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Global Ecology and Conservation Biology
43 Global Ecology and Conservation Biology
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Overview: Psychedelic Treasure
Scientists have named and described 1.8 million species Biologists estimate 10–100 million species exist on Earth Tropical forests contain some of the greatest concentrations of species and are being destroyed at an alarming rate Humans are rapidly pushing many species, including the newly discovered psychedelic rock gecko, toward extinction 2
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Figure 43.1 Figure 43.1 What will be the fate of this newly described lizard species? 3
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Figure 43.2 Figure 43.2 Tropical deforestation in Vietnam 4
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Conservation biology, which seeks to preserve life, integrates several fields
Ecology Evolutionary biology Molecular biology Genetics Physiology 5
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Concept 43.1: Human activities threaten Earth’s biodiversity
Rates of species extinction are difficult to determine under natural conditions Extinction is a natural process, but the high rate of extinction is responsible for today’s biodiversity crisis Human activities are threatening Earth’s biodiversity 6
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Three Levels of Biodiversity
Biodiversity has three main components Genetic diversity Species diversity Ecosystem diversity 7
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Genetic diversity in a vole population
Figure Genetic diversity in a vole population Figure Three levels of biodiversity (step 1) 8
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Genetic diversity in a vole population
Figure Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Figure Three levels of biodiversity (step 2) 9
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Genetic diversity in a vole population
Figure Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Figure Three levels of biodiversity (step 3) Community and ecosystem diversity across the landscape of an entire region 10
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Genetic Diversity Genetic diversity comprises genetic variation within a population and between populations Population extinctions reduce genetic diversity, which in turn reduces the adaptive potential of a species 11
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Species Diversity Species diversity is the variety of species in an ecosystem or throughout the biosphere According to the U.S. Endangered Species Act An endangered species is “in danger of becoming extinct throughout all or a significant portion of its range” A threatened species is likely to become endangered in the near future 12
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Extinction may be local or global
Conservation biologists are concerned about species loss because of alarming statistics regarding extinction and biodiversity Globally, 12% of birds and 21% of mammals are threatened with extinction Extinction may be local or global 13
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Philippine eagle Yangtze River dolphin Figure 43.4
Figure 43.4 A hundred heartbeats from extinction 14
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Philippine eagle Figure 43.4a
Figure 43.4a A hundred heartbeats from extinction (part 1: Philippine eagle) Philippine eagle 15
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Yangtze River dolphin Figure 43.4b
Figure 43.4b A hundred heartbeats from extinction (part 2: Yangtze River dolphin) Yangtze River dolphin 16
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Ecosystem Diversity Human activity is reducing ecosystem diversity, the variety of ecosystems in the biosphere More than 50% of wetlands in the contiguous United States have been drained and converted to agricultural or other use 17
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The local extinction of one species can have a negative impact on other species in an ecosystem
For example, flying foxes (bats) are important pollinators and seed dispersers in the Pacific Islands 18
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Figure 43.5 Figure 43.5 The endangered Marianas “flying fox” bat (Pteropus mariannus), an important pollinator 19
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Biodiversity and Human Welfare
Human biophilia allows us to recognize the value of biodiversity for its own sake Species diversity brings humans practical benefits 20
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Benefits of Species and Genetic Diversity
Species related to agricultural crops can have important genetic qualities For example, plant breeders bred virus-resistant commercial rice by crossing it with a wild population In the United States, 25% of prescriptions contain substances originally derived from plants For example, the rosy periwinkle contains alkaloids that inhibit cancer growth 21
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Rosy periwinkle Figure 43.UN01
Figure 43.UN01 In-text figure, rosy periwinkle, p. 885 Rosy periwinkle 22
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The loss of species also means loss of unique genes and genetic diversity
The enormous genetic diversity of organisms has potential for great human benefit 23
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Ecosystem Services Ecosystem services encompass all the processes through which natural ecosystems help sustain human life Some examples of ecosystem services Purification of air and water Detoxification and decomposition of wastes Crop pollination, pest control, and soil preservation Ecosystem services have an estimated value of $33 trillion per year, but are provided for free 24
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Threats to Biodiversity
Most species loss can be traced to four major threats Habitat loss Introduced species Overharvesting Global change 25
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Habitat Loss Human alteration of habitat is the greatest threat to biodiversity throughout the biosphere In almost all cases, habitat fragmentation and destruction lead to loss of biodiversity For example In Wisconsin, prairie habitat has been reduced by over 99.9%, resulting in the loss of up to 60% of the original plant species 26
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Figure 43.6 Figure 43.6 Habitat fragmentation in the foothills of Los Angeles 27
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Introduced Species Introduced species are those that humans move from native locations to new geographic regions Without their native predators, parasites, and pathogens, introduced species may spread rapidly Introduced species that gain a foothold in a new habitat usually disrupt their adopted community 28
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Humans have deliberately introduced some species with good intentions but disastrous effects
For example, kudzu was intentionally introduced to the southern United States 29
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Figure 43.7 Figure 43.7 Kudzu, an introduced species, thriving in South Carolina 30
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Overharvesting Overharvesting is human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound Species with restricted habitats or large body size with low reproductive rates are especially vulnerable to overharvesting For example, elephant populations declined because of harvesting for ivory 31
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DNA analysis can help conservation biologists identify the source of illegally obtained animal products For example, DNA from illegally harvested ivory can be used to trace the original population of elephants to within a few hundred kilometers 32
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Figure 43.8 Figure 43.8 Ecological forensics and elephant poaching 33
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Overfishing has decimated wild fish populations
For example, the North Atlantic bluefin tuna population decreased by 80% in ten years 34
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Figure 43.9 Figure 43.9 Overharvesting 35
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Global Change Global change includes alterations in climate, atmospheric chemistry, and broad ecological systems Acid precipitation is rain, snow, sleet, or fog with a pH 5.2 Acid precipitation contains sulfuric acid and nitric acid from the burning of wood and fossil fuels 36
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Acid precipitation kills fish and other lake-dwelling organisms
Air pollution from one region can result in acid precipitation downwind For example, industrial pollution in the midwestern United States caused acid precipitation in eastern Canada in the 1960s Acid precipitation kills fish and other lake-dwelling organisms Environmental regulations have helped to decrease acid precipitation For example, sulfur dioxide emissions in the United States decreased 40% between 1993 and 2009 37
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Figure 43.10 4.8 4.7 4.6 4.5 4.4 pH 4.3 4.2 Figure Changes in the pH of precipitation at Hubbard Brook, New Hampshire 4.1 4.0 1960 ’65 ’70 ’75 ’80 ’85 ’90 ’95 2000 ’05 ’10 Year 38
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Concept 43.2: Population conservation focuses on population size, genetic diversity, and critical habitat Biologists focusing on conservation at the population and species levels follow two main approaches The small-population approach The declining-population approach 39
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Small-Population Approach
The small-population approach studies processes that can make small populations become extinct 40
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The Extinction Vortex: Evolutionary Implications of Small Population Size
A small population is prone to inbreeding and genetic drift, which draw it down an extinction vortex The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change Small populations and low genetic diversity do not always lead to extinction 41
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Inbreeding, genetic drift
Figure 43.11 Small population Inbreeding, genetic drift Lower reproduction, higher mortality Loss of genetic variability Figure Processes driving an extinction vortex Lower individual fitness and population adaptability Smaller population 42
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Case Study: The Greater Prairie Chicken and the Extinction Vortex
Populations of the greater prairie chicken in North America were fragmented by agriculture and later found to exhibit decreased fertility To test the extinction vortex hypothesis, scientists imported genetic variation by transplanting birds from larger populations The declining population rebounded, confirming that low genetic variation had been causing an extinction vortex 43
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(a) Population dynamics
Figure 43.12 Results 200 150 Number of male birds 100 Translocation 50 1970 1975 1980 1985 1990 1995 Year (a) Population dynamics 100 Figure Inquiry: What caused the drastic decline of the Illinois greater prairie chicken population? 90 80 70 Eggs hatched (%) 60 50 40 30 1970–’74 ’75–’79 ’80–’84 ’85–’89 ’90 ’93–’97 Years (b) Hatching rate 44
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(a) Population dynamics
Figure 43.12a Results 200 150 100 Number of male birds Translocation 50 Figure 43.12a Inquiry: What caused the drastic decline of the Illinois greater prairie chicken population? (part 1: population dynamics) 1970 1975 1980 1985 1990 1995 Year (a) Population dynamics 45
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Results 100 90 80 Eggs hatched (%) 70 60 50 40 30 Years
Figure 43.12b Results 100 90 80 70 60 Eggs hatched (%) 50 40 30 Figure 43.12b Inquiry: What caused the drastic decline of the Illinois greater prairie chicken population? (part 2: hatching rate) 1970–’74 ’75–’79 ’80–’84 ’85–’89 ’90 ’93–’97 Years (b) Hatching rate 46
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Figure 43.12c Figure 43.12c Inquiry: What caused the drastic decline of the Illinois greater prairie chicken population? (part 3: photo) 47
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Minimum Viable Population Size
Minimum viable population (MVP) is the minimum population size at which a species can survive The MVP depends on factors that affect a population’s chances for survival over a particular time 48
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Effective Population Size
A meaningful estimate of MVP requires determining the effective population size, which is based on the population’s breeding potential
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Ne = Nf + Nm Effective population size (Ne) is estimated by 4Nf Nm
where Nf and Nm are the number of females and the number of males, respectively, that breed successfully Conservation programs attempt to sustain population sizes including a minimum number of reproductively active individuals to retain genetic diversity 4Nf Nm Nf + Nm Ne =
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Case Study: Analysis of Grizzly Bear Populations
One of the first population viability analyses was conducted as part of a long-term study of grizzly bears in Yellowstone National Park It is estimated that a population of 100 bears would have a 95% chance of surviving about 200 years The Yellowstone grizzly population is estimated to include about 500 individuals, but the Ne is about 125
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Figure 43.13 Figure Long-term monitoring of a grizzly bear population 52
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The Yellowstone grizzly population has low genetic variability compared with other grizzly populations Introducing individuals from other populations would increase the numbers and genetic variation Promoting dispersal between fragmented populations is an urgent conservation need
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Declining-Population Approach
The declining-population approach Focuses on threatened and endangered populations that show a downward trend, regardless of population size Emphasizes the environmental factors that caused a population to decline
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Case Study: Decline of the Red-Cockaded Woodpecker
Red-cockaded woodpeckers require living trees in mature pine forests These woodpeckers require forests with little undergrowth Logging, agriculture, and fire suppression have reduced suitable habitat
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Red-cockaded woodpecker
Figure 43.14 Red-cockaded woodpecker Figure A habitat requirement of the red-cockaded woodpecker (a) Forests with low undergrowth (b) Forests with high, dense undergrowth 56
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(a) Forests with low undergrowth
Figure 43.14a Figure 43.14a A habitat requirement of the red-cockaded woodpecker (part 1: low undergrowth) (a) Forests with low undergrowth 57
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(b) Forests with high, dense undergrowth
Figure 43.14b Figure 43.14b A habitat requirement of the red-cockaded woodpecker (part 2: high undergrowth) (b) Forests with high, dense undergrowth 58
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Red-cockaded woodpecker
Figure 43.14c Figure 43.14c A habitat requirement of the red-cockaded woodpecker (part 3: woodpecker) Red-cockaded woodpecker 59
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Red-cockaded woodpeckers take months to excavate nesting cavities
In a study where breeding cavities were constructed in restored sites, new breeding groups formed only in sites with constructed cavities Based on this experiment, a combination of habitat maintenance and excavation of breeding cavities enabled this endangered species to rebound
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Weighing Conflicting Demands
Conserving species often requires resolving conflicts between habitat needs of endangered species and human demands For example, in the western United States, habitat preservation for many species is at odds with grazing and resource extraction industries The ecological role of the target species is an important consideration in conservation
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Concept 43.3: Landscape and regional conservation help sustain biodiversity
Conservation biology has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes Ecosystem management is part of landscape ecology, which seeks to make biodiversity conservation part of land-use planning
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Landscape Structure and Biodiversity
The structure of a landscape can strongly influence biodiversity
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Fragmentation and Edges
The boundaries, or edges, between ecosystems are defining features of landscapes Some species take advantage of edge communities to access resources from both adjacent areas
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Figure 43.15 Figure Edges between ecosystems 65
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The Biological Dynamics of Forest Fragments Project in the Amazon examines the effects of fragmentation on biodiversity Landscapes dominated by fragmented habitats support fewer species due to a loss of species adapted to habitat interiors
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Figure 43.16 Figure Amazon rain forest fragments created as part of the Biological Dynamics of Forest Fragments Project 67
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Corridors That Connect Habitat Fragments
A movement corridor is a narrow strip of habitat connecting otherwise isolated patches Movement corridors promote dispersal and reduce inbreeding Corridors can also have harmful effects, for example, promoting the spread of disease In areas of heavy human use, artificial corridors are sometimes constructed
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Figure 43.17 Figure An artificial corridor 69
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Establishing Protected Areas
Conservation biologists apply understanding of landscape dynamics in establishing protected areas to slow the loss of biodiversity
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Preserving Biodiversity Hot Spots
A biodiversity hot spot is a relatively small area with a great concentration of endemic species and many endangered and threatened species Biodiversity hot spots are good choices for nature reserves, but identifying them is not always easy
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Designation of hot spots is often biased toward saving vertebrates and plants
Hot spots can change with climate change
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Earth’s terrestrial ( ) and marine ( ) biodiversity hot spots
Figure 43.18 Equator Figure Earth’s terrestrial and marine biodiversity hot spots Earth’s terrestrial ( ) and marine ( ) biodiversity hot spots 73
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Philosophy of Nature Reserves
Nature reserves are biodiversity islands in a sea of habitat degraded by human activity Nature reserves must consider disturbances as a functional component of all ecosystems
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An important question is whether to create numerous small reserves or fewer large reserves
Smaller reserves may be more realistic and may slow the spread of disease between populations One argument for large reserves is that large, far-ranging animals with low-density populations require extensive habitats Large reserves also have proportionally smaller perimeters, reducing edge effects
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Grand Teton National Park
Figure 43.19 50 100 Kilometers MONTANA WYOMING Yellowstone MONTANA National Park IDAHO Figure Biotic boundaries for grizzly bears in Yellowstone and Grand Teton National Parks Grand Teton National Park Snake R. Biotic boundary for short-term survival; MVP is 50 individuals. WYOMING Biotic boundary for long-term survival; MVP is 500 individuals. IDAHO 76
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Zoned Reserves A zoned reserve includes relatively undisturbed areas surrounded by human-modified areas of economic value The zoned reserve approach creates buffer zones by regulating human activities in areas surrounding the protected core Zoned reserves are often established as “conservation areas” Costa Rica has become a world leader in establishing zoned reserves
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Nicaragua CARIBBEAN SEA Costa Rica National park land Buffer zone
Figure 43.20 Nicaragua CARIBBEAN SEA Costa Rica National park land Figure Zoned reserves in Costa Rica Buffer zone PACIFIC OCEAN 78
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Many fish populations have collapsed due to modern fishing practices
Some areas in the Fiji islands are closed to fishing, which improves fishing success in nearby areas The United States has adopted a similar zoned reserve system with the Florida Keys National Marine Sanctuary Video: Coral Reef
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Florida Keys National Marine Sanctuary
Figure 43.21 GULF OF MEXICO FLORIDA Florida Keys National Marine Sanctuary 50 km Figure A diver measuring coral in the Florida Keys National Marine Sanctuary 80
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Figure 43.21a Figure 43.21a A diver measuring coral in the Florida Keys National Marine Sanctuary (photo) 81
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Concept 43.4: Earth is changing rapidly as a result of human actions
The locations of reserves today may be unsuitable for their species in the future Human-caused changes in the environment include Nutrient enrichment Accumulation of toxins Climate change
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Nutrient Enrichment Humans transport nutrients from one part of the biosphere to another Harvest of agricultural crops exports nutrients from the agricultural ecosystem Agriculture leads to the depletion of nutrients in the soil Fertilizers add nitrogen and other nutrients to the agricultural ecosystem
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Critical load is the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity Nutrients that exceed the critical load leach into groundwater or run off into aquatic ecosystems Agricultural runoff and sewage lead to phytoplankton blooms in the Atlantic Ocean Decomposition of phytoplankton blooms causes “dead zones” due to low oxygen levels
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Figure 43.22 Figure A phytoplankton bloom arising from nitrogen pollution in the Mississippi basin that leads to a dead zone 85
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Toxins in the Environment
Humans release many toxic chemicals, including synthetics previously unknown to nature In some cases, harmful substances persist for long periods in an ecosystem One reason toxins are harmful is that they become more concentrated in successive trophic levels Biological magnification concentrates toxins at higher trophic levels, where biomass is lower
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PCBs and many pesticides such as DDT are subject to biological magnification in ecosystems
Herring gulls of the Great Lakes lay eggs with PCB levels 5,000 times greater than in phytoplankton
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Herring gull eggs 124 ppm Lake trout 4.83 ppm Concentration of PCBs
Figure 43.23 Herring gull eggs 124 ppm Lake trout 4.83 ppm Concentration of PCBs Smelt 1.04 ppm Figure Biological magnification of PCBs in a Great Lakes food web Zooplankton ppm Phytoplankton ppm 88
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In the 1960s Rachel Carson brought attention to the biomagnification of DDT in birds in her book Silent Spring DDT was banned in the United States in 1971 Countries with malaria face a trade-off between killing mosquitoes (malarial vectors) and protecting other species
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Figure 43.24 Figure Rachel Carson 90
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Pharmaceutical drugs enter freshwater ecosystems through human and animal waste
Estrogen used in birth control pills can cause feminization of males in some species of fish
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Sewage treatment plant Lakes and rivers
Figure 43.25 Pharmaceuticals Farm animals Humans Toilet Manure Agricultural runoff Sludge Farms Treated effluent Figure Sources and movements of pharmaceuticals in the environment Sewage treatment plant Lakes and rivers 92
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Greenhouse Gases and Climate Change
One pressing problem caused by human activities is the rising concentration of atmospheric CO2 due to the burning of fossil fuels and deforestation
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CO2 concentration (ppm)
Figure 43.26 14.9 390 14.8 380 14.7 14.6 370 Temperature 14.5 360 14.4 CO2 concentration (ppm) 350 14.3 Average global temperature (C) 14.2 14.2 340 14.1 CO2 330 14.0 Figure Increase in atmospheric carbon dioxide concentration at Mauna Loa, Hawaii, and average global temperatures 13.9 320 13.8 310 13.7 300 13.6 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Year 94
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CO2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth; this is the greenhouse effect This effect is important for keeping Earth’s surface at a habitable temperature Increasing concentration of atmospheric CO2 is linked to increasing global temperature
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Climatologists can make inferences about prehistoric climates
CO2 levels are inferred from bubbles trapped in glacial ice Chemical isotope analysis is used to infer past temperature
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Northern coniferous forests and tundra show the strongest effects of global warming
For example, in 2007 the extent of Arctic sea ice was the smallest on record
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Range Shifts and Climate Change
Many organisms, especially plants, may not be able to disperse rapidly enough to survive rapid climate change Researchers can track changes in tree distributions since the last period of glaciation to help infer future changes due to climatic warming 98
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(b) 4.5C warming over next century
Figure 43.27 Figure Current range and predicted range for the American beech under two climate-change scenarios (a) Current range (b) 4.5C warming over next century (c) 6.5C warming over next century 99
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Climate Change Solutions
Global warming can be slowed by reducing energy needs and converting to renewable sources of energy Stabilizing CO2 emissions will require an international effort and changes in personal lifestyles and industrial processes Reduced deforestation would also decrease greenhouse gas emissions
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Concept 43.5: The human population is no longer growing exponentially but is still increasing rapidly Global environmental problems arise from growing consumption and the increasing human population No population can grow indefinitely, and humans are no exception 101
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The Global Human Population
The human population increased relatively slowly until about 1650 and then began to grow exponentially 102
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Human population (billions)
Figure 43.28 7 6 5 Human population (billions) 4 3 2 Figure Human population growth (data as of 2011) 1 8000 4000 3000 2000 1000 1000 2000 BCE BCE BCE BCE BCE CE CE 103
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The global population is now more than 7 billion
Though the global population is still growing, the rate of growth began to slow during the 1960s 104
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Annual percent increase
Figure 43.29 2.2 2.0 1.8 1.6 1.4 2011 Annual percent increase 1.2 Projected data 1.0 0.8 Figure Annual percent increase in the global human population (data as of 2011) 0.6 0.4 0.2 1950 1975 2000 2025 2050 Year 105
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The growth rates of individual nations vary with their degree of industrialization
Most of the current global population growth is concentrated in developing countries Human population growth rates can be controlled through family planning, voluntary contraception, and increased access to education for females 106
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Global Carrying Capacity
How many humans can the biosphere support? Population ecologists predict a global population of 8.110.6 billion people in 2050 107
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Estimates of Carrying Capacity
The carrying capacity of Earth for humans is uncertain The average estimate is 10–15 billion 108
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Limits on Human Population Size
The ecological footprint concept summarizes the aggregate land and water area needed to sustain the people of a nation It is one measure of how close we are to the carrying capacity of Earth Countries vary greatly in footprint size and available ecological capacity 109
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Energy use (GJ): 300 150–300 50–150 10–50 10 Figure 43.30
Figure Annual per capita energy use around the world Energy use (GJ): 300 150–300 50–150 10–50 10 110
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Our carrying capacity could potentially be limited by food, space, nonrenewable resources, or buildup of wastes Unlike other organisms, we can regulate our population growth through social changes 111
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Concept 43.6: Sustainable development can improve human lives while conserving biodiversity
The concept of sustainability helps ecologists establish long-term conservation priorities 112
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Sustainable Development
Sustainable development is development that meets the needs of people today without limiting the ability of future generations to meet their needs To sustain ecosystem processes and slow the loss of biodiversity, connections between life sciences, social sciences, economics, and humanities must be made 113
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Case Study: Sustainable Development in Costa Rica
Costa Rica’s conservation of tropical biodiversity involves partnerships between the government, nongovernmental organizations (NGOs), and private citizens Human living conditions (infant mortality, life expectancy, literacy rate) in Costa Rica have improved along with ecological conservation 114
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The Future of the Biosphere
Our lives differ greatly from those of early humans, who hunted and gathered and painted on cave walls
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(b) A 30,000-year-old ivory carving of a water bird, found in Germany
Figure 43.31 (a) Detail of animals in a 17,000-year-old cave painting, Lascaux, France (b) A 30,000-year-old ivory carving of a water bird, found in Germany Figure Biophilia, past and present (c) Nature lovers on a wildlife-watching expedition (d) A young biologist holding a songbird 116
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Figure 43.31a Figure 43.31a Biophilia, past and present (part 1: cave painting) (a) Detail of animals in a 17,000-year-old cave painting, Lascaux, France 117
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(b) A 30,000-year-old ivory carving of a water bird, found in Germany
Figure 43.31b (b) A 30,000-year-old ivory carving of a water bird, found in Germany Figure 43.31b Biophilia, past and present (part 2: ivory carving) 118
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(c) Nature lovers on a wildlife-watching expedition
Figure 43.31c Figure 43.31c Biophilia, past and present (part 3: wildlife expedition) (c) Nature lovers on a wildlife-watching expedition 119
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(d) A young biologist holding a songbird
Figure 43.31d Figure 43.31d Biophilia, past and present (part 4: study of biology) (d) A young biologist holding a songbird 120
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Our behavior reflects remnants of our ancestral attachment to nature and the diversity of life—the concept of biophilia Our sense of connection to nature may motivate realignment of our environmental priorities
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Figure 43.UN02 Figure 43.UN02 Skills exercise: graphing cyclic data 122
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Figure 43.UN03 Genetic diversity: source of variations that enable populations to adapt to environmental changes Species diversity: important in maintaining structure of communities and food webs Figure 43.UN03 Summary of key concepts: levels of biodiversity Ecosystem diversity: provides life-sustaining services such as nutrient cycling and waste decomposition 123
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