Chapter 57

Conservation Biology

Conservation Biology• Conservation biology is an applied science,

devoted to preserving the diversity of life.

• Conservation biology is integrated with other disciplines, using knowledge from genetics, evolution, population ecology, biogeography, wildlife management, economics, and sociology.

Conservation biology is guided by the followingthree principles:

• Evolution is the process that unites all of biology.

• The ecological world is dynamic.

• Humans are part of ecosystems.


• The current extinction situation is unique.

• For the first time, all major environmental changes on Earth are human induced, and we are aware of what we are doing.


Why do we value biodiversity?

• We depend on other species for food, fiber, and medicines.

• Species are necessary for the functioning of ecosystems which provide us with so many goods and services.

• We derive enormous aesthetic pleasure from watching and interacting with other species.


• Extinctions deprive us of the opportunity for scientific study and understanding ecological interactions.

• Extinctions raise many ethical concerns; all species are judged to have intrinsic value.


Changes in BiodiversityScientists cannot accurately predict the number ofextinctions in the coming century for four reasons:

• The number of species currently on Earth is unknown.

• We do not know exactly where species live.

• It is difficult to determine when a species actually becomes extinct.

• We do not know what will happen in the future, including natural events, and what humans will do.

• Rates of extinction are estimated in several ways.

• The species–area relationship is a well-established tool. As area decreases, number of species decreases.

• On average, a 90 percent loss in habitat will result in a 50 percent loss of species.

Changes in Biodiversity

• The current rate of loss of tropical evergreen forest (the most species-rich biome) is about 2 percent per year.

• If this rate of loss continues, at least 1 million species will be lost from this biome in this century.


Figure 57.3 Deforestation Rates are High in Tropical Forests

• Biologists use computer models to estimate the probability that a population will go extinct.

• Species in imminent danger of extinction are labeled endangered.

• Threatened species are likely to become endangered in the near future.


• Species whose populations are suddenly shrinking are at high risk. Also species with highly specialized food or habitat requirements.

• Small populations can easily be wiped out by natural disasters, such as fire.


Factors Threatening SpeciesHuman activities that threaten survival of otherspecies include the following:

• Habitat destruction

• Introduction of exotic species

• Overexploitation

• Climate change

• Until recently, humans caused extinctions mainly by overhunting.

• Some species are still threatened today. Elephants and rhinoceroses are killed for their tusks and horns.

• Powdered rhinoceros horn is used in traditional Chinese medicine. An attempt to replace it with saiga antelope horn worked so well that it is now endangered.

Factors Threatening Species

Figure 57.8 Endangered by Medical Practices

• Humans move many species to regions outside their original range, both intentionally and accidentally.

• Some exotic species become invasive. They spread widely and become extremely abundant, often at a cost to native species.


• Global warming will increase average temperatures by 2°C–5°C by the end of this century.

• Species will have to shift ranges to remain in the same temperature regimes.

• Some habitats, such as alpine tundra, may be completely eliminated.


• Increasing sea surface temperatures are threatening corals.

• High temperatures cause them to expel their photosynthetic endosymbiotic dinoflagellates—called bleaching. Death can result.

• Forty percent of coral reefs worldwide are likely to be killed off by 2010.


Figure 57.10 Global Warming Threatens Corals

Strategies for Conservation• Establishing protected areas is an important part

of efforts to preserve biodiversity.

• Protected areas preserve habitat and prevent human exploitation.

• They can act as nurseries from which individuals can disperse, replenishing populations that might otherwise go extinct.

• Conservation biologists have identified 595 “centers of imminent extinction” which have threatened species found nowhere else.

• The sites harbor 794 species considered to be at serious risk of extinction.

• Only one-third of the sites are legally protected. Most are surrounded by rapid human development and are in urgent need of protection.


Figure 57.13 Centers of Imminent Extinction

• Some degraded ecosystems can be restored.

• In restoration ecology, methods are being developed to restore degraded habitats.


• Restoration often requires restoring disturbance patterns.

• Many species depend on disturbances such as fire, windstorms, grazing.

• Humans often try to reduce such disturbances. For example fire suppression was official policy for many years. Controlled burning is now used in many forest and grassland management programs.


• Conservation biologists try to determine the historical patterns of disturbance.

• Annual rings of trees reveal scars from fires that were not intense enough to kill the trees.


Figure 57.15 The Frequency and Intensity of Fires Affect Ecosystems (A)

• Although new habitats can be created, developing a fully functioning ecosystem that supports many species is not easy.

• Many development projects destroy habitat, but they are permitted as long as the developer promises to create new habitat to replace the one being destroyed.


• The Convention on International Trade in Endangered Species (CITES) is an international treaty to decrease trade in endangered species, or any parts of these species—e.g., whale meat, rhinoceros horn, parrots, orchids, etc.

• For some items, such as elephant ivory, the demand remains strong, so poaching is common.


• The best way to control invasive species is to prevent their introduction.

• Many aquatic species have been carried unintentionally in ship ballast water. This water could be deoxygenated, which would kill any organisms, and also extend the life of ballast tanks.


• Protected areas alone cannot preserve biodiversity; even regions where people live can also contribute.

• Using these lands in ways that sustain biodiversity is known as reconciliation ecology.


• Some of the world’s most endangered species are held in captivity while threats to their habitats are reduced.

• There is not enough space in zoos to maintain adequate populations, but captive breeding programs have played an important role during critical periods.

• These programs also raise public awareness.


• We can make an analogy to Earth today: the loss of species suggests that the load of human activities has pushed the hull of Noah’s ark below the Plimsoll line.

• Science cannot determine an “acceptable rate of loss.” Ethical considerations must figure prominently in the decisions that society makes.


Education

Chapter 57