Conservation Biology Flashcards

Ch 58 Conservation Biology

• Scale of current mass extinction and major underlying causes.

• Hotspots and their importance.

Biodiversity Crisis

• Currently experiencing a mass extinction event comparable to past events.

• Majority of recent extinctions have occurred since 1900.

• Estimated that 20% of present-day species may be extinct by the middle of the century. Includes:

  • 2,000 of the world's 10,000 species of birds

  • 50,000 of the world's 250,000 species of plants

  • 4,000 of the world's 20,000 species of butterflies

Homo sapiens

• After humans arrived:

  • In North America, 74% to 86% of megafauna became extinct.

  • In Australia, all megafauna went extinct.

• Caused by hunting and burning/clearing of forests.

Islands

• Majority of extinctions have occurred on islands.

  • 60% of recent mammal extinctions occurred on islands.

• Why?

  • Evolved in the absence of predators.

  • Humans introduced competitors and diseases.

  • Island populations are usually small, increasing their risk for extinction.

Hotspots

• Endemic species: species found naturally in only one geographic area and nowhere else.

• Hotspots: areas where species have high endemism and are disappearing at a rapid rate.

• Examples:

  • Madagascar

  • Tropical Andes

  • Philippines

  • Cape Floristic Province

  • California Floristic Province

  • Caucasus

  • Mediterranean Basin

  • Mountains of South-Central China

  • Caribbean

  • Polynesia & Micronesia

  • Western Ghats & Sri Lanka

  • Indo-Burma

  • Mesoamerica

  • Chocó

  • Brazilian Cerrado

  • Guinean Forests of West Africa

  • Eastern Arc Mountains & Coastal Forests

  • Wallacea

  • Sundaland

  • Central Chile

  • Atlantic Forest

  • Succulent Karoo

  • New Caledonia

  • Southwest Australia

  • New Zealand

Why Do Hotspots Contain So Many Endemic Species?

• Hotspots can be found in:

  • Areas of high species diversity.

  • Isolated islands.

  • Regions with a high species diversification rate.

• Hypotheses:

  • High rates of speciation in transition zones between different types of habitats.

Amphibian Extinction Crisis

• 43% of amphibian species experienced decreases in population size.

• 1/3 are threatened with extinction.

• Examples:

  • Venezuela: Dendrobates leucomelas

  • Panama: Atelopus zeteki

  • Madagascar: Mantella aurantiaca

  • Australia: Litoria caerulea

Causes of Amphibian Declines

• Many species have declined in pristine, well-protected habitats.

• Particularly sensitive to the state of the environment:

  • Chemicals pass into their body because of their moist skin.

  • Larval habitats are aquatic, so they need high water quality.

  • Eggs do not have protective coverings and are particularly sensitive to damage like UV radiation.

• No single cause for amphibian decline is apparent.

• Different species are afflicted by different problems.

• Global environment is deteriorating in many different ways.

Value of Biodiversity

• Direct economic value includes resources for our survival:

  • Sources of food, medicine, clothing, and shelter.

  • Food crop genetic variation.

  • May be needed in the future to improve crops.

  • 40% of prescription and nonprescription drugs have active ingredients extracted from plants.

Plants of Pharmaceutical Importance

• Rosy Periwinkle: vinblastine and vincristine effectively treat common forms of childhood leukemia.

• Cancer-fighting drugs developed from the bark of the Pacific yew.

Indirect Economic Value

• Indirect economic value is derived from ecosystem services:

  • Maintain quality of natural water, buffer against storms and droughts.

  • Prevent loss of minerals and nutrients.

  • Moderate local and regional climate.

  • Absorb pollution.

  • Promote breakdown of organic wastes and cycling of minerals.

Value of Intact Habitats

• Economists compare the value of intact habitats compared to destroying those habitats.

• Coastal mangrove habitats in Thailand: Timber, charcoal production, offshore fisheries, and storm protection vs. shrimp farming.

• Economic Value (US$ per hectare):

  • Intact Mangrove, Thailand: Approximately 80,000

  • Shrimp Farming: Significantly lower value

New York City Watersheds

• 90% of the water for the 20 million people in New York comes from the Catskill Mountains and Delaware River.

• Dilemma: Protect functioning ecosystem or construct filtration plants.

• To build plants cost 6 billion.

• Annual operating cost 300 million/year - 3 billion over 10 years.

• Spend 1 billion over 10 years to preserve the ecosystem.

Unknown Costs of Species Losses

• The value of an ecosystem or a species may not be clear until it is lost.

• Ecological Economics: the study of how the societal benefits provided by species and ecosystems can be appropriately valued.

Habitat loss

• 10-fold increase in area -> doubling in the number of species

• Rainforest in Madagascar:

  • 90% habitat loss

  • 16 of 31 primate species are threatened

  • Many species have become extinct

Case Study: Songbird Declines

• Migrant songbirds have declined severely.

• Nest in northern forests in summer but spend winter in South or Central America or the Caribbean Islands.

• Only about half as many birds fly over the Gulf of Mexico each spring as in the 1960s.

• Culprit:

  • Habitat fragmentation and loss.

  • Availability of winter habitat declined.

Habitat Fragmentation

• Disastrous consequences of dividing habitat up into small areas.

• Smaller populations go extinct more easily.

• Environment on edge of habitat is different.

Habitat Fragmentation - Manaus, Brazil

• Landowners in Manaus, Brazil, preserved patches of rain forest to test patch size vs. species extinction.

• Smaller patches had higher Extinction rates.

• Army ants lost in smaller plots.

• Even largest patches lost half of bird species in less than 15 years.

Vulnerability of Small Populations

• Small populations are vulnerable to extinction.

• Disaster or random bad luck can cause extinction.

• Heather hen example:

  • Hunted to small numbers on Martha's Vineyard.

  • Wiped out by fire, then predation, then disease.

Lack of Genetic Variability

• In small populations, genetic drift leads to loss of alleles.

• More genetically variable individuals tend to have greater fitness.

• Extinction vortex: Lack of variability -> less fitness -> smaller population -> lack of variability -> less fitness ->

Prairie Chickens

• Population crash due to agriculture.

• Small populations lose genetic variation.

• At one point Only 1 dominant male.

• Transplant birds from other populations into Illinois.

• Population starts to recover.

Introduced Species

• Introduced species threaten native species and habitats.

• Naturally rare, but now all too common due to humans.

• Arrive within ship cargo/ballast.

Consequences of Introduced Species

• 50,000 species have been introduced in the United States.

• Effects:

  • Huge economic costs - estimated 140 billion per year.

  • Human health: West Nile fever

  • Hawaii: mosquitoes brought malaria; 70% native fauna extinct or restricted to high elevations.

Widespread Effects

• Effect may not be direct, but spread through the ecosystem.

• Argentine ant has spread through much of the southern U.S. Negative effect on coast horned lizard which feeds on native ants.

• Native ants spread seeds, introduced ones do not.

Ecosystem Transformation

• Introduced species may overrun a habitat and displace native species.

• Yellow star thistle in California now covers what was once grassland.

• In Hawaii, a small tree from the Canary Islands has transformed the soil:

  • It can fix nitrogen at high rates.

  • New nitrogen-requiring species have invaded.

Introduced Species - Nile Perch

• Sometimes species are introduced for economic purpose

• Nile perch in Lake Victoria - OK for a while but then imbalance causes explosion driving many cichlid (prey) species to extinction

• Overfishing and lack of prey causing crash in perch population

Extinction Cascade

• Effects on one species can have ramifications throughout an ecosystem.

• Can cause an extinction cascade.

• Large impact if effects reach keystone species.

• Trying to eradicate or even control invasive species is expensive and often not effective.

• Many unforeseen consequences.

• Easiest to prevent the original invasion.

Case Study: Alaskan Near-Shore Habitat

1. Whales: Overharvesting of plankton-eating whales may have caused an increase in plankton-eating pollock populations.

2. Nutritious fish: Populations of nutritious fish like ocean perch and herring declined, likely due to competition with pollock.

3. Sea lions and harbor seals: Sea lion and harbor seal populations drastically declined in Alaska, probably because the less-nutritious pollock could not sustain them.

4. Killer whales: With the decline in their prey populations of sea lions and seals, killer whales turned to a new source of food: sea otters.

5. Sea otters: Sea otter populations declined so dramatically that they disappeared in some areas.

6. Sea urchins: Usually the preferred food of sea otters, sea urchin populations now exploded and fed on kelp.

7. Kelp forests: Severely thinned by the sea urchins, the kelp beds no longer support a diversity of fish species, which may lead to a decline in populations of eagles that feed on the fish.

Invasive species - Alewives in Great Lakes

• 1932 - Alewives invade Great Lakes from Canadian canal

• 1960s - Reach Lake Michigan

• 1967 - population explodes -> trophic cascade -> algal bloom -> Eutrophication

• Chinook and Coho Salmon introduced

• 2010s - Alewife population so low that Salmon depleted

• Hurting fishing industry

Preserving Species

• Restoring destroyed habitats.

  • E.g., abandoned farmlands.

• Reintroducing/protecting keystone species.

  • Wolves near Yellowstone Park.

Preserving Species - Peregrine Falcon

• DDT banned in 1972.

• But no falcons remained in the eastern US

• Captive breeding program in 1970.

• A strong recovery, restored to its historic range.

Wildlife corridors for fragmented habitats

• Hardberger Park land bridge over Wurzbach parkway

Which species should we save?

• Use phylogenies to help prioritize species for conservation

• Unique traits

• Clues to the past

Multicomponent Conservation Plans

• Due to scale, often need multidimensional plans that combine several efforts

• Conserve pristine nature preserves surrounded by open lands that allow some commercial activity or human impact

  • Means more total area available for populations

  • Wildlife corridors also expand effective area

• Decide on which species are most important to save

• Decide on which species are most able to be saved

• Need wide range of expertise

  • e.g., ecologists AND economists!