Chapter 57
Conservation Biology
Conservation Biology
Introduction
Why Care about Species Extinctions?
Estimating Current Rates of Extinction
Preserving Biodiversity
Habitat Restoration and Species Recovery
Healing Biotas: Conservation Medicine
Setting Limits: The Legacy of Samuel Plimsoll
Introduction
The problem of human-caused __________ of species led to the development of the discipline of conservation biology: the scientific study of how to preserve the diversity of life.
Conservation biology draws on population genetics, evolution, biogeography, wildlife management, economics, and sociology.
Why Care about Species Extinctions?
The value of biodiversity to humans:
Humans depend on other species for food, fiber, and medicine.
Humans derive aesthetic pleasure from interacting with other organisms.
Causing the extinction of other species raises serious __________ issues.
Extinctions make the study of ecological relationships and species interactions difficult.
Species are necessary for the function of the ecosystems of which they are a part.
Why Care about Species Extinctions?
The benefits provided to humans by functioning ecosystems are enormous.
These include, among others, prevention of soil erosion, regulation of hydrologic cycles, and __________ and recycling of waste products.
Why Care about Species Extinctions?
In Western
Cape Province,
The native
vegetation of the highlands is a species-rich community of shrubs called fynbos that can survive drought, nutrient-poor soils, and
fire. The highlands provide two thirds of
The fynbos also provides income in the form of cut flowers and tourism.
The native vegetation is being displaced by introduced plants that grow taller and faster, increase the intensity of fires, and reduce the water supply.
Why Care about Species Extinctions?
By removing the exotic plants and managing fire, the natural fynbos ecosystem can be preserved.
High-tech approaches to replacing water (such as sewage purification plants and desalinization) would cost between 1.8 and 6.7 times as much as maintaining natural vegetation in the watershed.
Estimating Current Rates of Extinction
The number of species on an island increases with the size of the island.
Conservation biologists have applied this ____________________ relationship to habitat patches on the mainland as well.
Findings suggest that a 90% loss of habitat will result in the loss of half of the species living there.
If the current rate continues, about __________ __________ species living in the tropical evergreen forests will become extinct in this century.
Estimating Current Rates of Extinction
To assess extinction risk for a population, biologists analyze many factors including genetic variation, morphology, physiology, behavior, and environment.
Species in imminent danger over a significant portion of their range are labeled endangered species.
Species that are likely to become endangered in the near future are labeled threatened species.
Estimating Current Rates of Extinction
Rarity is not always a reason for concern.
However, species in which a few individuals are confined to a small range are more likely to be eliminated by local disturbances such as fire and disease.
A 12-year
study of grizzly bears in
To achieve a higher probability of survival, or survival for a longer time, more bear habitat would be needed.
Preserving Biodiversity
The human activities that threaten species include habitat destruction, introduction of invasive species, overexploitation, disease, alteration of disturbance patterns, and climate change.
Conservation biologists determine how these activities are affecting species and devise strategies to preserve endangered or threatened species.
Preserving __________
Habitat
loss is the most important cause of endangerment of species in the
As habitats are destroyed, the remaining patches become fragmented (smaller and more isolated).
Small patches cannot maintain populations that require larger areas and can support only small numbers of species that can survive in them.
Preserving Biodiversity
The fraction of a habitat patch that is influenced by adjacent habitat conditions (edge effects) increases rapidly as patch size decreases.
Close to the edges of a forest patch, for example, the environment differs from that inside the forest, so species from surrounding habitats colonize the edges to compete with or prey upon those inside.
Preserving Biodiversity
Usually it is not known which organisms lived in an area before their habitats became fragmented.
A major
research project in
Landowners agreed to preserve forest patches of certain sizes and configurations.
Biologists examined species diversity before and after logging around the patches.
Species began to disappear from the isolated patches soon after the surrounding forest was cut.
Preserving Biodiversity
Species that become extinct in small patches are unlikely to be reestablished, but __________ between patches can allow individuals to disperse and species to persist.
In
Preserving Biodiversity
People have moved organisms between continents deliberately and accidentally.
A species that has evolved in a community and become accustomed to the natural predators or competitors may be driven to extinction by newly introduced predators or competitors.
A major human-caused environmental change is the introduction of non-native species that then become invasive in the their new environments.
Preserving Biodiversity
Hundreds of species of plants have been introduced as ornamentals. An example is purple loosestrife.
Almost half
of the medium-sized marsupials in
Proliferation of introduced pathogens, such as the fungus that causes Dutch elm disease, has caused much destruction to North American forests.
Preserving Biodiversity
The best way to reduce the damage caused by invasive species is to prevent their establishment in the first place.
The shipping industry spreads invasive species in ballast water, which is pumped into ships at one port and discharged at another. Deoxygenating ballast water before it is pumped out would control the problem of invasive aquatic species.
Preserving Biodiversity
The
A decision tree can be used to determine whether a species is likely to become invasive.
A plant species is more likely to become __________ if it has __________ generation time, small seeds, a large range, and no evolutionary relationship to plants in the new area.
Conservation
biologists have developed a decision tree to determine whether exotic species
can safely be introduced into
Preserving Biodiversity
Until recently, humans caused most extinctions primarily by overhunting.
The
passenger pigeon, one of the most abundant species of bird in
Elephants and rhinoceroses are threatened with extinction because poachers kill them for their tusks and horns.
The houseplant and pet trades currently threaten many species of orchids, parrots, and reptiles.
Preserving Biodiversity
Programs have been developed to help us use species in a way that does not threaten their survival.
Certification programs: Organizations such as the Forest Stewardship Council (FSC) and the Marine Stewardship Council determine whether commercial operations harvest and market their products in ways that meet their criteria.
Preserving Biodiversity
The Convention on International Trade in Endangered Species (CITES), an international organization, determines and prohibits trade in endangered species or their products (e.g., whale meat, rhinoceros horn, many parrots and orchids).
Preserving Biodiversity
Many species depend on particular patterns of __________ to persist.
Humans often try to control such disturbances, but conservation biologists try to determine where disturbances should be reestablished.
For
example, annual growth rings on ponderosa pines show that low-intensity fires
were once common in
Because of sheep grazing and fire suppression, buildup of dead branches and needles has resulted in intense, tree-consuming fires.
Today ground fires are deliberately started to imitate historic patterns.
Preserving Biodiversity
Atmospheric
scientists predict that average temperatures in
Species will need to shift their ranges as much as 500800 km. Some habitats, such as alpine tundra, may disappear.
Knowledge of how organisms responded to past climate changes, such as postglacial warming, can help us predict the effects of the current warming.
Organisms such as birds, which have good dispersal abilities, can shift their ranges rapidly.
Preserving Biodiversity
Other species shift ranges much more slowly.
In
Earthworms
disperse very slowly. Introduced earthworms from
Slow dispersal, not lack of suitable habitat, has kept native earthworms from moving northward.
Preserving Biodiversity
If Earth warms as predicted, climatic zones wont just __________. New climates will develop and some existing climates will disappear.
New climates are likely to develop at low elevations in the tropics. A warming of even 2°C would result in climates that are warmer than any that exist today.
In 1988, the highest sea surface temperatures ever recorded caused corals to undergo bleaching and increased their mortality worldwide.
Habitat Restoration and Species Recovery
The field of restoration ecology has developed to study methods of restoring natural habitats.
Some damaged habits will not recover without assistance, and biologists try to maintain some endangered species in captivity until suitable habitat is available.
Conservation biologists have only a limited ability to restore natural ecosystems and many attempts have been only partially successful.
Habitat Restoration and Species Recovery
Wetland
restoration is a high priority in southern
In early attempts at species restoration, many species failed to recolonize the wetlands.
Biologists discovered that the problem was lack of __________ in the plant species introduced. Plots later planted with species-rich mixtures developed the complex vegetation needed for birds and insects and accumulated nitrogen more quickly than the species-poor experimental communities.
Habitat Restoration and Species Recovery
Threatened species can sometimes be maintained in captivity while external threats to their existence are reduced or removed.
Captive propagation is a temporary measure, however, because zoos, aquariums, and botanical gardens have only a limited capacity.
Some species have benefited from captive breeding programs.
Habitat Restoration and Species Recovery
Captive breeding is helping to save the California condor.
The condor
once ranged from
Captive breeding was initiated in 1983 and by 1993 the captive breeding population was 60 birds.
Captive-bred
birds were released in
As of 2003
there were 81 wild condors in
Healing Biotas: Conservation Medicine
On land and sea, diseases among wild organisms are threatening biodiversity.
The
In parts of
the
The __________ __________ bird virus has exploded across the U.S. and has spread to humans.
Healing Biotas: Conservation Medicine
A new field of conservation medicine is developing to help identify the causes of increases in wildlife diseases and to devise ways to prevent transmission and limit the effects.
Molecular techniques are used to identify species, strains, and life cycles of pathogens.
Setting Limits: The Legacy of Samuel Plimsoll
In the nineteenth century, Samuel Plimsoll, an English MP, persuaded Parliament to require a load line on the hull of every merchant ship to prevent overloading and thus to reduce the rate of shipwreck.
The increasing loss of Earths species suggests that we need such a Plimsoll line to limit the load of human activities on the planet.
Video 57.1 The exotic invasive plant kudzu, Pueraria lobata
Video 57.2 Portrait of a rainforest ecosystem: The Amazon of South America and other locations
Video 57.3
Portrait of a marine ecosystem: A coral reef in the