Chapter 56

Conservation Biology and Restoration Ecology

Biodiversity

The current rate of species extinction is high and is largely a result of ecosystem degradation by humans

Humans are a huge threat to Earth’s biodiversity

Levels of BiodiversityBiodiversity 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 region

Diversity

Genetic diversity comprises– The genetic variation within a population

– The genetic variation between populations

Species diversity– Is the variety of species in an ecosystem or throughout

the biosphere

Ecosystem diversity– Identifies the variety of ecosystems in the biosphere

Endangered species– Is one that is in danger of becoming extinct

throughout its range

Threatened species– Are those that are considered likely to

become endangered in the foreseeable future

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 rhinoceros

Biodiversity (affect on Human Welfare)

Biophilia: Our sense of connection to nature and to other life forms– Allows us to recognize the value of biodiversity for its

own sake

The loss of species means the loss of genes and genetic diversity

The enormous genetic diversity of organisms on Earth has the potential for great human benefit

Benefits of Species and Genetic Diversity

Many pharmaceuticals contain substances originally derived from plants

Rosy periwinkle is a source of anti-cancer drugs

Ecosystem ServicesEcosystem 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

– Pollination of crops

– Moderation of weather extremes

– Etc., etc., etc.

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 DestructionHuman alteration of habitat is the single greatest threat to biodiversity throughout the biosphere

Madagascar Deforestation

Movie

Many natural landscapes have been broken up– Fragmenting habitat into small patches

– Habitat fragmentation and destruction leads to loss of biodiversity

Fragmented forest habitat in Mount Hood National Forset

Habitat fragmentation in the foothills of Los Angeles

Introduced SpeciesIntroduced 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 Carolina

Kudzu: Native to Japan and China, kudzu was introduced into the US as an ornamental and for erosion control.

It can grow as much as a foot-a-day.

The Vine That Ate the South

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

The fishing industry– Has caused significant reduction in populations

of certain game fish

Bluefin tuna auction in Japan fish market

http://www.montereybayaquarium.org/cr/SeafoodWatch/web/sfw_regional.aspx?region_id=0 (seafood guide)

Disruption of Interaction NetworksThe extermination of keystone species by humans can lead to major changes in the structure of communities

Pollinating flying fox Urchin munching sea otter

Population ConservationPopulation conservation focuses on– population size– genetic diversity– critical habitat

Biologists focusing on conservation at the population and species levels follow two main approaches– Small-population model approach– Declining population approach

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 VortexA 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

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.

Num

ber

of m

ale

bird

s

(a) Population dynamics

(b) Hatching rate

200

150

100

50

01970 1975 1980 1985 1990 1995 2000

Year

Egg

s ha

tche

d (%

)

100

90

80

70

60

50

40

301970-74 1975-79 1980-84 1985-89 1990 1993-97

Years

Minimum Viable Population SizeThe 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

Effective population size– Based on number of males and females that successfully

breed…so smaller than the actual total population count.

– Effective population size is used to estimate MVP

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. (A do-something-before-it’s-too-late philosophy)

Case Study: Decline of the Red-Cockaded Woodpecker

Red-cockaded woodpeckers– Require specific habitat factors for survival

(they like habitat with minimal undergrowth and a good supply of optimal nesting trees)

– 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.

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

Landscape Structure and Biodiversity

The structure of a landscape can strongly influence biodiversity

Fragmentation and EdgesThe boundaries, or edges, between ecosystems are defining features of landscapes

As habitat fragmentation increases and edges become more extensive, biodiversity tends to decrease

(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.

Habitat fragmentation effects

Fragmented Forest

Sprawl

Sprawl fragments wildlife habitat, increasing the amount of development-associated species (e.g., white-tailed deer, Canada goose), at the expense of the more rare development-sensitive species (e.g., eastern bluebird, box turtle).

Size: Population Stability

Populations are typically more stable and sustainable and less susceptible to local extinction in large patches than small patches.

Connectivity

Species movement among habitat patches can be facilitated through the protection of discrete spatial features such as stepping stones and linkages .

Connectivity:   Isolation

Small patches that are connected to other patches generally are more ecologically viable than isolated patches. Species within an isolated habitat patch are highly susceptible to disturbance and degradation from surrounding land uses because species movement (to and from the patch) is limited.

Connectivity:   InterconnectednessInterconnectedness is an important feature of networks, as it facilitates species movement among patches. Small interconnected patches provide cover, resting, and foraging habitats for animals en route to larger habitat patches. But, a network that is designed for connectivity but ignores other principles may have too much linear habitat and edge.

Corridors That Connect Habitat Fragments

A movement corridor– Is a narrow strip of quality habitat connecting

otherwise isolated patches– They promote dispersal and help sustain

populations

In areas of heavy human use– Artificial corridors are sometimes constructed

Wildlife bridge in Banff

Establishing Protected Areas

Protected areas are established to slow the loss of biodiversity

A lot of the focus on establishing protected areas has been on hot spots of biological diversity

Biodiversity Hot SpotsA biodiversity hot spot is a relatively small area with an exceptional concentration of endemic species (specific confined to a certain geographic area) and a large number of endangered and threatened species

Terrestrial biodiversity hot spots

Equator

Rain Forest

Philosophy of Nature ReservesNature 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

Often 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

Wyo

min

g

Idah

o

43

42

41

40

0 50 100

Kilometers

Snake R.

Yellowstone National Park

Shoshone R.

Montana

Wyoming

Montana

Idaho

Mad

ison

R.

Gal

latin

R.

Yellowstone R.

Yellowstone-to-Yukon initiative

WWF “Heart of Borneo” initiative

http://www.worldwildlife.org/what/wherewework/borneo/WWFBinaryitem16012.pdf

World’s longest insect

Only lungless frog

Restoration Ecology

Restoration ecology attempts to restore degraded ecosystems to a more natural state

One of the basic assumptions of restoration ecology is that most environmental damage is reversible

Tall-grass Prairie restoration/preserve

Movie

Two key strategies in restoration ecology– Are bioremediation and augmentation of ecosystem

processes

Bioremediation– Is the use of living organisms to detoxify ecosystems

Biological augmentation– Uses organisms to add essential materials to a

degraded ecosystem

Sustainable Development

Sustainable development seeks to improve the human condition while conserving biodiversity

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

The field of sustainable development can be conceptually broken into three constituent parts: environmental sustainability, economic sustainability, social-political sustainability