57Conservatio

n Biology

57 Conservation Biology

• 57.1 What Is Conservation Biology?

• 57.2 How Do Biologists Predict Changes in Biodiversity?

• 57.3 What Factors Threaten Species Survival?

• 57.4 What Strategies Do Conservation Biologists Use?

57.1 What Is Conservation Biology?

Conservation biology is an applied science, devoted to preserving the diversity of life.

Conservation biology is integrated with other disciplinesgenetics, evolution, population

ecology, biogeography, wildlife management, economics, and sociology

Photo 57.3 Pine cones open after fire.

Photo 57.4 Cones of ponderosa pine will not germinate until opened by fire.

57.1 What Is Conservation Biology?

Conservation biologists are motivated by the belief that

loss of biodiversity is negative.

Photo 57.7 Madagascar periwinkle (Catharanthus roseus), source of antileukemia drugs.

Conservation biology is guided by the following three principles:

• Evolution is the process that unites all of biology.

• The ecological world is dynamic.

• Humans are part of ecosystems.

Photo 57.10 Arabian oryx, saved from extinction by captives being reintroduced into the wild.

Photo 57.14 Northern spotted owl (Strix occidentalis caurina) is dependent on old-growth forest.

Figure 57.1 Extinct Australian MegafaunaHuman beings have caused extinctions of other species for thousands of years.

• 1st humans in N. America 20,000 ya

• probably caused the extinction of large mammals

• similar extinction in Australia 40,000 ya

When Polynesian people settled Hawaii 2,000 years ago…

exterminated at least 39 endemic species of birds (species found nowhere else in the world)

But the current extinction situation is unique…how?

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 pleasureaesthetic pleasure from watching and interacting with other species.

Photo 57.8 Bark of Pacific yew (Taxus brevifolia); chemicals extracted from bark treat cancer.

Figure 57.2 Back from Extinction?

In 2004, the ivory-billed woodpecker In 2004, the ivory-billed woodpecker was believed to have been glimpsed was believed to have been glimpsed in Arkansas after 60 years without a in Arkansas after 60 years without a siting.siting.

Estimating rates of extinction

species–area relationship: As area decreases, number of species decreases.

~ 90% loss in habitat ~ 50% loss of species

57.2 How Do Biologists Predict 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 If this rate of loss continues, at least 1 million species will be least 1 million species will be lost from this biome in this lost from this biome in this century.century.

Figure 57.3 Deforestation Rates are High in Tropical Forests

57.3 What Human Activities Threaten Species Survival?

• Habitat destructionHabitat destruction

• Introduction of exotic speciesIntroduction of exotic species

• OverexploitationOverexploitation

• Climate changeClimate change

HABITAT LOSS

• most important cause of endangerment in U.S., especially in freshwater

• habitat is increasingly fragmented

Figure 57.4 Proportions of U.S. Species Extinct or Threatened

Figure 57.5 Edge Effects

Small patches can support only Small patches can support only small populations (greater risk small populations (greater risk of extinction).of extinction).

Figure 57.6 Species Losses Have Been Studied in Brazilian Forest Fragments

ANIMATIONANIMATION

Photo 57.20 Clear cuts on private timber land, Coos Bay, OR.

Photo 57.23 Satellite image of Rondonia State, Brazil

19751975 19861986 19921992

Photo 57.19 Remains of southern beech forests burned to create cattle pasture; southern Chile.

Figure 57.7 Habitat Corridors Facilitate Movement (Part 1)

Figure 57.7 Habitat Corridors Facilitate Movement (Part 2)

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.

Figure 57.8 Endangered by Medical Practices

Intentional & Accidental Invasive Species

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

57.3 What Factors Threaten Species Survival?

• rabbits, intro. to Australia for sport hunting. Many small marsupials competition

with rabbits; predation by introduced cats, dogs, and foxes

• brown tree snake, Guam 1940svery high densities nowcaused the extinction of 15 bird

species, including three endemics

Figure 57.9 Agent of Extinction

More Examples

Chestnut blight

Dutch elm disease of trees

Avian malaria

Photo 57.9 Tree with Dutch elm disease; Great Falls, MT.

Climate Change Change in Species Distributions

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

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

Increasing sea surface temperatures…problem?

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

Photo 57.21 Urbanization of a former estuary south of San Francisco, CA.