chapter 55 conservation biology and restoration ecology

Chapter 55Chapter 55

Conservation Biology and Restoration Ecology

The Biodiversity Crisis• Conservation biology integrates the following fields

to conserve biological diversity at all levels

– Ecology

– Evolutionary biology

– Physiology

– Molecular biology

– Genetics

– Behavioral ecology

• Restoration ecology applies ecological principles

– in an effort to return degraded ecosystems to conditions as similar as possible to their natural state

• Tropical forests

– contain some of the greatest concentrations of species

– are being destroyed at an alarming rate

Figure 55.1

• Throughout the biosphere, human activities

– are altering ecosystem processes on which we and other species depend

• Concept 55.1: Human activities threaten Earth’s biodiversity

• Rates of species extinction

– are difficult to determine under natural conditions because of immigration/emigration.

• The current rate of species extinction is high

– and is largely a result of ecosystem degradation by humans

• Humans are threatening Earth’s biodiversity Due to human activity.

The Three Levels of Biodiversity• Biodiversity has three main components

– Genetic diversity

– Species diversity

– Ecosystem diversity Genetic diversity in a vole population

Species diversity in a coastal redwood ecosystem

Community and ecosystem diversityacross the landscape of an entire regionFigure 55.2

Genetic Diversity

• Genetic diversity comprises

– the genetic variation within a population

– the genetic variation between populations

Genetics create a variation of species in a population. This may help you adapt to certain conditions. Disease resistance is also due to genetic variation.

Species Diversity

• Species diversity

– is the variety of species in an ecosystem or throughout the biosphere

• An endangered species

– is one that is in danger of becoming extinct throughout its range. This species is a species in danger of becoming extinct.

• Threatened species

– are those that are considered likely to become endangered in the foreseeable future

• Conservation biologists are concerned about species loss

– because of a number of alarming statistics regarding extinction and biodiversity

• Harvard biologist E. O. Wilson has identified the Hundred Heartbeat Club

– species that number fewer than 100 individuals and are only that many heartbeats from extinction (a) Philippine eagle

(b) Chinese river dolphin

(c) Javan rhinocerosFigure 55.3a–c

12% of known 10,000 bird species & 24% of 5,000 known species of mammals are going extinct.

Ecosystem Diversity

• Ecosystem diversity

– identifies the variety of ecosystems in the biosphere

– is being affected by human activity

Biodiversity and Human Welfare

• Human biophilia

– allows us to recognize the value of biodiversity for its own sake

– This is our connection to nature. This is something within us that wants us to care and appreciate nature.

• Species diversity

– brings humans many practical benefits

Benefits of Species and Genetic Diversity

• Many pharmaceuticals

– contain substances originally derived from plants. Rosey Periwinkle. This plant contains alkaloids.

Figure 55.4

now 25% of all tropical plants may be gone in next 30 years14% of vascular plants endangered

• The loss of species

– also means the loss of genes and genetic diversity

• The enormous genetic diversity of organisms on Earth

– has the potential for great human benefit

• Biodiversity is crucial natural resource, & species that are threatened could provide crops, fibers, & medicines for human use

• Of top 150 drugs in U.S., 118 based on natural sources: 74% on plants, 18% on fungi,5% on bacteria, 3% on one vertebrate (snake) venom

• 80% human population depends on traditional medicine; 85% of traditional medicine involves use of plant extracts

• Human history have used 7,000 plant species for food

– but, 70,000 plants have edible parts

– currently 82 plant species contribute to 90% of food plants

– about 15 species provide bulk of calories consumed by humans

– Does this leave us vulnerable?

– What if there is a change in climate?

• Last ice age (about 20,000 years ago) much of Europe and N. America covered by mile-thick ice

• Global climate has been relatively stable since agriculture was invented about 10,000 years ago

– life has played a role in buffering climate change

– How?

• ecosystems can help prevent overheating of Earth by removing greenhouse CO2 from atmosphere

The decomposers• 130 billion tons of waste processed each year

• 30% from human activities

• Conversion of complex organic molecules to simple one

• includes industrial wastes like detergents, pesticides, oil, acids, paper

• Soils return simple inorganic molecules to plants as nutrients

• depends on activity of bacteria, fungi, algae, worms, crustaceans, insects

• bacteria fix nitrogen, fungi make nutrients available, worms are mechanical blenders

• Under square metre of pasture soil is inhabited by 50,000 earthworms, 50,000 insects & mites, 12 million roundworms

• What about soil microorganisms?

– teaspoon of soil contains about 30,000 protozoa, 500,000 algae, 400,000 fungi, billions of individual bacteria

– They don’t need us but we need them

Ecosystem Services

• Ecosystem services encompass all the processes

– through which natural ecosystems and the species they contain help sustain human life on Earth

• Ecosystem services include

– Purification of air and water

– Detoxification and decomposition of wastes

– Cycling of nutrients

– Moderation of weather extremes

– And many others

Four Major Threats to Biodiversity

• Most species loss can be traced to four major threats

– Habitat destruction

– Introduced species

– Overexploitation

– Disruption of “interaction networks”

Habitat Destruction

• Human alteration of habitat

– is the single greatest threat to biodiversity throughout the biosphere

• Massive destruction of habitat

– has been brought about by many types of human activity. Like:

– Clear cutting

– Population

– Mining… agriculture

• Many natural landscapes have been broken up

– fragmenting habitat into small patches… Could be natural or manmade.

Figure 55.5

• In almost all cases

– habitat fragmentation and destruction leads to loss of biodiversity

Introduced Species

• Introduced species

– are those that humans move from the species’ native locations to new geographic regions

• Introduced species that gain a foothold in a new habitat

– usually disrupt their adopted community

(a) Brown tree snake, intro- duced to Guam in cargo

(b) Introduced kudzu thriving in South CarolinaFigure 55.6a, b

Overexploitation

• Overexploitation refers generally to the human harvesting of wild plants or animals.

– at rates exceeding the ability of populations of those species to rebound (hunting animals, logging for furniture)

• The fishing industry

– has caused significant reduction in populations of certain game fish, codfish.

Figure 55.7

Disruption of Interaction Networks

• The extermination of keystone species by humans

– can lead to major changes in the structure of communities. This bat is a keystone species because its lack of presence has resulted in a decrease of plants, due to lack of pollination.

Figure 55.8

• Concept 55.2: 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

Small-Population Approach

• Conservation biologists who adopt the small-population approach

– study the processes that can cause very small populations finally to become extinct

The Extinction Vortex

• A small population is prone to positive-feedback loops

– that draw the population down an extinction vortex

Smallpopulation

InbreedingGenetic

drift

Lower reproduction

Higher mortality

Loss ofgenetic

variabilityReduction inindividual

fitness andpopulationadaptability

Smallerpopulation

Figure 55.9

• The key factor driving the extinction vortex

– is the loss of the genetic variation necessary to enable evolutionary responses to environmental change

Case Study: The Greater Prairie Chicken and the Extinction Vortex

• Populations of the greater prairie chicken

– were fragmented by agriculture and later found to exhibit decreased fertility

• As a test of the extinction vortex hypothesis

– scientists imported genetic variation by transplanting birds from larger populations

• The declining population rebounded

– confirming that it had been on its way down an extinction vortex

EXPRIMENT Researchers observed that the population collapse of the greater prairie chicken was mirrored in a reduction in fertility, as measured by the hatching rate of eggs. Comparison of DNA samples from the Jasper County, Illinois, population with DNA from feathers in museum specimens showed that genetic variation had declined in the study population. In 1992, researchers began experimental translocations of prairie chickens from Minnesota, Kansas, and Nebraska in an attempt to increase genetic variation.

RESULTS After translocation (blue arrow), the viability of eggs rapidly improved, and the population rebounded.

CONCLUSION The researchers concluded that lack of genetic variation had started the Jasper County population of prairie chickens down the extinction vortex.

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Figure 55.10

Minimum Viable Population Size

• The minimum viable population (MVP)

– is the minimum population size at which a species is able to sustain its numbers and survive

• A population viability analysis (PVA)

– predicts a population’s chances for survival over a particular time

– factors in the MVP of a population

Effective Population Size

• A meaningful estimate of MVP

– requires a researcher to determine the effective population size, which is based on the breeding size of a population

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

Figure 55.11

• This study has shown that the grizzly bear population

– has grown substantially in the past 20 yearsN

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Females with cubs

Cubs

YearFigure 55.12

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 in the first place

Steps for Analysis and Intervention

• The declining-population approach

– requires that population declines be evaluated on a case-by-case basis

– involves a step-by-step proactive conservation strategy

Case Study: Decline of the Red-Cockaded Woodpecker

• Red-cockaded woodpeckers

– require specific habitat factors for survival

– had been forced into decline by habitat destruction

(a) A red-cockaded woodpecker perches at the entrance to its nest site in a longleaf pine.

(b) Forest that can sustain red-cockaded woodpeckers has low undergrowth.

(c) Forest that cannot sustain red-cockaded woodpeckers has high, dense undergrowth that impacts the woodpeckers’ access to feeding grounds.Figure 55.13a–c

• In a study where breeding cavities were constructed

– new breeding groups formed only in these sites

• On the basis of this experiment

– a combination of habitat maintenance and excavation of new breeding cavities has enabled a once-endangered species to rebound

Weighing Conflicting Demands

• Conserving species often requires resolving conflicts

– between the habitat needs of endangered species and human demands

• Concept 55.3: Landscape and regional conservation aim to sustain entire biotas

• In recent years, conservation biology

– has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes

• One goal of landscape ecology, of which ecosystem management is part

– is to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planning

Landscape Structure and Biodiversity

• The structure of a landscape

– can strongly influence biodiversity

Fragmentation and Edges

• The boundaries, or edges, between ecosystems

– are defining features of landscapes

(a) Natural edges. Grasslands give way to forest ecosystems in Yellowstone National Park.

(b) Edges created by human activity. Pronounced edges (roads) surround clear-cuts in this photograph of a heavily logged rain forest in Malaysia.Figure 55.14a, b

• As habitat fragmentation increases

– and edges become more extensive, biodiversity tends to decrease

• Research on fragmented forests has led to the discovery of two groups of species

– those that live in forest edge habitats and those that live in the forest interior

Figure 55.15

Corridors That Connect Habitat Fragments

• A movement corridor

– is a narrow strip of quality habitat connecting otherwise isolated patches

• In areas of heavy human use

– artificial corridors are sometimes constructed

Figure 55.16

• Movement corridors

– promote dispersal and help sustain populations

Establishing Protected Areas

• Conservation biologists are applying their understanding of ecological dynamics

– in establishing protected areas to slow the loss of biodiversity

• Much of the focus on establishing protected areas

– has been on hot spots of biological diversity

Finding Biodiversity Hot Spots

• A biodiversity hot spot is a relatively small area

– with an exceptional concentration of endemic species and a large number of endangered and threatened species

Terrestrial biodiversity hot spots

Equator

Figure 55.17

• Biodiversity hot spots are obviously good choices for nature reserves

– but identifying them is not always easy

Philosophy of Nature Reserves

• Nature reserves are biodiversity islands

– in a sea of habitat degraded to varying degrees by human activity

• One argument for extensive reserves

– is that large, far-ranging animals with low-density populations require extensive habitats

• In some cases

– the size of reserves is smaller than the actual area needed to sustain a population

Biotic boundary forshort-term survival;MVP is 50 individuals.

Biotic boundary forlong-term survival;MVP is 500 individuals.

Grand TetonNational Park

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Yellowstone National Park

Shoshone R.

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Yellowstone R.

Figure 55.18

Zoned Reserves

• The zoned reserve model recognizes that conservation efforts

– often involve working in landscapes that are largely human dominated

• Zoned reserves

– are often established as “conservation areas”

(a) Boundaries of the zoned reserves are indicated by black outlines.

(b) Local schoolchildren marvel at the diversity of life in one of Costa Rica’s reserves.

Nicaragua

CostaRica

Pan

amaNational park land

Buffer zone

PACIFIC OCEAN

CARIBBEAN SEA

Figure 55.19a, b

• Some zoned reserves in the Fiji islands are closed to fishing

– which actually helps to improve fishing success in nearby areas

Figure 55.20

• Concept 55.4: Restoration ecology attempts to restore degraded ecosystems to a more natural state

• The larger the area disturbed

– the longer the time that is required for recovery

• Whether a disturbance is natural or caused by humans

– seems to make little difference in this size-time relationship

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Natural disasters

Human-caused disasters

Natural OR human-caused disasters

Meteorstrike

Groundwaterexploitation

Industrialpollution

Urbanization Salination

Modernagriculture Flood

Volcaniceruption

Acidrain

Forestfire

Nuclearbomb

Tsunami

Oilspill

Slash& burn

Land-slide

Treefall

Lightningstrike

Spatial scale (km2)(log scale)

Figure 55.21

• One of the basic assumptions of restoration ecology

– is that most environmental damage is reversible

• Two key strategies in restoration ecology

– are bioremediation and augmentation of ecosystem processes

Bioremediation

• Bioremediation

– is the use of living organisms to detoxify ecosystems

Biological Augmentation

• Biological augmentation

– uses organisms to add essential materials to a degraded ecosystem

Exploring Restoration

• The newness and complexity of restoration ecology

– require scientists to consider alternative solutions and adjust approaches based on experience

• Concept 55.5: Sustainable development seeks to improve the human condition while conserving biodiversity

• Facing increasing loss and fragmentation of habitats

– How can we best manage Earth’s resources?

Sustainable Biosphere Initiative

• The goal of this initiative is to define and acquire the basic ecological information necessary

– for the intelligent and responsible development, management, and conservation of Earth’s resources

Case Study: Sustainable Development in Costa Rica

• Costa Rica’s success in conserving tropical biodiversity

– has involved partnerships between the government, other organizations, and private citizens

• Human living conditions in Costa Rica

– have improved along with ecological conservationIn

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Figure 55.23

Biophilia and the Future of the Biosphere

• Our modern lives

– are very different from those of early humans who hunted and gathered and painted on cave walls

(a) Detail of animals in a Paleolithic mural, Lascaux, FranceFigure 55.24a

• But our behavior

– reflects remnants of our ancestral attachment to nature and the diversity of life, the concept of biophilia

(b) Biologist Carlos Rivera Gonzales examining a tiny tree frog in PeruFigure 55.24b

• Our innate sense of connection to nature

– may eventually motivate a realignment of our environmental priorities