Chapter 56 Conservation Biology and Restoration Ecology.
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Transcript of Chapter 56 Conservation Biology and Restoration Ecology.
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