Human Disturbances to Ecosystems Sustaining Biodiversity

The Passenger Pigeon: Gone Forever Once 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 Species: 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 Extinction A. 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 Extinction Some species have characteristics that make them vulnerable to ecological and biological extinction.

II. 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 Republic

II. Species Extinction C. 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 biodiversity When area to live is gone, organisms die Why would the habitats go away? Ex. deforestation

Habitat Fragmentation Separation of wilderness areas from other wilderness areas Fragmented 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) Species New 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 Species Many 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 southeastern U.S. to control erosion. It has taken over native species habitats.

Invasive Species Many invasive species have been introduced intentionally.

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

Population 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 environment Different levels of consumption and numbers of people drive tensions between countries

Figure 55.0 Deforestation of tropical forests

P. Pollution Damage to habitat by pollution Three types of pollution: ◦ Air ◦ Water ◦ Land

O. Overexploitation Some 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.