Invasive Species Notes

Definition of Invasive Species

  • Invasive Species: A species introduced to an ecosystem in an unnatural manner.

Ecosystem Dynamics

  • Ecosystems consist of living (biotic) and nonliving (abiotic) components that interact in a balanced way.

  • Change in ecosystem conditions (e.g., scarcity of food, temperature fluctuations) can force local/native species to adapt.

  • Quick alterations can overwhelm local species’ ability to adapt, leading to extinction.

Disruption Caused by Invasive Species

  • Introduction of invasive species creates significant disruptions:

    • They often arrive unintentionally (e.g., through shipping).

    • Sometimes brought intentionally by humans to solve ecological problems.

    • They frequently lack natural predators in their new environment, allowing them to dominate.

Examples of Invasive Species

Cane Toad (Rhinella marina)

  • Introduced: Australia in 1935 for pest control.

  • Impact: Rapidly multiplied and reduced native insect populations, impacting local food chains.

    • Currently, millions of cane toads threaten native wildlife due to their voracious appetite.

Kudzu (Pueraria montana var. lobata)

  • Introduced: In America in 1876 from Asia.

  • Impact: Grows rapidly (up to 1 foot/day) and covers trees, houses, and other structures, smothering native plants and disrupting local ecosystems.

Brown Tree Snake (Boiga irregularis)

  • Introduced: Guam in 1952, likely from shipping cargo.

  • Impact: Endangered local bird and lizard populations due to its predation, resulting in ecological imbalances.

Hydrilla (Hydrilla verticillata)

  • Introduced: 1950s into Florida after being discarded.

  • Impact: Forms dense mats in water bodies, choking out native aquatic species and resulting in biodiversity loss and costly management efforts.

Lionfish (Pterois volitans)

  • Introduced: Florida in 1992, origins unknown.

  • Impact: Rapid population growth disrupts local marine ecosystems, as they are voracious predators with few natural enemies in their new habitat.

Emerald Ash Borer (Agrilus planipennis)

  • Introduced: Michigan in 2002; means of introduction unclear.

  • Impact: Destroys ash trees and poses a threat to the timber industry and biodiversity of affected areas.

Effects of Invasive Species on Ecosystems

  1. Competition for Resources: Invasive species often outcompete native species for food, space, and light.

  2. Reduction of Biodiversity: By dominating ecosystems, they can lead to the decline or extinction of native species, ultimately reducing biodiversity.

  3. Economic Impact: Invasive species can impose significant costs related to management and loss of ecosystem services.

Importance of Biodiversity

  • Biodiversity contributes to ecosystem resilience, stability, and productivity, which are essential for maintaining healthy ecosystems.

Questions for Reflection

  1. What are three ways invasive species affect ecosystems?

  2. How do invasive species typically reduce biodiversity?

  3. Why is biodiversity critical to maintaining healthy ecosystems?

Argument Construction

  • Prepare argument discussing which invasive species had the largest ecological impact, supporting claims with evidence from the reading - engage in debate.