Chapter 8

Biodiversity and Conservation Biology

This lecture will help you understand:

• The scope of Earth’s biodiversity

• Background rates and mass extinction

• Primary causes of biodiversity loss

• The benefits of biodiversity

• Conservation biology

• Biodiversity conservation efforts

Central Case: Saving the Siberian tiger• Although tigers once roamed across Asia, today they are

exceedingly rare and approaching extinction.

• Siberian tigers are the largest cat in the world.

- The Russian Far East mountains house the last remaining Siberian tigers.

- Historically, native people rarely killed tigers.

• Recently, the wild population approached extinction.

- Hunting, poaching, and habitat destruction from road building, logging, and agriculture

• International conservation groups are working to save the species from extinction.

- Research, education, zoos, and captive breeding programs

Biodiversity encompasses several levels

• Humans are diminishing Earth’s diversity of life.

• Biodiversity: sum total of all organisms in an area

- Split into three specific levels:

- Species diversity

- Genetic diversity

- Ecosystem diversity

Species diversity

• Species diversity: the number or variety of species in the world or in a particular region

- Species richness: the number of species

- Evenness or relative abundance: extent to which numbers of individuals of different species are equal or skewed

- Speciation generates new species and adds to species richness.

- Extinction reduces species richness.

The taxonomy of species

• Taxonomists: scientists who classify species

- Common ancestry, ability to interbreed

- Genera: related species are grouped together

- Families: groups of genera

• Every species has a two-part scientific name: genus and species.

Subspecies: the level below a species• Subspecies: populations of species that occur in different

areas and differ slightly from each other

- Divergence stops short of separating the species.

- Subspecies are denoted with a third part of the scientific name.

Siberian tiger = Panthera tigris altaica

Bengal tiger = Panthera tigris tigris

All subspecies of tigers have disappeared from 93% of their historic range.

Genetic diversity• Encompasses the differences in DNA among

individuals within species and populations

• The raw material for adaptation to local conditions

• Populations with higher genetic diversity can survive.

- They can cope with environmental change.

• Populations with low genetic diversity are vulnerable.

- To environmental change

- Disease

- Inbreeding depression: genetically similar parents mate and produce defective offspring

Ecosystem diversity

• Ecosystem diversity: the number and variety of ecosystems

• It also encompasses differing communities and habitats.

- Sizes, shapes, and interconnectedness of patches within habitats, communities, or ecosystems

Some groups contain more species than others

• Species are not evenly distributed among taxonomic groups.

- Insects predominate over all other life-forms.

- 40% of all insects are beetles.

• Groups accumulate species by:- Adaptive radiation- Allopatric speciation- Low rates of extinction

Measuring biodiversity is not easy

• Species richness is a good gauge for overall biodiversity.

• Out of our “best guess” estimates of 5–30 million species on Earth, only 1.7–2 million species have been identified and described.

• Very difficult to identify species

- Small organisms are easily overlooked.

- Many species look identical until closely examined.

- Many remote spots on Earth remain unexplored.

Biodiversity is unevenly distributed• Living things are distributed unevenly across Earth.

• Latitudinal gradient: species richness increases toward the equator

- Equatorial regions have higher plant productivity, stable climates, and no glaciation.

- Diverse habitats increase niches, which increase species diversity.

- Ecotones (areas where habitats intermix) often have higher diversity.

• Human disturbance can increase habitat diversity.

- But only at the local level

Biodiversity losses and species extinction

• Extinction: occurs when the last member of a species dies and the species ceases to exist

• Extirpation: the disappearance of a particular population from a given area, but not the entire species globally

- Can lead to extinction

• Paleontologists estimate 99% of all species are now extinct.

• Background rate of extinction: natural extinctions for a variety of reasons

- Mammal and marine species: 1 species out of 1,000 become extinct every 1,000 to 10,000 years, which translates to:

- 1 extinction per 1–10 million species

Earth has experienced five mass extinctions• In the past 440 million years, mass extinctions have

eliminated at least 50% of all species.

• Dinosaurs went extinct at the end of the Cretaceous period (65 million years ago) from an asteroid impact.

The current mass extinction is human caused

• During our modern era (Quaternary period), we may lose more than half of all species.

• Today’s extinction event differs from others because it is…

- Caused by humans, and

- Humans will suffer because of it

• The current global extinction rate is 100 to 1,000 times greater than the background rate.

- This rate will increase tenfold in future decades.

People have hunted species to extinction for millennia

Extinctions followed human arrival on islands and continents.

Current extinction rates are higher than normal• The Red List: an updated list of species facing high

risks of extinctions

- 22% of mammal species

- 12% of bird species

- 16–86% of all other species

• Since 1970, 58 fish species, 9 bird species, and 1 mammal species have gone extinct.

- In the U.S. in the last 500 years, 236 animal and 17 plant species are confirmed extinct.

- Actual numbers are undoubtedly higher.

Biodiversity loss is more than extinction

• Population is declining

- Accompanied by shrinking geographic ranges

• Genetic, ecosystem, and species diversity are being lost.

• The Living Planet Index summarizes trends in populations.

- Between 1970 and 2003, the Index fell by 30%.

Biodiversity loss has many causes• Reasons for biodiversity losses are

multifaceted, complex, and hard to determine.

• Four primary causes of population decline are:

- Habitat alteration

- Invasive species

- Pollution

- Overharvesting

• Global climate change now is the fifth cause.

• Each factor is intensified by human population growth and resource consumption.

Habitat alteration causes biodiversity loss• The greatest cause of biodiversity loss

- Farming simplifies communities

- Grazing modifies grassland structure and species composition

- Clearing forests removes resources that organisms need.

- Hydroelectric dams turn rivers into upstream reservoirs and affect floodplains downstream.

- Urbanization and suburban sprawl reduce natural communities.

- A few species (i.e., pigeons, rats) benefit from changing habitats.

Less than 1% of North America’s Great Plains remains, and grassland bird populations have declined 82–99%.

Habitat alteration occurs in every biomeParticularly in tropical rainforests, tropical dry forests, and savannas

Invasive species cause biodiversity loss• Introduction of non-native species to new

environments

- Accidental: zebra mussels

- Intentional: food crops

• Island species haven’t evolved defenses and are very vulnerable.

- Invaders have no natural predators, competitors, or parasites.

• Cost billions of dollars in economic damage each year

Examples of exotic species causing problems

Pollution causes biodiversity loss

• Harms organisms in many ways

- Air pollution degrades forest ecosystems.

- Water pollution adversely affects fish and amphibians.

- Agricultural runoff harms terrestrial and aquatic species.

- The effects of oil and chemical spills on wildlife are dramatic and well known.

• Although pollution is a substantial threat…

- It tends to be cause less damage than habitat alteration or invasive species.

Overharvesting causes biodiversity loss• Vulnerable species are large, few in number, long-lived, and

have few young (K-selected species).

- The Siberian tiger is hunted without rules and regulations.

- The early 1990s saw increased tiger poaching because of powerful economic incentives.

- Many other species affected: Atlantic gray whale, sharks, gorillas

Today the oceans contain only 10% of the large animals they once did.

Climate change causes biodiversity loss• Our manipulation of earth’s climate system is

having global impacts on biodiversity.

• Emissions of greenhouse gases warm temperatures.

- Modifies global weather patterns and increases the frequency of extreme weather events

- Increases stress on populations and forces organisms to shift their geographic ranges

• Most animals and plants will not be able to cope.

Warming has been the greatest in the ArcticThe polar bear has been listed on the U.S. endangered species list.

Biodiversity loss has causes and consequences

Biodiversity benefits: free ecosystem services

• Provides food, shelter, fuel

• Purifies air and water and detoxifies wastes

• Stabilizes climate, moderates floods, droughts, wind, temperature

• Generates and renews soil fertility and cycles nutrients

• Pollinates plants and controls pests and disease

• Maintains genetic resources

• Provides cultural and aesthetic benefits

• Allows us to adapt to change

The annual value of just 17 ecosystem services = $16 - 54 trillion per year

Biodiversity benefits: maintain ecosystem function

• Biodiversity increases the stability and resilience of communities and ecosystems.

- Decreased biodiversity reduces a natural system’s ability to function and provide services to our society.

• The loss of a species affects ecosystems differently.

- Extinction of a keystone species may cause other species to decline or disappear.

Biodiversity benefits: enhanced food security• Genetic diversity in crops is

enormously valuable.

- Turkey’s wheat crops received $50 billion worth of disease resistance from wild wheat.

• New potential food crops are waiting to be used.

- Serendipity berry produces a sweetener 3,000 times sweeter than sugar.

- Salt tolerant grasses can be irrigated with seawater.

Organisms provide drugs and medicines

• Each year pharmaceutical products owing their origin to wild species generate up to $150 billion in sales.

- The rosy periwinkle produces compounds that treat Hodgkin's disease and leukemia.

Biodiversity benefits: economic benefits

• Biodiversity provides a source of income through tourism.

- Ecotourism: people visit natural areas, creating economic opportunity for residents living near those areas

- Costa Rica: rainforests

- Australia: Great Barrier Reef

- Belize: reefs, caves, and rainforests

• A powerful incentive to preserve natural areas and reduce impacts on the landscape and species

• But too many visitors to natural areas can degrade the outdoor experience and disturb wildlife

Biodiversity benefits: people value nature• Biophilia: connections that humans subconsciously seek

with life

- Our affinity for parks and wildlife

- Keeping of pets

- High value of real estate with views of natural lands

• Nature deficit disorder: alienation from the natural environment

- May be behind the emotional and physical problems of the young

Do we have ethical obligations to other species?

• Many feel that living organisms have an innate right to exist.

- Biodiversity conservation is justified on ethical grounds.

- “If tigers aren’t worth saving, then what are we all about? What is worth saving?”

• Despite our ethical convictions, and biodiversity’s many benefits, the future of biodiversity remains far from secure.

Conservation biology responds to biodiversity loss• Conservation biology: studies the factors that influence

the loss, protection, and restoration of biodiversity

- Scientists became alarmed at the degradation of natural systems.

- Applied and goal-oriented, it tries to minimize human impacts.

• Conservation geneticists: study genetic attributes of organisms to infer the status of their population

- Minimum viable population: how small a population can become before it runs into problems

• Conservation biologists try to learn how likely a population is to persist or go extinct, particularly small and isolated ones.

Island biogeography

• Protecting habitat and species requires thinking and working at the landscape level.

• Equilibrium theory of island biogeography: explains how species come to be distributed among oceanic islands

- Also applies to “habitat islands” — patches of one habitat type isolated within a “sea” of others

- Explains how the number of species on an island results from an equilibrium between immigration and extirpation

- Predicts an island’s species richness based on the island’s size and distance from the mainland

Species richness results from island size and distance

• Fewer species colonize an island far from the mainland.• Large islands have higher immigration rates.• Large islands have lower extinction rates.

The species-area curve• Area effect: large islands contain more species than small

islands

- They are easier to find, and their larger populations have lower extinction rates.

- They possess more habitats.

The number of species on an island doubles as the island size increases tenfold.

Small “islands” of habitat rapidly lose species

• Forests are fragmented by roads and logging.

• Small forest fragments lose diversity fastest.

- Starting with large species

Should conservation focus on endangered species?

• Endangered Species Act (1973) (ESA): forbids the government and private citizens from taking actions that destroy endangered species or their habitats

- To prevent extinction

- Stabilize declining populations

- Enable populations to recover

• As of 2008, the U.S. had 1,046 species listed as endangered and 307 listed as “threatened.”

Despite opposition, the ESA has had successes• Peregrine falcons, brown pelicans, bald eagles, and others

have recovered and are no longer listed as endangered.

• Intensive management has stabilized other species.

- The red-cockaded woodpecker

- 40% of declining populations are now stable.

• These successes occur despite underfunding of the U.S. Fish and Wildlife Service and the National Marine Fisheries Service.

- Recently, political forces have attempted to weaken the ESA.

- In 2006, 5,700 U.S. scientists wrote letters of protest to Congress.

The ESA is controversial• Most Americans support protecting endangered

species.

• Opponents feel that the ESA values endangered organisms more than the livelihood of people.

- Private land use will be restricted if an endangered species is present.

- “Shoot, shovel, and shut up”: landowners conceal the presence of endangered species on their land

• But the ESA has stopped few development projects.

- Habitat conservation plans and safe harbor agreements: landowners can harm species if they improve habitat for the species in other places

Other countries have their own version of the ESA• Species at Risk Act (2002): Canada’s endangered

species law

- Stresses cooperation between landowners and provincial governments

- Criticized as being too weak

• Other nations’ laws are not enforced.

- The Wildlife Conservation Society has to help pay for Russians to enforce their own anti-poaching laws.

Protecting biodiversity• Captive breeding: individuals are bred and raised with the

intent of reintroducing them into the wild

- Zoos and botanical gardens

• Some reintroductions are controversial.Ranchers opposed the reintroduction of wolves to Yellowstone National Park.

Some habitats are so fragmented, a species cannot survive.

Protecting biodiversity• Cloning: a technique to create more individuals

and save species from extinction

- DNA from an endangered species is inserted into an egg, which is implanted into a surrogate mother.

- Most biologists agree that these efforts are not adequate to recreate the lost biodiversity.

• Ample habitat and protection in the wild are needed to save species.

Umbrella species

• Conservation biologists use particular species as tools to conserve communities and ecosystems.

- Protecting the habitat of these umbrella species helps protect less-charismatic species that would not have generated public interest.

• Flagship species: large and charismatic species used as spearheads for biodiversity conservation

- The World Wildlife Fund’s panda bear

• Some organizations are moving beyond the single species approach to focus on whole landscapes.

International conservation efforts

• UN Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) (1973): protects endangered species by banning international transport of their body parts

• Convention on Biological Diversity (1992): - Seeks to conserve biodiversity - Use biodiversity in a sustainable manner - Ensure the fair distribution of biodiversity’s

benefits- By 2008, 188 nations had signed on.- Iraq, Somalia, the Vatican, and the U.S. did not

join.

Biodiversity hotspots

• Biodiversity hotspots: an area that supports a high number of species- Endemic species:

species found nowhere else in the world

- The area must have at least 1,500 endemic plant species (0.5% of the world total).

- It must have lost 70% of its habitat due to human impact.

There are 34 global biodiversity hotspots

2.3% of the planet’s land surface contains 50% of the world’s plant species and 42% of all terrestrial vertebrate species.

Community-based conservation

• Protecting habitats makes good sense, but this affects people living in and near these areas.

• Community-based conservation: conservation biologists actively engage local people in protecting land and wildlife- Projects provide education, retraining, and paid

salaries to protect animals from poachers.- Protecting land protects resources from being

used up or sold to foreign corporations.

Conclusion• Loss of biodiversity threatens to result in a mass

extinction event equivalent to mass extinctions of the past.

• Primary causes of biodiversity loss are:- Habitat alteration, invasive species, pollution,

overharvesting of biotic resources, and climate change

• Human society cannot function without biodiversity’s benefits.

• Science can help save species, preserve habitats, restore populations, and keep natural ecosystems intact.

QUESTION: Review

Which level is NOT included in the concept of biodiversity?

a) Speciesb) Geneticsc) Ecosystemsd) All of the above are included in this concept.

QUESTION: ReviewWhat happens when a species experiences “inbreeding depression”?

a) The species becomes too large for the resource base

b) Genetically similar parents mate and produce inferior offspring

c) Genetically similar parents mate and produce superior offspring

d) The number and variety of species increasese) An ecosystem’s biodiversity increases

QUESTION: ReviewAccording to the concept of “latitudinal gradient,” which of the following happens?

a) Species richness increases toward the equatorb) Species richness decreases toward the

equatorc) Species richness decreases over timed) Countries like Canada have many more

species than expectede) People in warmer climates protect species

better than people in colder climates

QUESTION: Review

Which of the following statements is FALSE?

a) Very small species are often overlooked.b) Remote areas may have unidentified species.c) We have identified almost all species on Earth.d) There are more insect species than any other

type of species.e) Ecotones often have high biodiversity.

QUESTION: Review

Which of the following is the major cause of extinction?

a) Invasive speciesb) Pollutionc) Habitat lossd) Overharvestinge) These are pretty much equal in causing

extinction.

QUESTION: Review

Biodiversity does all of the following EXCEPT:

a) Provide ecosystem servicesb) Decrease food securityc) Maintain ecosystem functiond) Provide aesthetic benefitse) Provide economic benefits

QUESTION: Review

According to the theory of island biogeography, which island would have the LOWEST species richness?

a) A large island, close to the mainlandb) A large island, far from the mainlandc) A small island, close to the mainlandd) A small island, far from the mainlande) None of these; islands don’t really have

species

QUESTION: Review

A “biodiversity hotspot” is:

a) An area located near the equatorb) An area that supports few, but large,

speciesc) An area that contains naturally high

numbers of peopled) An area that contains a large number of

endemic speciese) An area where the wealthy can go on

vacation

QUESTION: ReviewWhich statement about the U.S. Endangered Species Act is FALSE?

a) It forbids the government, but not private citizens, from harming endangered species.

b) It lists endangered and threatened species.c) It is designed to prevent extinction.d) It is designed to enable populations to

increase.e) It is designed to stabilize declining

populations.

QUESTION: Weighing the Issues

If a pharmaceutical company produces a medicine from a plant found in Costa Rica that will earn millions of dollars, who should reap the financial benefits?

a) The company, because it had to pay millions of dollars to discover and produce the drug

b) Costa Rica, because it had the plant that produced the drug

c) Taxpayers, because they fund lots of research through their tax dollars

d) Native people in Costa Rica, because the company would not have found the drug without their help

e) The native people, the company, and Costa Rica, because all played a vital part in the drug’s discovery and development

QUESTION: Weighing the IssuesHave you ever personally experienced evidence of the biophilia hypothesis?

a) Yes, I frequently feel a connection to other living things and nature

b) Yes, sometimes, on a particularly lovely day

c) Maybe, but I’m not sured) No, because I don’t get to experience

nature often enough e) Definitely not, unless I was going to earn

money from using nature

QUESTION: Interpreting Graphs and DataWhere would ecotourists go to view the maximum species richness on these islands?a) Redonda b) Montserrat c) Puerto

Ricod) Hispaniola e) Jamaica

QUESTION: Interpreting Graphs and DataWhich biome lost the most area by 1950? Which biome lost the most area in recent decades?

a) Temperate grassland, tropical dry forest

b) Desert, savanna

c) Chaparral, tundra

d) Temperate grassland, desert