerns itself with preserving populations and species in danger of decline or extinction. Conservation, however, requires that there be something left to preserve, while in many situations, conservation is no longer an option. Species, and in some cases whole communities, have disappeared or have been irretrievably modified. The clear-cutting of the temperate forests of Washington State leaves little behind to conserve; nor does converting a piece of land into a wheat field or an asphalt parking lot. Redeeming these situations requires restoration rather than conservation.
Three quite different sorts of habitat restoration programs might be undertaken, depending very much on the cause of the habitat loss.
In situations where all species have been effectively removed, one might attempt to restore the plants and animals that are believed to be the natural inhabitants of the area, when such information is available. When abandoned farmland is to be restored to prairie, how do you know what to plant? Although it is in principle possible to reestablish each of the original species in their original proportions, rebuilding a community requires that you know the identity of all of the original inhabitants, and the ecologies of each of the species. We rarely ever have this much information, so no restoration is truly pristine.
Removing Introduced Species.
Sometimes the habitat of a species has been destroyed by a single introduced species. In such a case, habitat restoration involves removal of the introduced species. For example, Lake Victoria, Africa, was home to over 300 species of cichlid fishes, small perch-like fishes
The University of Wisconsin-Madison Arboretum has pioneered restoration ecology. (a) The restoration of the prairie was at an early stage in November, 1935. (b) The prairie as it looks today. This picture was taken at approximately the same location as the 1935 photograph.
that display incredible diversity. However, in 1954, the Nile perch, a commercial fish with a voracious appetite, was introduced into Lake Victoria. For decades, these perch did not seem to have a significant impact, and then something happened to cause the Nile perch to explode and spread rapidly through the lake, eating their way through the cichlids By 1986, over 70% of cichlid species had disappeared, including all open-water species.
So what happened to kick-start the mass extinction of the cichlids? The trigger seems to have been eutrophication. High inputs of nutrients from agricultural runoff and sewage from towns and villages led to algal blooms that severely depleted oxygen levels in deeper parts of the lake. This is thought to have led to an increase in cichlids that feed on algae, and a subsequent explosion of Nile perch numbers. The situation has been compounded by a second factor, the introduction into Lake Victoria of a floating water weed from South America, the water hyacinth Eichhornia crassipes. Extremely prolific under eutrophic conditions, thick mats of water hyacinth soon covered entire bays and inlets, choking off the coastal habitats of non-open-water cichlids.
Restoration of the once-diverse cichlid fishes to Lake Victoria will require more than breeding and restocking the endangered species. Eutrophication will have to be reversed, and the introduced water hyacinth and Nile perch populations brought under control or removed.
Cleanup and Rehabilitation.
Habitats seriously degraded by chemical pollution cannot be restored until the pollution is cleaned up. The successful restoration of the Nashua River in New England, discussed later in this chapter, is one example of how a concerted effort can succeed in restoring a heavily polluted habitat to a relatively pristine condition.
Recovery programs, particularly those focused on one or a few species, often must involve direct intervention in natural populations to avoid an immediate threat of extinction. Introducing wild-caught individuals into captive breeding programs is being used in an attempt to save the black-footed ferret and California condor populations in immediate danger of disappearing. Several other such captive propagation programs have had success.
Case History: The Peregrine Falcon.
U.S. populations of birds of prey such as the Peregrine falcon (Falco peregrinus) began an abrupt decline shortly after World War II. Of the approximately 350 breeding pairs east of the Mississippi River in 1942, all had disappeared by 1960. The culprit proved to be the chemical pesticide DDT and related organochlorine pesticides. Birds of prey are particularly vulnerable to DDT because they feed at the top of the food chain, where DDT becomes concentrated. DDT interferes with the deposition of calcium in the bird’s eggshells, causing most of the eggs to break before they hatch.
The use of DDT was banned by federal law in 1972, causing levels in the eastern United States to fall quickly. There were no peregrine falcons left in the eastern United States to reestablish a natural population, however. Falcons from other parts of the country were used to establish a captive breeding program at Cornell University in 1970, with the intent of reestablishing the peregrine falcon in the eastern United States by releasing offspring of these birds. By the end of 1986, over 850 birds had been released in 13 eastern states, producing an astonishingly strong recovery.
Sustaining Genetic Diversity
One of the chief obstacles to a successful species recovery program is that a species is generally in serious trouble by the time a recovery program is instituted. When populations become very small, much of their genetic diversity is lost. If a program is to have any
chance of success, every effort must be made to sustain as much genetic diversity as possible.
Case History: The Black Rhino.
All five species of rhinoceros are critically endangered. The three Asian species live in a forest habitat that is rapidly being destroyed, while the two African species are illegally killed for their horns. Fewer than 11,000 individuals of all five species survive today. The problem is intensified by the fact that many of the remaining animals live in very small, isolated populations. The 2,400 wild-living individuals of the black rhino, Diceros bicornis, live in approximately 75 small, widely separated groups consisting of six subspecies adapted to local conditions throughout the species’ range. All of these subspecies appear to have low genetic variability; in three of the subspecies, only a few dozen animals remain. Analysis of mitochondrial DNA suggests that in these populations most individuals are genetically very similar.
This lack of genetic variability represents one of the greatest challenges to the future of the species. Much of the range of the black rhino is still open and not yet subject to human encroachment. To have any significant chance of success, a species recovery program will have to find a way to sustain the genetic diversity that remains in this species. Heterozygosity could be best maintained by bringing all black rhinos together in a single breeding population, but this is not a practical possibility. A more feasible solution would be to move individuals between populations. Managing the black rhino populations for genetic diversity could prevent the loss of genetic variation, which might prove fatal to this species.
Placing black rhinos from a number of different locations together in a sanctuary to increase genetic diversity raises a potential problem: local subspecies may be adapted in different ways to their immediate habitats-what if these local adaptations are crucial to their survival? Homogenizing the black rhino populations by pooling their genes risks destroying such local adaptations, if they exist, perhaps at great cost to survival.
Preserving Keystone Species
Keystone species are species that exert a particularly strong influence on the structure and functioning of their ecosystem. Their removal can have disastrous consequences.
Case History: Flying Foxes. The severe decline of many species of pteropodid bats, or “flying foxes,” in the Old-World tropics is an example of how the loss of a keystone species can have dramatic effects on the other species living within an ecosystem, sometimes even leading to a cascade of further extinctions These bats have very close relationships with important plant species on the islands of the Pacific and Indian Oceans. The family Pteropodidae contains nearly 200 species, approximately a quarter of them in the genus Pteropus, and is widespread on the islands of the South Pacific, where they are the most important-and
Preserving keystone species.
The flying fox is a keystone species in many Old-World tropical islands. It pollinates: many of the plants, and is a key disperser of seeds. Its elimination by hunting and habitat loss is having a devastating effect on the ecosystems of many South Pacific islands.
often the only-pollinators and seed dispersers. A study in Samoa found that 80% to 100% of the seeds landing on the ground during the dry season were deposited by flying foxes. Many species are entirely dependent on these bats for pollination.
In Guam, where the two local species of flying fox have recently been driven extinct or nearly so, the impact on the ecosystem appears to be substantial. Many plant species are not fruiting, or are doing so only marginally, with fewer fruits than normal. Fruits are not being dispersed away from parent plants, so offspring shoots are being crowded out by the adults.
Flying foxes are being driven to extinction by human hunting. They are hunted for food, for sport, and by orchard farmers, who consider them pests. Flying foxes are particularly vulnerable because they live in large, easily seen groups of up to a million individuals. Because they move in regular and predictable patterns and can be easily tracked to their home roost, hunters can easily bag thousands at a time.
Species preservation programs aimed at preserving particular species of flying foxes are only just beginning. One particularly successful example is the program to save the Rodrigues fruit bat, Pteropus rodricensis, which occurs only on Rodrigues Island in the Indian Ocean near Madagascar. The population dropped from about 1,000 individuals in 1955 to fewer than 100 by 1974, the drop reflecting largely the loss of the fruit bat’s forest habitat to farming. Since 1974 the species has been legally protected, and the forest area of the island is being increased through a tree-planting program. Eleven captive breeding colonies have been established, and the bat population is now increasing rapidly. The combination of le-
gal protection, habitat restoration, and captive breeding has in this instance produced a very effective preservation program.
Conservation of Ecosystems
Habitat fragmentation is one of the most pervasive enemies of biodiversity conservation efforts. Some species simply require large patches of habitat to thrive, and conservation efforts that cannot provide suitable habitat of such a size are doomed to failure. As it has become clear that isolated patches of habitat lose species far more rapidly than large preserves do, conservation biologists have promoted the creation, particularly in the tropics, of so-called mega reserves, large areas of land containing a core of one or more undisturbed habitats.
In addition to this focus on maintaining large enough reserves, in recent years, conservation biologists also have recognized that the best way to preserve biodiversity is to focus on preserving intact ecosystems, rather than focusing on particular species. For this reason, attention in many cases is turning to identifying those ecosystems most in need of preservation and devising the means to protect not only the species within the ecosystem, but the functioning of the ecosystem itself.
must 40.10deal Recovery with habitat programs loss at and the fragmentation, species level and often with a marked reduction in genetic diversity. Captive breeding programs that stabilize genetic diversity and pay careful attention to habitat preservation and restoration are typically involved in successful recoveries.
Individuals Can Make the Difference
The development of appropriate solutions to the world’s environmental problems must rest partly on the shoulders of politicians, economists, bankers, engineers-many kinds of public and commercial activity will be required. However, it is important not to lose sight of the key role often played by informed individuals in solving environmental problems. Often one person has made the difference; two examples serve to illustrate the point.
The Nashua River
Running through the heart of New England, the Nashua River was severely polluted by mills established in Massachusetts in the early 1900s. By the 1960s, the river was clogged with pollution and declared ecologically dead. When Marion Stoddart moved to a town along the river in 1962, she was appalled. She approached the state about setting aside a “greenway” (trees running the length of the river on both sides), but the state wasn’t interested in buying land along a filthy river. So Stoddart organized the Nashua River Cleanup Committee and began a campaign to ban the dumping of chemicals and wastes into the river. The committee presented bottles of dirty river water to politicians, spoke at town meetings, recruited businesspeople to help finance a waste treatment plant, and began to clean garbage from the Nashua’s banks. This citizen’s campaign, coordinated by Stoddart, greatly aided passage of the Massachusetts Clean Water Act of 1966. Industrial dumping into the river is now banned, and the river has largely recovered.
A large, 86-square-kilometer freshwater lake east of Seattle, Lake Washington became surrounded by Seattle suburbs in the building boom following the Second World War. Be-
Cleaning up the Nashua River.
The Nashua River, seen on the left in the 1960s, was severely Polluted because factories set up along its banks dumped their wastes directly into the river. Seen on the right today, the river is mostly clean.
tween 1940 and 1953, a ring of 10 municipal sewage plants discharged their treated effluent into the lake. Safe enough to drink, the effluent was believed “harmless.” By the mid-1950s a great deal of effluent had been dumped into the lake (try multiplying 80 million liters/day? 365 days/year x 10 years). In 1954, an ecology professor at the University of Washington in Seattle, W. T. Edmondson, noted that his research students were reporting filamentous blue-green algae growing in the lake. Such algae require plentiful nutrients, which deep freshwater lakes usually lack-the sewage had been fertilizing the lake! Edmondson, alarmed, began a campaign in 1956 to educate public officials to the danger: bacteria decomposing dead algae would soon so deplete the lake’s oxygen that the lake would die. After five years, joint municipal taxes financed the building of a sewer to carry the effluent out to sea. The lake is now clean
Solving Environmental Problems
It is easy to become discouraged when considering the world’s many environmental problems, but do not lose track of the single most important conclusion that emerges from our examination of these problems-the fact that each is solvable. A polluted lake can be cleaned; a dirty smokestack can be altered to remove noxious gas; waste of key resources can be stopped. What is required is a clear understanding of the problem and a commitment to doing something about it. The extent to which U.S. families recycle aluminum cans and newspapers is evidence of the degree to which people want to become part of the solution, rather than part of the problem.
In solving environmental problems, the commitment of one person can make a critical difference. Biological literacy is no longer a luxury for scientists-it has become a necessity for all of us.
Lake Washington, Seattle.
Lake Washington in Seattle is surrounded by residences, businesses, and industries. By the 1950s, the dumping of sewage and the runoff of fertilizers had caused an algal bloom in the lake, which would eventually deplete the lake’s oxygen. Efforts to reverse this effect and clean up the lake were started by W. T. Edmondson of the University of Washington in 1956. The lake is now clean.
How Real Is Global Warming?
The controversy over global warming has two aspects. The first contentious issue is the claim that global temperatures are rising significantly, a profound change in the earth’s atmosphere and oceans referred to as “global warming.” The second contentious issue is the assertion that global warming is the consequence of elevated concentrations of carbon dioxide in the atmosphere as a consequence of the widespread burning of fossil fuels.
Resolution of the second issue requires detailed science and is only now reaching consensus acceptance. Resolution of the first issue is a simpler proposition, because it is, in essence, a data statement. The graph to the right displays the data in question, global air temperatures for the last century and a half. Temperature data is collected from measuring stations across the globe and averaged, as shown in the image below. The bars of the histogram represent mean yearly global air temperatures for each year since 1850. In order to dampen the effects of random year-to-year variations and so better reveal accumulating influences, the data are presented as an anomaly histogram (in an anomoly histogram, each bar presents the deviation of the value during that period from the average value determined for some standard period). In this instance, the anomaly histogram shows the deviation of each year’s global mean air temperature from the mean of these values observed over a standard 30-year period between 1961 and 1990.