populations and the use of natural resources chapter 27

Populations and Populations and the use of Natural the use of Natural

ResourcesResourcesChapter 27Chapter 27

– Most organisms are adapted to their Most organisms are adapted to their immediate environment; they live in a balance immediate environment; they live in a balance with the natural resources their environment with the natural resources their environment provides.provides.

– Some organisms alter their environment to Some organisms alter their environment to better meet their needs.better meet their needs.

Resources and Resources and OrganismsOrganisms

All organisms need particular natural resources All organisms need particular natural resources such as air, food, water, and, in some cases, such as air, food, water, and, in some cases,

shelter to maintain life, grow, and reproduce.shelter to maintain life, grow, and reproduce.

Resources and Resources and Population GrowthPopulation Growth

As any population increases, its demand for As any population increases, its demand for natural resources increases as well. natural resources increases as well.

ExponentialExponential growthgrowth is a pattern of growth in is a pattern of growth in which a population grows faster as it increases in which a population grows faster as it increases in size, resulting in a population explosion.size, resulting in a population explosion.

Resources and Resources and Population GrowthPopulation Growth

This graph shows This graph shows a rapid increase a rapid increase over time in the over time in the population of population of bacteria after just bacteria after just a few individuals a few individuals were added to a were added to a petri dish full of petri dish full of nutrients. Note nutrients. Note the J-shaped curve the J-shaped curve of the graph.of the graph.

Limits to Population Limits to Population GrowthGrowth

Eventually, one or more Eventually, one or more limiting factorslimiting factors, such as , such as the availability of food, water, or clean air, will the availability of food, water, or clean air, will cause a population to stop increasing. cause a population to stop increasing.

Carrying capacityCarrying capacity is the number of organisms is the number of organisms that any given environment can support.that any given environment can support.

A population that is at the carrying capacity for its A population that is at the carrying capacity for its environment is in equilibrium and will remain so environment is in equilibrium and will remain so as long as natural resources are available.as long as natural resources are available.


Under normal Under normal conditions, populations conditions, populations usually reach an usually reach an equilibrium with the equilibrium with the resources available resources available in the environment. in the environment. From that point on, From that point on, the population size the population size will fluctuate around will fluctuate around the carrying capacity. the carrying capacity.


Environmental LimitsEnvironmental Limits– Density-independent factorsDensity-independent factors are are

environmental factors, such as storms, environmental factors, such as storms, droughts, and pollution, that affect all droughts, and pollution, that affect all populations that they come in contact with, populations that they come in contact with, regardless of population size.regardless of population size.

– Density-dependent factorsDensity-dependent factors are are environmental factors, such as disease, environmental factors, such as disease, parasites, and lack of food, that increasingly parasites, and lack of food, that increasingly affect a population as the population’s size affect a population as the population’s size increases. increases.

Human Population Human Population GrowthGrowth

A graph of human population growth still shows a J-shaped curve. A graph of human population growth still shows a J-shaped curve.

Human Impact on Land Human Impact on Land ResourcesResources

Each year, a typical person in North America Each year, a typical person in North America consumes resources equal to the renewable yield consumes resources equal to the renewable yield from approximately 5 ha (about 12.35 acres) of from approximately 5 ha (about 12.35 acres) of forest and farmland. forest and farmland.

Through our use of mineral resources, food, Through our use of mineral resources, food, lumber, and living space, humans have a lumber, and living space, humans have a significant impact on Earth’s surface.significant impact on Earth’s surface.

Extraction of Mineral Extraction of Mineral ResourcesResources

Modern societies require huge amounts of land Modern societies require huge amounts of land resources, including iron, aluminum, copper, resources, including iron, aluminum, copper, sand, gravel, and limestone. sand, gravel, and limestone.

Finding a balance between the need for mineral Finding a balance between the need for mineral resources and controlling the environmental resources and controlling the environmental change caused by extraction can be difficult.change caused by extraction can be difficult.


Underground MiningUnderground Mining– Underground mining, also called subsurface mining, Underground mining, also called subsurface mining,

is used where mineral resources lie deep under the ground. is used where mineral resources lie deep under the ground. – Underground mining is less disruptive to Earth’s surface than surface mining, but it still has impacts on the Underground mining is less disruptive to Earth’s surface than surface mining, but it still has impacts on the

environment. environment.


Surface MiningSurface Mining– Mineral and ore deposits found just beneath Earth’s surface can be extracted by removing huge amounts of overlying Mineral and ore deposits found just beneath Earth’s surface can be extracted by removing huge amounts of overlying

soil and rock. soil and rock. – Mining in this way completely changes the landscape.Mining in this way completely changes the landscape.– ReclamationReclamation is the process of restoring the land to its original contours and replanting vegetation. is the process of restoring the land to its original contours and replanting vegetation.

AgricultureAgriculture BiodiversityBiodiversity refers to the biological diversity of refers to the biological diversity of

an ecosystem, which is determined by the variety an ecosystem, which is determined by the variety of species of plants and animals.of species of plants and animals.

Ecosystems that have high biodiversity are more Ecosystems that have high biodiversity are more stable than those with fewer species.stable than those with fewer species.

AgricultureAgriculture

MonocultureMonoculture– When land is cleared for food production, a biologically diverse ecosystem is often replaced with a single plant When land is cleared for food production, a biologically diverse ecosystem is often replaced with a single plant

species, such as corn or wheat. species, such as corn or wheat. – MonocultureMonoculture is the planting is the planting

of just one species in a field. of just one species in a field.

– Growing a monoculture crop is an Growing a monoculture crop is an efficient farming method, but it is more efficient farming method, but it is more susceptible to disease than other crops.susceptible to disease than other crops.


PesticidesPesticides– Pesticides, including fungicides and insecticides, have played an important role Pesticides, including fungicides and insecticides, have played an important role

in boosting food production worldwide by eliminating organisms that destroy in boosting food production worldwide by eliminating organisms that destroy crops. crops.


TopsoilTopsoil– It can take thousands of years for topsoil to form, and thus, once it is lost, it is hard to replace. It can take thousands of years for topsoil to form, and thus, once it is lost, it is hard to replace. – Erosion of topsoil occurs when forests or grasslands are cleared for the first time. Erosion of topsoil occurs when forests or grasslands are cleared for the first time. – The addition of fertilizers helps replace some of the nutrients that are depleted by topsoil erosion, but they cannot provide all of the lost substances. The addition of fertilizers helps replace some of the nutrients that are depleted by topsoil erosion, but they cannot provide all of the lost substances. – Methods used by farmers to selectively apply fertilizers where they will provide the greatest benefit include soil analysis, careful mapping of fields, and Methods used by farmers to selectively apply fertilizers where they will provide the greatest benefit include soil analysis, careful mapping of fields, and

monitoring of plant growth. monitoring of plant growth.

ForestryForestry Worldwide, thousands of hectares of forests are Worldwide, thousands of hectares of forests are

cut down annually to meet the demand for cut down annually to meet the demand for firewood, charcoal, paper, and lumber. firewood, charcoal, paper, and lumber.

DeforestationDeforestation is the removal of trees from a is the removal of trees from a forested area without adequate replanting.forested area without adequate replanting.

Deforestation often involves clear-cutting, the Deforestation often involves clear-cutting, the complete removal of all the trees in an area.complete removal of all the trees in an area.

ForestryForestry The negative environmental impacts of The negative environmental impacts of

deforestation can be minimized through the deforestation can be minimized through the practices of selective logging, and the retention of practices of selective logging, and the retention of buffer zones of trees along streambeds.buffer zones of trees along streambeds.

Urban DevelopmentUrban Development An estimated 5 billion people worldwide will be An estimated 5 billion people worldwide will be

living in cities and towns by the year 2025.living in cities and towns by the year 2025.

The development of land for the growth of urban The development of land for the growth of urban areas has many impacts on the environment. areas has many impacts on the environment.

– Natural habitats are lost as forests are cleared Natural habitats are lost as forests are cleared and wetlands are filled to provide land. and wetlands are filled to provide land.

– During construction, erosion of topsoil often During construction, erosion of topsoil often increases until new landscaping can be increases until new landscaping can be established.established.

Urban DevelopmentUrban Development– Concrete and asphalt coverage prevents groundwater Concrete and asphalt coverage prevents groundwater

supplies from being recharged and increases flooding.supplies from being recharged and increases flooding.

– Increasing urbanization produces large Increasing urbanization produces large volumes of solid waste which is often buried in volumes of solid waste which is often buried in landfills. landfills.

– Contamination of soil and groundwater with Contamination of soil and groundwater with heavy metals and poisonous chemicals occurs heavy metals and poisonous chemicals occurs as a result of industrial processes.as a result of industrial processes.

Urban DevelopmentUrban DevelopmentThis graph shows the percentage of This graph shows the percentage of solid waste generated by various users solid waste generated by various users of natural resources in the United of natural resources in the United States annually. Municipal wastes States annually. Municipal wastes are those wastes are those wastes contributed by homes and businesses.contributed by homes and businesses.

Urban DevelopmentUrban Development

SolutionsSolutions– Most environmental problems that urban Most environmental problems that urban

development creates can be solved.development creates can be solved. Barriers can be placed around construction sites to catch sediment from increased erosion. Barriers can be placed around construction sites to catch sediment from increased erosion. In the United States, wetlands are now recognized In the United States, wetlands are now recognized

as valuable ecosystems and are protected from development. as valuable ecosystems and are protected from development. Modern landfills are carefully designed to minimize leakage of toxic liquids. Modern landfills are carefully designed to minimize leakage of toxic liquids.

Urban DevelopmentUrban Development

SolutionsSolutions– Several methods are available for cleaning up industrial Several methods are available for cleaning up industrial

toxic-waste sites. toxic-waste sites. Contaminated soil can be removed and incinerated at temperatures high enough to destroy the toxic chemicals. Contaminated soil can be removed and incinerated at temperatures high enough to destroy the toxic chemicals. BioremediationBioremediation, which has , which has

been especially useful for been especially useful for contamination caused by contamination caused by spilled gasoline and oil, is spilled gasoline and oil, is the use of organisms to the use of organisms to clean up toxic wastes.clean up toxic wastes.

Human Impact on Air Human Impact on Air ResourcesResources

SmogSmog is a photochemical haze caused by the is a photochemical haze caused by the action of solar radiation on an atmosphere action of solar radiation on an atmosphere polluted with hydrocarbons and nitrogen oxides polluted with hydrocarbons and nitrogen oxides mostly from automobile exhaust systems. mostly from automobile exhaust systems.

OzoneOzone (O (O33), the major chemical in smog, is a gas ), the major chemical in smog, is a gas molecule made up of three oxygen atoms.molecule made up of three oxygen atoms.

– Ozone is beneficial in the upper atmosphere Ozone is beneficial in the upper atmosphere because it absorbs and filters out harmful because it absorbs and filters out harmful ultraviolet (UV) radiation. ultraviolet (UV) radiation.

– Ground-level ozone irritates the eyes, noses, Ground-level ozone irritates the eyes, noses, throats, and lungs of humans, and it also has throats, and lungs of humans, and it also has harmful effects harmful effects on plants. on plants.

Human Impact on Air Human Impact on Air ResourcesResources

Air pollution also occurs in the form of Air pollution also occurs in the form of particulate matter ranging in size from particulate matter ranging in size from microscopic bits to large grains.microscopic bits to large grains.

Particulates can lodge in lung tissues and cause Particulates can lodge in lung tissues and cause

breathing difficulties and lung disease.breathing difficulties and lung disease.

Global Impacts of Air Global Impacts of Air PollutionPollution

Global WarmingGlobal Warming– The greenhouse effect is a natural phenomenon in which Earth’s atmosphere traps heat in the troposphere to warm The greenhouse effect is a natural phenomenon in which Earth’s atmosphere traps heat in the troposphere to warm

Earth. Earth.

– Global warmingGlobal warming, a phenomenon related to the greenhouse effect, is an increase in Earth’s average surface , a phenomenon related to the greenhouse effect, is an increase in Earth’s average surface temperature. temperature.

– Human activities, especially the burning of fossil fuels, are largely responsible for Human activities, especially the burning of fossil fuels, are largely responsible for increased levels of carbon dioxide, which is the main greenhouse gas that causes increased levels of carbon dioxide, which is the main greenhouse gas that causes global warming. global warming.


Global WarmingGlobal WarmingThe amount of atmospheric The amount of atmospheric carbon dioxide has carbon dioxide has increased greatly since the 1850s.increased greatly since the 1850s.


Global WarmingGlobal Warming– Earth’s mean surface temperature has risen about Earth’s mean surface temperature has risen about

0.5°C in the last century. 0.5°C in the last century. Some scientists predict it may rise by 1 to 3.5°C in the next 100 years as a result of global warming.Some scientists predict it may rise by 1 to 3.5°C in the next 100 years as a result of global warming. Other scientists argue that the increase in Earth’s temperature could be part of a natural pattern of Other scientists argue that the increase in Earth’s temperature could be part of a natural pattern of

climatic change.climatic change.


Ozone DepletionOzone Depletion– The ozone layer serves as a protective shield as it absorbs and filters out harmful UV radiation.The ozone layer serves as a protective shield as it absorbs and filters out harmful UV radiation.

– Chlorofluorocarbons (CFCs), which were previously used in refrigerators, cleaning agents, and Chlorofluorocarbons (CFCs), which were previously used in refrigerators, cleaning agents, and as propellants in aerosol cans, used to contribute to ozone destruction in the upper atmosphere.as propellants in aerosol cans, used to contribute to ozone destruction in the upper atmosphere.


Ozone DepletionOzone Depletion– Since the mid-1980s, atmospheric studies have detected a thinning of Since the mid-1980s, atmospheric studies have detected a thinning of

the ozone layer, including an “ozone hole” over Antarctica. the ozone layer, including an “ozone hole” over Antarctica.

– Ozone depletion is entirely a result of human activity.Ozone depletion is entirely a result of human activity.– The Montreal Protocol, which 186 countries had signed by 2003, calls for a phase-out in the production and use of most ozone-The Montreal Protocol, which 186 countries had signed by 2003, calls for a phase-out in the production and use of most ozone-

destroying chemicals by developed countries by the year 2005 and developing countries by the year 2015.destroying chemicals by developed countries by the year 2005 and developing countries by the year 2015.– Based on current trends in data, the return to pre-1980 ozone amounts over Antarctica is expected by the middle of this century.Based on current trends in data, the return to pre-1980 ozone amounts over Antarctica is expected by the middle of this century.


Acid PrecipitationAcid Precipitation– Acid precipitationAcid precipitation is precipitation with a pH of less is precipitation with a pH of less

than 5.0. than 5.0. – Acid precipitation forms when sulfur dioxide and nitrogen oxides combine with atmospheric moisture to create Acid precipitation forms when sulfur dioxide and nitrogen oxides combine with atmospheric moisture to create

sulfuric acid and nitric acid. sulfuric acid and nitric acid.

– Although volcanoes and marshes add sulfur gases to the atmosphere, 90 percent of the sulfur emissions in eastern Although volcanoes and marshes add sulfur gases to the atmosphere, 90 percent of the sulfur emissions in eastern North America are of human origin.North America are of human origin.


Acid PrecipitationAcid PrecipitationAutomobiles are the greatest source of Automobiles are the greatest source of the nitrogen oxides that cause acid the nitrogen oxides that cause acid precipitation. Electrical utilities produce precipitation. Electrical utilities produce most of the sulfur dioxide. most of the sulfur dioxide.


Acid PrecipitationAcid Precipitation– Coal-burning power plants in the midwestern United States release large amounts Coal-burning power plants in the midwestern United States release large amounts

of sulfur dioxide because the coal they burn contains high amounts of sulfur.of sulfur dioxide because the coal they burn contains high amounts of sulfur.

– When acids are carried into wet weather, they become part of the rain, When acids are carried into wet weather, they become part of the rain, snow, or fog that falls to the ground in areas far from their source. snow, or fog that falls to the ground in areas far from their source.

Reducing Air PollutionReducing Air Pollution Solving air pollution problems requires Solving air pollution problems requires

cooperation between multiple governments cooperation between multiple governments because pollution travels across borders.because pollution travels across borders.

– There has been an international effort to reduce There has been an international effort to reduce global air pollution caused by carbon dioxide and global air pollution caused by carbon dioxide and CFCs. CFCs.

– In the United States, the 1990 Clean Air Act set In the United States, the 1990 Clean Air Act set specific reduction goals and enforcement specific reduction goals and enforcement policies for many types of air pollution. policies for many types of air pollution.

Reducing Air PollutionReducing Air PollutionThe Clean Air Act The Clean Air Act of 1972 was an of 1972 was an attempt to reduce attempt to reduce the amount of air the amount of air pollution in the pollution in the United States. United States. This graph tracks This graph tracks the emission rates the emission rates of six major air of six major air pollutants over a pollutants over a 30-year period.30-year period.

Reducing Air PollutionReducing Air Pollution Many coal-burning power plants have installed a Many coal-burning power plants have installed a

device such as the wet scrubber to reduce emissions device such as the wet scrubber to reduce emissions

of particulate matter and sulfur dioxide.of particulate matter and sulfur dioxide.

Reducing Air PollutionReducing Air Pollution Removing older, highly polluting vehicles from Removing older, highly polluting vehicles from

roadways is the most effective way to reduce roadways is the most effective way to reduce air pollution.air pollution.

– It is estimated that just 10 percent of the motor It is estimated that just 10 percent of the motor vehicles in operation produce 50 to 60 percent of vehicles in operation produce 50 to 60 percent of the air pollution generated by gasoline-powered the air pollution generated by gasoline-powered engines.engines.

Human Impact on Water Human Impact on Water ResourcesResources

In 1995, the United States consumed 378 billion L In 1995, the United States consumed 378 billion L of water per day. of water per day.

Freshwater use has nearly doubled since 1960 Freshwater use has nearly doubled since 1960 and the demand is expected to continue to and the demand is expected to continue to increase. increase.

When water supplies are limited, conflicts occur When water supplies are limited, conflicts occur between the needs of people and the needs of between the needs of people and the needs of other users, including wildlife.other users, including wildlife.

Human Impact on Water Human Impact on Water ResourcesResources

This graph This graph illustrates the illustrates the percentage of total percentage of total water supplies water supplies used for various used for various purposes in the purposes in the United States.United States.

Water PollutionWater Pollution

Water-pollution sources are grouped into two Water-pollution sources are grouped into two main types. main types.

– Point sourcesPoint sources generate pollution from a generate pollution from a single point of origin, such as a sewage-single point of origin, such as a sewage-treatment plant or an industrial site.treatment plant or an industrial site.

– Nonpoint sourcesNonpoint sources generate pollution from generate pollution from widely spread areas.widely spread areas.


Point SourcesPoint Sources– Common point sources of water pollution include:Common point sources of water pollution include:

Bacteria and viruses that enter water systems through improper disposal of sewage.Bacteria and viruses that enter water systems through improper disposal of sewage. Toxic wastes that enter streams from both illegal dumping and accidental spills. Toxic wastes that enter streams from both illegal dumping and accidental spills.


Nonpoint SourcesNonpoint Sources– Common nonpoint sources of water pollution Common nonpoint sources of water pollution

include:include: Rainwater that has absorbed air pollutants or has become acidic.Rainwater that has absorbed air pollutants or has become acidic. Dissolved pesticides and fertilizers from farms Dissolved pesticides and fertilizers from farms

and lawns.and lawns.

Runoff from roads and parking lots that includes oil, gasoline, and other chemicalsRunoff from roads and parking lots that includes oil, gasoline, and other chemicals..


Pollution of GroundwaterPollution of Groundwater– A wide variety of pollutants can seep into the ground and foul underground water supplies. A wide variety of pollutants can seep into the ground and foul underground water supplies.

– Once groundwater is contaminated, the pollutants can be very difficult to remove.Once groundwater is contaminated, the pollutants can be very difficult to remove.


Pollution in the OceansPollution in the Oceans– Since nearly 50 percent of the U.S. population lives near coastlines, pollutants from cities often end up in estuaries and other near-shore regions.Since nearly 50 percent of the U.S. population lives near coastlines, pollutants from cities often end up in estuaries and other near-shore regions.

– Sewage water is a major source of near-shore pollution around coastal areas due to high levels of nitrogen and phosphorus that can create blooms of Sewage water is a major source of near-shore pollution around coastal areas due to high levels of nitrogen and phosphorus that can create blooms of cyanobacteria.cyanobacteria.

– Untreated sewage, sometimes disposed of by pumping it through pipelines that extend far out into the ocean, can create large dead zones on the ocean floor Untreated sewage, sometimes disposed of by pumping it through pipelines that extend far out into the ocean, can create large dead zones on the ocean floor where there are no living organisms. where there are no living organisms.

Reducing Water Reducing Water PollutionPollution

Two major laws have been passed in the Two major laws have been passed in the United States to combat water pollution: United States to combat water pollution:

– The Safe Drinking Water Act of 1974 was The Safe Drinking Water Act of 1974 was designed to ensure that everyone in the United designed to ensure that everyone in the United States has access to safe drinking water. States has access to safe drinking water.

– The Clean Water Act of 1972, the primary The Clean Water Act of 1972, the primary federal law that protects our nation’s waters, federal law that protects our nation’s waters, was created to eliminate discharge of pollutants was created to eliminate discharge of pollutants into waterways, lakes, and wetlands, and to into waterways, lakes, and wetlands, and to restore water quality to levels that allow for restore water quality to levels that allow for recreational uses of waters.recreational uses of waters.

– Two-thirds of the nation’s waters are now safe Two-thirds of the nation’s waters are now safe for recreation, compared to only one-third in for recreation, compared to only one-third in 1972. 1972.

Water ConservationWater Conservation Water conservation, versus developing new Water conservation, versus developing new

supplies, is the most common solution to excessive supplies, is the most common solution to excessive demand.demand.

– Utilizing efficient irrigation methods reduces Utilizing efficient irrigation methods reduces water usage. water usage.

– Industries can develop ways to recycle cooling Industries can develop ways to recycle cooling water and wastewater. water and wastewater.

– Manufacturing processes often can use Manufacturing processes often can use recycled water, or be redesigned to conserve recycled water, or be redesigned to conserve water.water.

– Charging for public water that households use Charging for public water that households use encourages people to fix leaks and conserve encourages people to fix leaks and conserve water.water.