ENVS200-wk4.1-biodiversity1

Biodiversity and Populations

• Course: ENVS 200

Student Learning Objectives

• Students will learn to:

  • Explain types of extinction and human impact on extinction rates.

  • Define speciation and its natural processes.

  • List human efforts to protect wild species.

  • Understand invasive species and their associated issues.

Keystone Species

• Definition: Vital for defining an ecosystem; its absence leads to significant ecosystem changes.

• Characteristics:

  • Low functional redundancy, meaning no other species can replace its role.

  • Strong influence on food web dynamics.

• Example:

  • The wolf in the Yellowstone ecosystem.

    • ~90% of prey is elk, ~10% is deer.

The Role of Keystone Species in Yellowstone

• Historical Context:

  • Yellowstone became a national park in 1827.

  • Government eradication efforts led to the last wolf pups being killed in 1924.

• Impact of Removal:

  • Caused a trophic cascade in the ecosystem.

  • Resulted in:

    • Elk population explosion.

    • Overgrazing leading to stressed herbivores.

    • Stream bank erosion and increased water temperatures.

Recovery Efforts for Wolves in Yellowstone

• 1973: Wolves were listed as an endangered species.

• Yellowstone designated as a recovery area; 41 wolves were released between 1995-1997.

• Current status (January 2023): 108 wolves across 10 packs.

Ecosystem Responses to Environmental Changes

• Ecosystems change species composition in response to environmental shifts.

• Ecological Succession:

  • Gradual species composition changes over time.

  • Presents two types:

    • Primary Succession:

      • Occurs in lifeless areas without soil (terrestrial) or sediment (aquatic).

      • Duration: hundreds to thousands of years.

    • Secondary Succession:

      • Happened post-disturbance where soil remains, enriching biodiversity.

Speciation: How New Species Arise

• Definition: Creation of new species, splitting from a parent species that cannot breed successfully with it.

• Common Paths:

  • Geographic Isolation:

    • Populations become physically separated over time leading to distinct species.

  • Reproductive Isolation:

    • Related species cannot breed due to barriers, resulting in sterile offspring (e.g., horse and donkey producing a mule).

Consequences of Species Under Crisis

• Possible outcomes for endangered species:

  • Adaptation to environmental changes.

  • Migration to suitable habitats.

  • Extinction.

Extinction Details

• Extinction: total disappearance of a species (biological extinction).

• Natural Extinctions:

  • Background extinction rate reflects a slow, ongoing loss of species.

  • Mass Extinction:

    • A significant rise in extinction rates; at least 75% of species extinct within a few million years.

• Historical Mass Extinctions:

  • Five notable mass extinctions; biodiversity tends to recover significantly following these events.

    • Notable events include End Permian (250 Mya) and End Cretaceous (65 Mya).

• Current extinction rates driven by human activity—predicted to rise significantly in the next century.

Major Causes of Extinction

• Include:

  • Habitat loss.

  • Climate change.

  • Invasive species.

  • Pollution and overexploitation (poaching).

The Threat of Non-Native Species

• % of U.S. endangered species linked to non-native species.

• Examples of invasive species:

  • Argentinean fire ants, Kudzu, Zebra mussels.

• Management Strategies:

  • Prevention, research, and satellite monitoring for predicting impacts.

Action Steps for Conservation

• International treaties to control species transfer.

• Public education on the risks of non-native species.

• Proactive laws like the Endangered Species Act of 1973.

Balancing Conservation Efforts

• Need to allocate limited resources between protecting species and ecosystems.

• Consideration of which species to protect based on threat level and ecological significance.

• Avoid consumption of products derived from threatened species to reduce market demand.

The Road Ahead

• 25-50% of currently identified species could be extinct by the end of the century due to human activities.

• Emphasis on the importance of protecting keystone species to maintain ecosystem services.