Human DisturbancesHuman Disturbancesto Ecosystemsto EcosystemsSustaining Biodiversity

The Passenger Pigeon: The Passenger Pigeon: Gone ForeverGone ForeverOnce the most

numerous bird on earth.

In 1858, Passenger Pigeon hunting became a big business.

By 1900 they became extinct from over-harvest and habitat loss.

I. Endangered and Threatened I. Endangered and Threatened Species: Ecological Smoke AlarmsSpecies: Ecological Smoke Alarms

A. Endangered species: so few individual survivors that it could soon become extinct.

B. Threatened species: still abundant in its natural range but is likely to become endangered in the near future.

II. Species ExtinctionII. Species ExtinctionA. Species can become extinct:

1. Locally: A species is no longer found in an area it once inhabited but is still found elsewhere in the world.

2. Ecologically: Occurs when so few members of a species are left they no longer play its ecological role.

3. Globally (biologically): Species is no longer found on the earth.

3. Globally (biologically): continued.

Some species have become permanently extinct because of human activities.

II. Species ExtinctionII. Species Extinction

Some species have characteristics that make them vulnerable to ecological and biological extinction.

II. Species ExtinctionII. Species Extinction

1. The International Union for the Conservation of Nature and Natural Resources (IUCN) publishes an annual Red List, listing the world’s threatened species.

2. The IUCN takes the following into account:Population Size & Reduction of it

# of Mature Individuals

Geographic Range of Population

Quality of Habitat

Probability of Extinction

B. Scientists use measurements and models to estimate extinction rates.

The border of Haiti and the Dominican The border of Haiti and the Dominican RepublicRepublic

II. Species ExtinctionII. Species ExtinctionC. Causes: Conservation biologists summarize

the most important causes of premature extinction as “HIPPO”:

1. Habitat destruction, degradation, and fragmentation

2. Invasive Species

3. Population growth

4. Pollution

5. Overharvest

H. Habitat loss…Biggest threat to biodiversityWhen area to live is gone, organisms

die

Why would the habitats go away?

Ex. deforestation

Habitat FragmentationSeparation of wilderness areas from

other wilderness areasFragmented areas are like islands; the

smaller the fragment, the less biodiversity it will support

Figure 55.5 Fragmentation of a forest ecosystem

Habitat destruction, degradation, and fragmentation

Reduction in ranges of four wildlife species, mostly due to habitat loss and overharvest.

Biotic and Abiotic Issues of Fragmentation

Biotic:-some organisms need

large areas to gather food

Ex. Lions

Ex. Zebra

-no migratory routes to re-establish populations lost due to natural disasters

Abiotic:-climate can change

-can cause EDGE EFFECT

(different conditions along the boundaries of an ecosystem)

I. Introduction of Exotic (invasive) SpeciesNew orgs introduced into an

ecosystem; do not have any natural predators and is little competition with other orgs, so native species are at risk

Exotics may take over niches of native species and eventually replace the native species completely

Invasive SpeciesMany nonnative species provide us with food, medicine, and other benefits but a few can wipe out native species, disrupt ecosystems, and cause large economic losses.

Kudzu vine was introduced in the Kudzu vine was introduced in the southeastern U.S. to control erosion. It has southeastern U.S. to control erosion. It has taken over native species habitats.taken over native species habitats.

Invasive Species

Many invasive species have been introduced intentionally.

Invasive SpeciesPrevention is the best way to reduce threats from invasive species, because once they arrive it is almost impossible to slow their spread.

PopulationPopulation

Human populations put pressure on species◦Direct use, habitat conversion, pollution

Large numbers of humans use resources wild species need◦ Even if each person uses small amounts of resources

A small group of people can overuse resources◦ People with highly consumptive resources have a

disproportionate effect on the environmentDifferent levels of consumption and numbers of

people drive tensions between countries

Figure 55.0 Deforestation of tropical forests

P. PollutionDamage to habitat by pollutionThree types of pollution: ◦Air◦Water◦Land

O. OverexploitationO. OverexploitationSome protected species are killed for their

valuable parts or are sold live to collectors.

Killing predators and pests that bother us or cause economic losses threatens some species with premature extinction.

Legal and illegal trade in wildlife species used as pets or for decorative purposes threatens some species with extinction.

Overexploitation

Rhinoceros are often killed for their horns and sold illegally on the black market for decorative and medicinal purposes.

Overexploitation Case Study: Rising Demand for Bushmeat in Africa

Bushmeat hunting has caused the local extinction of many animals in West Africa.

Can spread disease such as HIV/AIDS and ebola virus.