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Population & the Land

Population & the Land

& the

Introduction Rates A Sustainable Society Modification of Natural Systems The Land Ethic The Biosphere & Biomes & Species Preservation Summary

Who cannot wonder at this harmony of things, at this symphony of which seems to will the well-being of the world? Cicero

Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio. A slight acquaintance with numbers will show the immensity of the first power in comparison with the second. Thomas Malthus Introduction

• Increasing human place increasing stresses on Earth’s finite resources. • It currently takes about 11 years to add a billion people to Earth. • Current global population is just over 6 billion.

English curate, Thomas Malthus, published a famous essay on population growth in 1798 in which he predicted that population size would grow faster than agricultural production resulting in a lack of future food supplies. Although Malthus correctly identified the upward trend of population growth, he did not anticipate concomitant advances in food production and resource extraction that would meet the physical and material needs of the burgeoning global population.

However, Malthus's basic observation remains true, population-related trends expand exponentially by a constant rate, for example, 2% per year, whereas agricultural trends typically increase arithmetically by a constant value, such as 2,000 tons per year (Fig. 1). For example, compare the rate of increase in irrigated farmland worldwide (three million hectares per year) with the growth in number of telephone lines (5% per year). The second section of this chapter considers how population growth rates have varied with time and the Figure 1. Arithmetic implications for global population distributions in the next vs. exponential increases. The area of irrigated farmland has increased by a near-constant value each year (~3 million hectares per year, an arithmetic increase), whereas the number of telephone lines increased at a constant rate (~5% per year, an exponential increase) century. since 1960. An exponential increase Population Distribution creates the concave- upward graph shown A third of the world’s population lives in just two countries, on the right, and , out of 227 nations, and just over half of the sometimes called a J- world's people live in six nations (Fig. 2; China, India, U.S., curve. , Brazil, and Russia).

2 Figure 2. Top twenty Concern over increasing population size has continued to the nations ranked by present. Ecologist, Paul Ehrlich, has written, “No geological population. Note that event in a billion years has posed a threat to terrestrial life most populous comparable to that of human .” Ehrlich sees a nations are located in or near the . finite world with a limited volume of resources that will be diminished more rapidly as populations grow. In contrast, economist Julian Simon suggests, “There is no meaningful limit to our capacity to keep growing forever.” Simon views human beings as the world’s greatest resource and anticipates that we will create new technologies to deal with problems associated with increasing population size. The fate of the world rests on how the growing population chooses how to use the planet's finite resources. In an ideal world, we would develop into a sustainable society, a society that satisfies its need for resources without jeopardizing the needs of future generations.

Current is over 6 billion and is updated daily at the U.S. Census Bureau website. The expansion of population has resulted in the growth of cities and the conversion of natural environments to agricultural lands. The fourth section of the chapter reviews some of the changes that we have made to the planet in the modification of natural systems resulting from population growth.

Conservationist Aldo Leopold viewed each person as a member of both the social community of people and the ecological community of plants, animals, and the land. He

3 termed this concept the land ethic, and we use his idea as a springboard to discuss humans impact on the other members of the biosphere in the final sections of the chapter. Leopold suggested that just as in society where we have certain obligations and privileges, we have similar constraints on our behavior as members of an ecological community.

Modern biology was born in the mind of Charles Darwin on the Galapagos (Fig. 3) in 1835. It was here that Darwin’s observation “that the different islands to a considerable extent are inhabited by a different set of beings” identified the concept of the that links organisms to specific physical environments. The penultimate section of the chapter reviews the characteristics of the biosphere including Figure 3. View of the flow of energy and nutrients between organisms and the Galapagos Islands physical environment. The Galapagos ecosystems of Darwin’s from space. Image time still exist but, like many elements of the biosphere, are courtesy of NASA. increasingly endangered by human activities. have been threatened by invaders such as goats, pigs, dogs, and rats, introduced to the islands following the arrival of Europeans in the sixteenth century. Recent programs have successfully removed invasive pests from some islands and the native vegetation has rebounded as a result.

The presence of increasing numbers of people, all attempting to improve their standard of living, places greater stress on the environment, not only from the perspective of resource use, but also from of air and water, and from the need to dispose of larger volumes of . To evaluate the impact of human activity on nature we must first identify the parameters that influence the distribution of specific associations of plants and animals at a regional scale. These associations are termed biomes and are composed of multiple interrelated ecosystems. The final sections of the chapter, ecosystems & biomes and biodiversity & species preservation review the major biomes of the world, the human activities that impact the natural order, and efforts to preserve species that are threatened by .

4 Population Growth Rates

• Global population is expected to stabilizeto between 10 to 11 billion because of declining population growth rates. • Population growth rates have been in decline since the early 1960s. • Population growth is dependent upon current population size and growth rate. • Current population growth rate is approximately 1.3%.

Seventy-eight million people are added to the planet annually, approximately the population of Vietnam (the world's 14th most populous nation). An additional billion people are added to the world's population every 12 to 13 years at current growth rates. At that rate, world population would be over 14 billion by the end of the next century. However, the good news is that population growth rates have declined by approximately a third in the last few decades. The continued decline in growth rates is expected to result in a global population of around 10 billion by the year 2100 (Fig. 4).

Figure 4. Graph of world population in the past and projected into the future. Note: the time scale increases in irregular intervals.

The Basics of Population Growth Population growth rates are determined by the balance between the number of people added to a nation's population by birth and immigration and the number who are lost through death or emigration.

Population = birth rate - death rate + immigration - emigration growth rate

Population growth in the U.S. is determined by: • Birth rate of 14 per 1,000 people. • Immigration of ~4 per 1,000 people. • Death rate of 9 per 1,000 people. • Emigration is negligible. • The U.S. population growth rate is 14 + 4 – 9 = 9 per 1,000 people, or 0.9%.

5 Without ongoing immigration, U.S. natural population growth rates would approach 0.5%. Population changes in individual nations may result from an influx or an outflow of refugees fleeing persecution. Over 22 million people were recognized as refugees by the United Nations (UN) in 1998. Approximately 2.6 million citizens of Afghanistan were displaced by internal conflicts. Many of these people fled to Iran which saw its population increase by 2 million. Pakistan, Germany, and the U.S. all saw their populations increase by over a million people the UN considered refugees.

Figure 5. Global population growth (red line) vs. selected growth rates. Note that population increased at low rates (0.5%) for the first quarter century and accelerated to faster average growth rates (1.5%) in recent years.

Life was relatively short and brutish for much of human history and death rates were close to birth rates so population increased relatively slowly until the 1900s. In some cases death rates exceeded birthrates during outbreaks of rapidly spreading fatal diseases such as the Black Death (plague) in medieval which caused global populations to decline. Global population reached 1 billion in the early 1800s. It took over a hundred years for the population to double to 2 billion in the late 1920’s. Death rates declined during the second half of the 20th century with the advent of modern medicine, better sanitation, and improved nutrition. Rapid population growth followed as the gap between birth rates and death rates widened. Global population passed the three billion people mark in 1960, accelerated to 4 billion in 1974, 5 billion in 1987, and reached six billion in October 1999 (Figs. 4, 5).

Demographers (people who study changing population trends) recognize four stages of population growth (Fig. 6): 1. Both birth rate and death rate are high in relatively primitive societies (e.g., pre-1800s); population growth rates are low.

6 2. Birth rates remain high and death rates decline as technology and health facilities improve; growth rates increase. 3. Birth rates decline and death rates remain low as populations become more affluent; growth rates decline. 4. Birth rate equals death rate and population growth rates are zero.

Figure 6. The four stages in population growth. Population growth rate is reflected in the height of the gap between the curves. In this example growth rate is ~30/1,000 people (3%).

Recently, cultural forces (, access to contraception, increased female literacy, higher earnings) have lead to a reduction in birth rates in many developed and developing nations. Thirty-two countries (e.g., , Italy, Russia), representing 40% of the global population, have Figure 7. World natural population growth rates that are at or below population growth zero. Fertility rates (number of children born per woman) in rates from 1950 these nations have declined to 2.1 or less and are now at or projected to 2050. below replacement reproduction levels where the number of During the "Great deaths balances the number of births. Birth rates have also Leap Forward" China fallen dramatically in many developing nations over the last tried to restructure its economy, sending millions of farm workers into factories to increase output. The result was that agricultural production fell and millions died of starvation. Image from the U.S. Census Bureau.

7 few decades. Fertility rates declined in Bangladesh, one of the world's most densely populated nations, from 7 in 1975 to 3.3 today.

Population Growth vs. Population Growth Rates The maximum world population growth rate (increase in population relative to current population) of 2.2% was recorded in 1963 when world population increased by 71 million people (Fig. 7). The maximum population growth (actual number of people added to the world) occurred in 1989 when population increased by 87 million people. This represented a 1.7% increase over the previous year. Both population growth rate and population size are important in determining how population increases.

A similar increase in population size can be obtained from a small population with a high population growth rate or a larger population with a smaller population growth rate (Fig. 8). For example, the population of Nigeria is 114 million and it increases at a rate of 3% per year, generating an annual population increase of 3.4 million people. In contrast Indonesia has nearly twice as many people (214 million) people and a growth rate of 1.5%. Consequently, Indonesia’s population increases by 3.2 million people per year. The population increase in both nations is almost the same but Nigeria’s growth rate is among the highest in the world, whereas Indonesia’s is more moderate.

The average global growth rate has since fallen to 1.3% but the range of growth rates varies from less than zero (population decreases) to over 3%. The difference between population Figure 8. Global population growth from 1950 to 2050. Similar growth rates can yield different population increases depending upon the current population; likewise, similar population increases may result from different population growth rates. Image modified from a U.S. Census Bureau graph.

8 growth rates will result in some nations changing rank in the future. Nations with high growth rates (Nigeria) will rise, whereas nations with low or negative growth rates (Japan, Russia) will inevitably fall in rank.

Population Nation Growth Rate Predicted Rank 1998 Rank 2020 1 China 0.9 1 2 India 1.7 2 3 United States 0.9 3 4 Indonesia 1.5 4 5Brazil 1.27 6 Russia -0.3 9 7 Pakistan 2.2 6 8 Bangladesh 1.8 8 9 Japan 0.2 11 10 Nigeria 3.0 5

Population growth rates are in decline but population size will continue to increase. Current population growth rates are relatively low but the population base is so large that it ensures a population increase of approximately 2 billion people in the next quarter century. Approximately 80% of the world’s population and 95% of the world’s population growth occurs in developing nations in Africa, , and Asia.

A Sustainable Society

• More people will result in greater stress on the environment because of an increasing demand for limited resources, increased risk for natural hazards, changes in natural systems, and greater potential for human-related hazards. • The impact of people on the environment may be measured at a range of scales from the local to global.

It is theoretically possible that Earth could support many times its current population but such speculation takes no account of the quality of lives people would be required to lead to ensure sufficient food (and other resources) for all. Increasing population will result in an increase in the demand for resources, the modification of natural systems, and greater numbers of people living in hostile environments (Fig. 9).

9 Living standards are likely to impose the greatest constraints on future population growth.

Increasing the population of people on planet Earth will have impacts at a range of scales: • Global concerns (, ). • National problems (soil , oil supply). • Regional issues (groundwater sources, air quality). • Local issues (pollution, waste disposal, ). Figure 9. Contrasting impact of human activity between the sparsely populated central Wyoming community of Hiland (that's it in the background) and the more densely populated city of Toronto, Canada. The human impact on Hiland is almost negligible in comparison to the When faced with a diminishing pool of resources, should it be changes in natural our objective to grab as much as we can as quickly as possible systems that occur in or should we deliberately use less on the premise that future association with generations may one day need these resources? Citizens and larger cities. governments of the developed nations in North America and Europe have protested loudly over the depletion of the tropical rain . Yet they rarely point out that little of the original forests of Europe and the United States remain. If a sustainable global future requires persuading individual nations like Brazil and Zaire not to mow down their own trees, how will these nations be compensated? Some developing nations may be able to use otherwise scarce resources as a stepping stone toward a more prosperous future. However, nations with less to offer can do little more than protest their imperiled status.

Current estimates suggest a maximum global population of over 10 billion people. In a finite world, how many people can the planet support? If we are to reach the of Earth (the maximum population with a given technology and social organization that Earth can support indefinitely) we will have to create a sustainable society.

10 When humans first glimpsed the Earth from space it was from the 8 spacecraft orbiting the Moon in December 1968 (Fig. 10). These early views of the planet from the inky darkness of space helped illustrate for many the unique wonders of the fragile environment we share on spaceship Earth. Our isolation in space emphasizes our reliance on our home planet's resources.

Because of their restricted land areas and limited resources, Figure 10. View of small nations may feel the effects of environmental Earth from space problems earlier than larger continental nations. Island taken by Apollo 8 residents must rely on the careful management of their finite astronauts. Image resource base to ensure a reasonable future for generations to courtesy of NASA. follow. The signs of environmental stress are apparent on many Pacific island nations that suffer from a lack of freshwater sources, pollution of coastal waters, lack of waste disposal sites, destruction of fish stocks, loss of biodiversity, and a shortage of suitable agricultural land (Fig. 11). Furthermore, not all potential problems can be solved by the island nations themselves.

Figure 11. Plantation on Kauai, Hawaii. Image courtesy of NOAA Photo Collection.

• The Maldive Islands in the eastern Indian lie a few meters above level and may submerge beneath the waves if global warming becomes reality. Unfortunately for their citizens, the Maldives and similar island nations, have little clout in the international political arena to force the developed nations to reduce their emissions, the ultimate cause of global warming. The Maldive islanders have little to offer except beachfront views and these are readily available elsewhere. • Both Easter Island (Fig. 12), in the southern Pacific Ocean, and Hawaii were settled 1,500 years ago by Polynesian islanders. A rich culture flourished on Easter Island before declining to the point of impoverishment by the time the first Europeans encountered the island in 1722. Visitors to the island marveled at the hundreds of massive

11 Figure 12. Left: Statue on Easter Island. Image courtesy of NOAA Photo Collection. Right: Relative locations of Hawaii, Easter Island, and Nauru in the Pacific Ocean

carved statues, relics of a once sophisticated culture that peaked at 7,000 inhabitants around 1400 A.D. The society was based around a culture of ancestor worship tied to the statues. The growing population had developed a non- sustainable lifestyle that stripped the island of timber, its principal resource, used for offshore (canoes), transportation (of 20-ton statues), fuel, and housing. When the timber was gone the culture collapsed, reverting to cannibalism and tribal warfare. The survivors lived in caves and scratched out a meager living by farming. • Native inhabitants of the tiny (22 km2) island nation of Nauru (Fig. 12) in the western Pacific Ocean became enriched by the of phosphate used to fertilize Australian farms. Unfortunately, the mining process destroyed much of the island interior (80%) making it unfit for any other purpose. Native residents, supported by royalties from mining, pay others to do the work and grow little of their own food. Islanders have low life expectancy (54 years) and high rates of diabetes linked to a poor diet rich in junk foods. Poor (non-sustainable) resource management has ensured that there will be few economic opportunities for future generations of islanders when the phosphate is exhausted.

The question for us on Earth is, Will we show the same poor stewardship for our planet as the residents of Easter Island and Nauru or will we have a more enlightened approach that considers the long-term consequences of our interactions with the environment?

12 Modification of Natural Systems

• 38% of Earth’s land surface has been domesticated. • Both the area of grain producing lands and grain production per person have declined in recent decades. • provide many benefits for the environment. • Over half of U.S. wetlands have been drained for or development.

The physical surface on which we live can represent an aesthetic, economic, and/or recreational resource. Land has long held a special place in American culture. Belting out a few verses of “America the Beautiful” should be enough to convince anyone of the significance of the connection between Americans and the land. The appeal of the New World to colonists was the availability of land for the common man. The United States grew by adding lands by purchase, by treaty, or by taking them in war. The nation’s early economic vitality was largely based upon resources from the land. Majestic unspoiled natural landscapes of the continent contrasted with overdeveloped and overpopulated European nations. The land, and how it was used, have been a source of inspiration and consternation for centuries.

Friction between economic forces that seek to use the land and cultural forces endeavoring to protect it continues to generate some of the most heated debates on environmental policy in America and elsewhere. Pressure to convert natural lands for agriculture and urbanization will only increase as population increases. Such increases are most acute in poor, densely populated nations that can’t afford the high cost of imports and must rely on their land base to generate food to sustain their people.

Domestication of Natural Lands Approximately 38% of Earth's surface has been "domesticated," converted to cropland, pasture, plantations, urban use, etc. The degree of domestication (Fig. 13) depends upon the land area, population of the country, and character of the landscape. Nations with relatively high population densities typically have more domestication of land. For example, the small Asian nation of Bangladesh has 81% domestication and 9.2 people per hectare. In contrast, the U.S. has a 45% domestication rate and only 0.3 people per hectare.

13 Figure 13. Domesticated land area as a proportion of land available for continents and selected nations. Bold values represent for selected continents.

(Note: a hectare = 2.5 acres.) However, some small nations with large populations have relatively low levels of domestication because of the rugged nature of their landscape (e.g., Japan).

Nation Land Area Population % (million (density per Converted hectares) hectare) Area United States 957 0.28 45 Brazil 846 0.19 28 Australia 764 0.02 60 India 297 3.25 61 Bangladesh 13 9.60 81

One of the most significant effects of increasing urbanization Figure 14. The city of and development is the loss of agricultural lands, especially Cleveland has lands that were originally situated close to cities and that were expanded to the east used to grow grain crops (Fig. 14). Approximately 1% of and west along the world’s land area is dedicated to urban uses and represents southern shore of home to nearly half (45%) of the world's population. Twenty- Lake Erie. six million hectares (approximately the area of Wyoming) are dedicated to urban uses in the U.S. Nearly half a million hectares (467,000) of in developing nations is lost annually to urbanization. More land is lost to the growth of cities in nations with rapidly expanding urban populations. Population growth rates vary for the world’s largest cities, but are typically higher in developing nations and in nations with rapidly growing economies (e.g., China).

Rank City Population Growth Rate (millions) (1990-95) 1 Tokyo, Japan 26.8 1.41% 2 Sao Paulo, Brazil 16.4 2.01% 3 New York, U.S. 16.3 0.34% 4 Mexico City, Mexico 15.6 0.73% 5 Bombay, India 15.1 4.22%

14 The total land area available for grain production has decreased in recent years but production has continued to increase because of the increased use of and improved farming techniques (Fig. 15). Unfortunately, population growth has increased more rapidly than grain production and grain production per person has declined for over a decade. Improved living standards have resulted in an increasing demand for grain to support "Western-style" diets that include grain-fed beef.

Figure 15. Changes in grain-producing area and grain production from 1965 to 1995.

Valuable agricultural lands are lost to expanding cities. The total area of land dedicated to growing grain crops has remained essentially static since the early 1970’s but grain production has risen because of increased use of fertilizers and improvements in agricultural methods.

Year World Grain World Grain World Grain Area (million Production Production per hectares) (million tons) Person (kilograms) 1955 639 759 273 1975 708 1237 303 1995 679 1703 299

The China Syndrome Improved living standards in developing nations have created a greater demand for meat and dairy products that are supplied by domestic animals fed a diet of grains. Grain production per person has steadily declined from a high of 342 kg in 1984 to less than 300 kg today. Continued declines in cropland area and increases in population will make it increasingly difficult for technological advances to meet the future demand for grain. Nowhere is this more evident than in China. China is undergoing a period of rapid industrialization as its economy is expanding rapidly. This economic boom is fueling a rise in living standards. Increasing affluence has meant more beef,

15 pork, poultry, and eggs are consumed, resulting in an increasing demand for grain to feed domestic .

Industrial expansion is gobbling up cropland, and contributing to a decline in grain production. In 1994, China was a net exporter of 8 million tons of grain, but in 1995 it became a net grain importer of 16 million tons. Some estimates suggest that Chinese grain imports will rise to at least 200 million tons by 2030. If China’s grain consumption per person increases to the level of Taiwan today, consuming even more livestock products, then grain imports may approach 400 million tons. However, the important question is: Who can supply grain on that scale? World grain exports are about 200 million tons per year, of which the U.S. supplies about half. If China becomes the 300-pound of world grain markets, other nations will either go hungry or go broke.

The Land Ethic

• Cultural forces are causing changes in Western views of land use. • Approximately a third of the U.S. is made up of federal lands. • The land ethic views each person as a member of an ecological community.

With the passage of the 1785 Land Ordinance, government lands were opened for public sale in tidy squares of 640 acres each. Unfortunately, land ownership didn't always ensure good stewardship. Since the nation’s earliest days, poor farming methods have often depleted the soil and degraded the land. While the nation was young and the western lands beckoned, few concerned themselves with soil conservation. The land seemed to stretch unlimited to the west in comparison to their European homelands.

Even as the nation expanded westward, there were large sections of the public domain that were never sold. Nearly a third of the nation is made up of federal lands administered by a variety of government agencies (National Park Service, NPS;

16 National Forest Service, NFS; Fish and Service, FWS; Bureau of , BLM). Much of this land may be leased for , grazing, or mining, or used for recreation. Of these public lands, the most heavily used are the national park system, which is made up of over 50 parks plus national historic sites, battlefields, parkways, recreation areas, , seashores, and monuments. Although the National Park Service was not created until 1916, the first lands were set aside for public use by congress in 1832, when four square miles of thermal springs were reserved near Hot Springs, Arkansas. It was in this same year that the artist, George Catlin, first wrote about “a nation's park” that would preserve the buffalo and the native cultures of the western plains. However, it was not until 40 years later, in 1872, that Congress authorized Yellowstone as the world's first national park.

Figure 16. National forest lands in the Black Hills, South Dakota

The relative remoteness of sites like Yellowstone meant that they were enjoyed by an affluent clientele and they earned a reputation as elitist vacation spots, until the advent of widely available motorized transportation in early 1900s. Today, there are more visitors to our national park system than there are people living in the U.S., and the parks suffer from the problems attendant with such overcrowding. In Yellowstone's earliest days, its principal environmental concern was poaching. Today, park officials must monitor many other problems, including (1) the development of surrounding lands which fragments ecosystems essential to park animals, (2) from abandoned (and potential future) mines on adjoining federal lands, (3) increasing numbers of confrontations between visitors and park animals, and (4) the use of thermal waters by others outside the park boundaries.

Historian, Frederick Jackson Turner, speaking at the 1893 Columbian Exposition in Chicago, suggested that the frontier had played a decisive role in creating the hallmarks of the American character. Turner believed that life on the frontier led to the development of personal traits such as pragmatism, individualism, materialism, nationalism, optimism, and democracy. Turner's view implied a type of social Darwinism

17 in which a niche was developed on the frontier for Bunyanesque characters forging an American identity.

This theme of individualism and the frontier spirit it generated has remained a constant theme in American art, literature, and politics. In recent years, some westerners have taken symbolic steps to demonstrate their opposition to the federal management of public lands. Most of the initiative (sometimes called wise use) comes from those using public lands for grazing, logging, mining, or oil exploration. The public appears sympathetic to those whose land values have been diminished by the effects of environmental legislation. Yet, they are more likely to choose protection of the environment over development or property rights issues, and a majority favor charging fees for grazing, drilling, mining, and logging on federal lands.

Aldo Leopold was born at the end of the Nineteenth century, into a time when people’s impact on natural systems was becoming clear. Leopold, a trained forester, published the conservation classic A Sand County Almanac and Sketches Here and There, in 1949. The book included his seminal essay, The Land Ethic, wherein Leopold presented an argument in favor of the preservation of all elements of nature, which he collectively considered as the land. The land ethic defined each person as a member of both the social community of people and the ecological community of plants, animals, and the land. He suggested that just as in society, where we have certain obligations and privileges, we have similar constraints on our behavior as members of an ecological community.

The Biosphere

• The biosphere represents all animal and plant life on Earth and the environments in which they live. • Ecology is the study of the interaction of organisms with each other and their environment. • The stability of ecosystems are influenced by a combination of abiotic and biotic factors.

18 • All organisms rely on the intake of energy from the Sun (plants) or through the consumption of plants (herbivores) and/or other animals (omnivores, carnivores). • Some elements serve as essential nutrients for life in plants and animals and move through the Earth system in biogeochemical cycles. • Most of Earth's biomass is concentrated in forests with tropical rain forests accounting for the most biomass per square kilometer.

The biosphere represents life on Earth and is confined to a relatively narrow strip of the planet's surface that extends from the deepest portion of the ocean floor to the Himalayas highest mountains. The diversity of life on Earth ranges among millions of species, from the simplest single-cell organisms to giant marine such as the blue whale. Ecology is the study of the interaction of organisms with each other and their environment. Communities of organisms that inhabit specific physical environments, defined primarily by their and landforms, make up ecosystems. Best estimates suggest that there are from 5 to 30 million species worldwide. Biodiversity, the number of species in an ecosystem, varies depending upon the characteristics of the individual ecosystems but is typically greatest in environments with warm temperatures, plentiful rainfall, and rich soils.

The stability of ecosystems are influenced by a combination of biotic (organic) and abiotic (non-organic, e.g., sunlight, precipitation) factors (Fig. 17). Where we choose to live is largely determined by the abiotic characteristics of our physical environment (e.g., climate, landscape) and the availability of basic resources such as food. Other organisms are little different. Individual abiotic factors may be limiting factors

Figure 17. Abiotic environmental factors that influence the distribution of ecosystems. The majority of species live within the upper 200 meters (660 feet) of the ocean (euphotic zone) and below 6200 m (20,500 feet) on land.

19 that can control the growth of an organism’s population in a given area. For example, water quality controls fish populations in acidified lakes in the Adirondack Mountains of New York. Reproduction in lake trout ceased as lakes became increasingly contaminated by acid precipitation because of upwind .

Plants are producers that manufacture the food they need from inorganic compounds in the physical environment. Through , most plants use light energy (from sunlight) to convert atmospheric gases (e.g., carbon dioxide), water, and soil nutrients into leaves, branches, and roots. Approximately 1% of solar radiation is used by plants for photosynthesis. The actions of each plant mimic the earth system in miniature. The atmosphere supplies key gases, the hydrosphere provides water, the solid earth is the source of the soil material and the plant itself represents the biosphere.

carbon dioxide + water + energy Æ glucose + oxygen from air from soil sunlight photosynthesis

Animals are consumers that can't produce their own food from inorganic materials, such as air or water, but derive their energy from consuming plants or other organisms and use the energy to grow and maintain tissue mass. Most of the energy represented by the plant material is lost by consumers as heat or is excreted from animals as waste. Primary consumers (herbivores, e.g., cows, deer) devour plants and secondary consumers such as wolves and humans eat primary consumers. The consumers and producers are part of a food chain that transfers energy between organisms within an ecosystem. Approximately 5 to 20% of energy is transferred with each step up the food chain. As energy is lost with each step, the numbers of organisms decrease with each step up the chain.

glucose + oxygen Æ carbon dioxide + water + energy from consumption from respiration of producers

Dead organisms are broken down and returned to their constituent inorganic materials (that will become nutrients for plants) through the actions of decomposers, for example, fungi and .

Certain key elements serve as essential nutrients for life in plants and animals. Six elements (nitrogen, carbon, hydrogen, oxygen, phosphorus, and sulfur) make up

20 approximately 95% of materials in plants and animals and combine to form compounds that are essential nutrients for life on Earth. These and other elements pass through the Earth system in biogeochemical cycles (Fig. 18) that link together processes in the biosphere, atmosphere, hydrosphere, and solid earth.

The amount of organic material in an ecosystem is the biomass and can be divided into phytomass (plants) and zoomass (animals). The vast majority (99%) of biomass is phytomass. Phytomass represents a reservoir for key elements of chemical cycles on Earth. Current debate over the role of tropical rain forests in sequestering carbon from the atmosphere and thus moderating the potential impact of the global warming illustrates how important it is to understand the distribution of biomass within the Earth system. Tropical rain forests represent a third of Earth's biomass but cover only 7% of the land surface. All of the planet's forests account for approximately three-quarters of all biomass on 20% of the land. In contrast, cover about the same land area but account for less than 2% of biomass

Figure 18. Biogeochemical cycles link some of the major elements of the Earth system including carbon (C), nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S).

21 Element Source Nutrients/compounds

Carbon (C) Air, water Carbon dioxide (CO2) Hydrogen (H) Water Water (H2O) Nitrogen (N) Air, water, soils Gas (N2), nitrate (NO3), ammonium (NH4) Oxygen (O) Air Carbon dioxide (CO2) Phosphorus (P) Water, soils Phosphate (PO4) Sulfur (S) Water, soils Sulfate (SO4)

The distribution of biomass is a proxy measure of biodiversity. The next section compares the characteristics of ecosystems and explores the role of human activity in reducing biodiversity.

Ecosystems & Biomes

• Ecosystems are communities of organisms that inhabit specific physical environments. • Biomes are composed of several ecosystems and represent a regional community of organisms named after the dominant vegetation. • The three major types of biomes are grasslands, forests, and . • Grasslands can be subdivided into savanna, temperate grasslands (prairie), and tundra with decreasing average temperature. • Forests receive more precipitation than other biomes and vary from boreal, to temperate, to rain forest with increasing temperature. • Deserts have the fewest species and the most extreme climate.

Effective management and care of the biosphere requires that we understand how organisms interact with the physical environment to create their . Management involves understanding the scale at which such associations function and the processes that control the distribution of species within such systems. Ecosystems are communities of organisms that inhabit specific physical environments, defined primarily by their climate and landforms. A number of similar ecosystems can be grouped together in a biome, a regional community of plants and animals named after the dominant type of

22 Figure 19. Nine global-scale biomes. Many ecologists would further divide grasslands or tropical forests into additional biomes or ecogregions. Map adapted from Miller, 1995, Environmental Science, ITP.

vegetation. Biomes are characterized by similar association of species, comparable , and consistent soil types (Fig. 19).

Ecologists don't agree on an exact number of ecosystems and biomes because the number will vary depending upon how they are defined (Which species are used? What climate characteristics are considered?). Much of the eastern U.S. is considered a biome (under natural conditions, prior to domestication) but it is composed of several separate eco-regions that include the eastern broadleaf forests of West Virginia, the southeastern mixed forest of the western Carolinas, and the coastal plain mixed forest of northern Florida. Generally we recognize three major climate-related biome groups, grasslands, forests, and deserts, each of which can be further subdivided into individual biomes (Fig. 20).

Figure 20. The distribution of biomes is largely a function of regional climate patterns. The transition between deserts, grasslands, and forest is governed by rainfall and different types of each biome are differentiated by temperature.

23 Grasslands Grasslands range from the high-temperature, low-moderate precipitation of the African savanna characterized by scattered trees, to the treeless, frigid plains of the tundra straddling the Arctic Circle in northern Asia and North America (Fig. 21). The Serengeti Plain of Kenya and Tanzania is the largest example of savanna grasslands and is home to the largest land animals such as the , rhino, and giraffe. The tundra is snow-covered for much of the year and its shallow soils and rocky surfaces support little more than grasses, sedges, and lichen that are adapted to the cold, dry climate. The extreme cold of the tundra environment results in a short growing season that barely stretches beyond two months. The environment is characterized by a few large species like the caribou that can migrate within the ecosystem and an of short-life-cycle .

The temperate grasslands are known by a variety of names, pampas in , prairie in North America, steppe in Figure 21. North Russia, and veldt in South Africa, yet all share common American grassland characteristics. All occur in continental interiors with cold environments. Left: winters and hot summers, they may have tall or short grasses Caribou feeding on depending upon precipitation (or the lack of it), and trees are tundra vegetation, Alaska. Image courtesy only found along waterways. Much of these original temperate of USFWS. Right: grasslands were converted to croplands, only to be devastated Tallgrass Prairie by wind erosion when wiped out crops poorly adapted National Preserve, to dry climate cycles. In the U.S. alone, over 100 million Flint Hills, northeast hectares of prairie is gone with only a few hundred acres left in Kansas. Less than isolated remnants in states like Iowa and Kansas (Fig. 21). 1% of original Bison, pronghorn antelope, and prairie dogs, were abundant tallgrass prairie throughout the prairies until the prairie became domesticated remains, most of it in and some species (bison, black-footed ferret) came close to the the Flint Hills. Image brink of extinction. courtesy of the U.S. NPS.

24 Forests Three principal forest biomes can be separated on the basis of the types of vegetation in each. Boreal forests (taiga) of northern latitudes are composed of coniferous evergreens (spruce, fir, pine) growing on acidic soils. Such environments are characterized by cold temperatures and low plant diversity. Moose, wolf, , and lynx are characteristic of boreal forest environments. Much of the eastern U.S. and northern Europe are covered by temperate forests dominated by broadleaf deciduous tree species (oak, sycamore, maple, poplar) that lose their leaves prior to their dormant winter season. The loss of leaves during fall provides nutrients for the underlying soils. Areas of especially high rainfall may be home to temperate rain forests (e.g., Pacific Northwest) with both evergreen and deciduous species, including the giant redwoods. The temperate forests are home to the tallest species on Earth, the coastal redwoods as well as animals such as , deer, and squirrel.

Figure 22. Rain forest destruction, Brazil. Dark areas show remaining rain forest. Vegetation has been destroyed by set to clear lands for slash-and-burn agriculture. Original image courtesy of NASA's EarthRISE database. Tropical rain forests dominate in areas of high temperature, high rainfall, plentiful sunlight, and high humidity at low latitudes adjacent to the equator. These forests are characterized by evergreen, broadleaf, hardwood trees such as mahogany, teak, and ebony and are home to the most diverse ecosystems on the planet. The forest is structured in three distinct layers (high, middle, lower canopies) the tallest of which tops out around 60 meters. The dense tree cover prevents light or winds from penetrating to the forest floor so much of the is accomplished by insects, including over 500 species of butterflies. The vertical character of the forest has resulted in the evolution of arboreal (tree-dwelling) species such as sloths, monkeys, and . Rapid weathering rates ensure thick soils but the soils lack nutrients because the vegetation doesn't lose leaves as in temperate environments. Approximately half the original tropical rain forest has been

25 destroyed (Fig. 22) to open lands for slash-and-burn agriculture that soon depletes the limited soil nutrients before cutting down more forest cover. In comparison the U.S. has lost approximately a third of its forested land area since the 1600s.

Deserts Dry climates are characterized by hot and cold deserts and semi-desert environments such as chaparral. These environments are home to plants adapted to conserve water (long roots, succulent tissues) and burrowing animals that know enough to stay out of the sun. Hot deserts have high temperatures throughout the year and are home to a few plants that cling to life on a substrate of sand or rock (e.g., Sahara, North Africa). Cacti are relatively common in temperate deserts that have hot summers but cool winters (e.g., Mojave Desert, southeast California; Fig. 23). Animals are rare in desert environments but camels, scorpions, and the kangaroo rat have adapted to life in such extreme conditions. Figure 23. Saguaro cactus, southwestern Chaparral, also known as Mediterranean , is U.S. Image courtesy of characterized by dry summers but has a similar total rainfall as USFWS. some temperate grasslands. It contains woody shrubs and may have grassy woodlands with species such as the cork oak, olive, and eucalyptus trees.

Mountains Mountains represent a special case as their increasing elevations have the same effect as increasing latitude. Temperatures decline and precipitation increases as both elevation and latitude increase. Equatorial mountain (alpine) biomes are characterized by tundra vegetation at high elevations and descend through coniferous (boreal), deciduous (temperate), and tropical (rain) forests with decreasing altitude.

26 Biodiversity & Species Preservation

• Species loss is most commonly attributed to the destruction of . • There are three basic reasons to preserve species: (1) Practical - species benefit mankind; (2) ecological - for maintenance of biological systems; (3) aesthetic - to preserve the natural environment for human enjoyment. • The Act was passed in attempt to protect species of aesthetic, ecological, educational, historical, recreational, and scientific value.

Loss of Biodiversity Few biomes remain in their original state today as many have been modified by a variety of human activities. Environmental changes may be slow or rapid and may occur at local, regional or national scales. Natural environments change as human activity intrudes into an otherwise pristine environment (Fig. 24). Natural vegetation is cleared to create land for crops and/or grazing. The loss of natural lands to agriculture or urbanization inevitably results in habitat destruction and may be accompanied by predator control efforts to reduce populations of species (e.g., wolves) considered a threat to domestic animals or the human population.

As human populations continue to increase, the impact on the living resources of the biosphere may become more severe. Westward expansion and ready access to rifles resulted in a 99.99% reduction in buffalo herds on the Great Plains in the second half of the nineteenth century. Today has depleted the majority of the world's commercial fisheries. Even Figure 24. A relatively benign activities such as tourism result in resourceful osprey environmental alterations as and buildings are finds an constructed to meet the demands of travelers. International unconventional travel has aided the introduction of alien species into nesting site on this environments where they replace native organisms. Human channel marker in activities such as farming, mining, or industrialization may Kentucky Lake. introduce pollutants into the environment that have a profound effect on ecosystems. For example, the Exxon Valdez tanker spilled millions of gallons of oil of the south of Alaska in 1989, destroying coastal marine habitats.

27 Preserving Endangered Species We have long recognized that human development inevitably leads to declines in wildlife populations. Awareness of decreasing wildlife populations prompted the formation of several conservation organizations among hunters and fueled efforts to create federal regulations to prevent the exploitation of game species. The federal government would later introduce legislation to form wildlife refuges, reservations, forest reserves, and wilderness areas (preserving habitat). More recently, habitat destruction and pollution have replaced as the primary cause of species decline in many parts of the world. The destruction of habitat is the prime reason why species go into decline. Maintaining natural habitat for wildlife became increasingly difficult as the human population grew and as the nation’s transportation infrastructure expanded, making almost the whole continent accessible. It is estimated that we lose over 200 acres of land in the U.S. each hour to development.

Given that there are millions of species on Earth and that more than 99% of all species that ever lived are now extinct, it may seem that the loss of a few additional organisms (Fig. 25) as a result of human activity is a small and relatively insignificant price to pay for progress. There are three basic reasons given to counter this position:

• Practical: Certain species benefit human beings by providing resources essential for our present or future existence. The most basic examples are species that are harvested for food, but many others are used for pharmaceuticals and those currently threatened by extinction may have yet undiscovered benefits including cures for human ailments. The rosy periwinkle, a plant found only on that contains organic compounds that have been used to help treat cancer, is today threatened by habitat destruction. There are approximately 80,000 edible plant species and we use just three (corn, wheat, rice) to provide half the world's food supply. Wild relatives of common crops represent a reservoir of genetic material that we can dip into to create disease-resistant strains of domesticated species. • Ecological: Although some organisms have no direct benefit to humans they are essential to maintaining the order of the biosphere. The web of life is a complex system with the life cycles of hundreds or thousands of species

28 tightly intertwined. Taking out one species is like removing an organ from the human body. Sometimes we can continue to operate efficiently with the loss because there is some redundancy built into our anatomy (e.g., kidney, lung) but a malfunctioning liver or heart can result in the collapse of the whole body. Threatened or endangered species such as the northern and marbled murrelet in the old-growth forests of the Pacific Northwest may be considered a signal of a decline in this ecosystem resulting from . • Aesthetic: Almost everyone derives some pleasure from experiencing nature. The sales of nature calendars alone tell us that people like to look at scenes that reflect the processes of the biosphere. The 280 million people that visit our national park system annually do so to appreciate the physical environments created by natural processes. Anyone who has ever paused to appreciate the changing colors of a woodland on a fall day has recognized the artistry of nature. Many recreational activities (e.g., hiking, climbing, hunting, fishing, canoeing, swimming, gardening) are intimately linked to the natural world around us and would be diminished by the loss of the elements that contribute to the biosphere.

Figure 25. Four examples of threatened or endangered species on the Endangered Species List. Clockwise from top left: Karner Blue butterfly; ; Black-footed ferret; and Dwarf lake iris. Images courtesy of U.S. FWS.

The primary law used to protect species today is the Endangered Species Act (ESA), perhaps the most unpopular piece of federal environmental legislation - at least among some developers. The ESA, passed in 1973, declares it illegal to harass, harm, pursue, shoot, wound, kill, trap, capture, or collect listed species.

29 The goal of the ESA is to protect species long enough so that they can undergo recovery, at which point they can be removed from the Endangered Species List. Recent success stories for the Pacific Gray whale and bald eagle have resulted from restrictions on human activities including a ban on worldwide commercial whaling and the elimination of the use of the pesticide DDT in North America, respectively. However, such successes are relatively rare. Less than 2% of species have been removed from the endangered list and about a third of those were declared extinct.

Summary

1. What is the difference between exponential and arithmetic growth? Exponential growth occurs at a constant rate (e.g., 5%) whereas arithmetic growth increases by a constant amount (e.g., 5 acres per year). Exponential growth will be the most rapid. Imagine two people who each run 1 km a day for exercise. Person A decides to increase the distance they run by 100 meters per day. Person B decides to increase their distance by 10% of the previous day's run (don't ask why, they just really love math). After 10 days, A is running 2 km and B is running 2.6 km. Ten days later A covers 3 km but B must run 6.7 km to keep on pace. After another 10 days, A runs 4 km and is feeling pretty good but B has to run over 17 km and must run nearly 2 km further each day just to keep on their exponential pace. B gives up and changes his exercise routine to include eating donuts and watching football on his big-screen TV.

2. How many people are there in the world and where do they live? The current global population is a little over 6 billion and is increasing by 78 million people each year. Most of these people live in Asia. China and India have over 2.2 billion people between them and 12 of the 20 most populous nations are in Asia (3 in Africa, 1 in South America, 2 in Europe, 2 in North America). The U.S. is a long way behind India but it is the third most heavily populated country in the world. 3. How is population growth determined?

30 Population growth worldwide is the balance between global birthrates and death rates. As births exceed deaths, population is increasing at a rate of 1.3% per year. National growth rates also include emigration (people leaving a country) and immigration (people coming to a country). Approximately a third of U.S. population growth is accounted for by immigration. Political or economic refugees may cause short- term fluctuations in a nation's population growth rate.

4. How have population growth rates changed with time? Population growth rates typically have four possible configurations: (a) birth rate and death rate are both high and population growth rates are low; (b) birth rates are high and death rates decline, growth rates increase; (c) birth rates decline and death rates remain low, growth rates decline; (d) birth rate equals death rate and population growth rate is zero. Global population passed through the second stage during the first half of this century and most of the world is now in the third stage. Several nations (e.g., Italy, Japan) have reached the fourth stage. Consequently, global population growth rates continue to decline from a high of 2.2% during the early 1960s to a current value of 1.3%.

5. What is the difference between birth rate, fertility rate, and population growth rate? Birth rate is the number of births per 1,000 people in a year. Birth rates worldwide range from approximately 8 to 30/1,000. The greater the difference between birth rate and death rate, the more rapid the population growth rate. Fertility rate represents the number of children born per woman. A fertility rate of 2 ensures parents are replaced by their children. Higher rates result in population increases, lower rates cause population declines.

6. Does a high population growth rate mean rapid population growth? Not necessarily. Population growth is dependent upon both the size of the existing population and the growth rate. Thus annual population growth was less (71 million) in the early 1960s than today (78 million) even though growth rates were higher (2.2% vs. 1.3%) because global populations were smaller (~3 vs. 6 billion).

7. Where are population growth rates highest and lowest? Population growth rates are highest in the developing world (e.g., Nigeria, 3%) and lowest in developed nations (e.g., Italy,

31 0%). Consequently, 95% of the people added to the world's population will be born in developing nations.

8. What is the carrying capacity of Earth? Good question. The carrying capacity is the maximum population that Earth can support indefinitely. The answer is probably anything between 6 to 20 billion depending upon the standard of living we are willing to "enjoy." Human population is expected to stabilize around 10 billion, essentially a self- imposed limit dictated by cultural standards.

9. Do we have a sustainable society now? Do you use anything that is not renewable? The petroleum products that allow us to drive our (or airplanes) or heat our homes, the coal that is burned to generate our electricity; both of these energy sources are non-renewable. Forests and fish should be renewable on the human time-scale but both have been substantially diminished in this century. The Atlantic cod fishery off Nova Scotia collapsed due to overfishing, despite warnings that it would happen. Tropical are being burned as you read this, those trees are not coming back any time soon. In short, we are some distance away from being a sustainable society and we are not likely to get close without the threat of more drastic shortages than is apparent now.

10. Why didn't the people of Easter Island recognize what was inevitably going to happen to their society? Each generation focused on its own needs and ignored the long-term consequences of their actions. Much of what they did was influenced by the cultural norms of their society that emphasized the need to make their big-headed statues.

11. What is "domesticated" land? Over a third of Earth's land surface has been domesticated, that is, it has been converted from its natural state to cropland, pasture, forest plantations, or urban use.

12. What factors influence the degree of domestication? Domestication is influenced by , the character of the landscape and climate, and the rate of growth of urban areas. Nations with relatively high population densities typically have more domestication of land unless the landscape is too rugged to support development or the climate is too extreme to support human life. Lands surrounding rapidly growing cities are most susceptible to domestication.

32 Urban growth rates are typically higher in major cities in developing nations.

13. How has domestication influenced agricultural production? Initially, natural lands were converted to agricultural lands and production expanded. However, those same croplands and pastures are now being consumed under expanding cities. The land area available for grain production has decreased over the last few decades but agricultural yields increased because of improvements in technology and increased use of fertilizers. Population has increased more rapidly than grain production so production per person is now actually less than in the past.

14. What is the land ethic? The land ethic defines each person as a member of the ecological community of plants and animals, or collectively, the land. Aldo Leopold suggested that just as in society, where we have certain obligations and privileges, we have similar constraints on our behavior as members of an ecological community. The land ethic views our role as stewards of the natural world.

15. What is the biosphere? Earth is composed of several components, including the hydrosphere (all waters, mainly the ), atmosphere (all air, from Earth's surface to space), and the biosphere (all life on Earth from bacteria to ). The biosphere is interwoven with other components of the Earth system. Most life occurs in the shallow oceans and at relatively low elevations on the land surface but even in extreme conditions of the deep ocean floor or the frozen poles, some organisms manage to survive.

16. What controls the distribution of life in the biosphere? Life is limited by abiotic factors such as temperature and precipitation that characterize the physical environment. These conditions are independent of organic activity. Life is most abundant in environments with plentiful supplies of key abiotic components and is least abundant in regions with extreme conditions.

17. How are energy and nutrients transferred from the physical environment to plants and animals? Plants use energy from the Sun to generate mass through photosynthesis. They absorb key nutrients from water and soils. Animals (consumers) eat the plants, thus receiving some of the stored energy and nutrients, and may in turn be eaten by

33 other animals. Key elements cycle through the biosphere through a series of biogeochemical cycles involving processes such as respiration, photosynthesis, weathering, and rock formation.

18. What is the relationship between biomass and biodiversity? Biodiversity represents the variety of species and biomass is the amount (mass) of material in part or all of the biosphere. Increasing biodiversity typically is reflected in increasing biomass, therefore, biomass per unit area can be used as an approximate measure of biodiversity.

19. What is the difference between a biome and an ecosystem? The difference is mainly one of scale. Biomes are bigger than ecosystems. Ecosystems are communities of organisms that inhabit specific physical environments, whereas, biomes represent collections of ecosystems and are regional or international in scale. Biomes are characterized by similar association of species, comparable climates, and consistent soil types.

20. What are the major biomes? Biomes can be loosely divided into three major groups, grasslands (savanna, temperate, tundra), forests (rain, temperate, boreal), and deserts. These major groups are divided by precipitation (more in forests, less in deserts) and are subdivided by temperature (low temperature in boreal forests and tundra; high temperatures in rain forests and savanna). Some biomes may be transitional between the major biomes, for example, chaparral occurs around the Mediterranean Sea and is defined by dry summers and may contain grasslands or .

21. What causes biodiversity to decrease? Biodiversity can gradually decrease due to natural changes in the physical environment but typically occurs more rapidly as a result of human activity. Human actions such as agricultural practices, commercial fishing, hunting, predator controls, pollution, and tourism can destroy natural habitats and reduce biodiversity.

22. What steps can be taken to preserve biodiversity? Actions that ensure the preservation of natural habitats have the greatest effect in preserving species because habitat destruction is the primary cause of . Habitat preservation can occur through private or corporate programs, or through

34 government agencies that preserve forest lands (although these agencies also oversee logging), national parks, and wildlife refuges.

23. Why should we care to preserve biodiversity? There are three principal reasons why we might consider it a good idea to minimize species loss. First, for purely self- centered reasons, we want to preserve species to help ourselves. Domesticated plants and animals provide us with the majority of our food resources. Related wild species represent a genetic resource that can be used to improve domestic species. The majority of species have yet to be formally described, consequently, their potential for human benefit is unknown. Relatively rare plant species provide us with treatments for serious diseases. Second, we don't know what role most species play in the functioning of the biosphere yet we know we like the idea of having a biosphere so logic suggests we shouldn't do anything to meddle with the natural order of life. Finally, much human enjoyment is derived from the simple pleasures of observing life on Earth. By preserving all elements of the biosphere, we preserve a source of delight for the generations that will follow us.

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