8.2 Human Impacts on Ecosystems

Habitat loss and disruption

Human activities like deforestation, urbanization, and agriculture destroy or fragment habitats, reducing biodiversity. Habitat fragmentation splits ecosystems into smaller patches, isolating populations and reducing genetic diversity. Edge effects increase, altering microclimates and making species more vulnerable to predators, disease, and invasive species along habitat boundaries.

Invasive species and their impacts

Invasive species are non-native organisms introduced (often by humans) that spread rapidly and harm ecosystems by outcompeting native species for resources, lacking natural predators, or introducing disease. They reduce biodiversity, disrupt food webs, and can cause economic damage. Examples include zebra mussels and kudzu, which alter habitats and outcompete native species.

Overexploitation and pollution effects

Overexploitation — overharvesting, overfishing, and overhunting — depletes populations faster than they can reproduce, sometimes causing extinction. Pollution (chemical runoff, plastics, oil spills) contaminates air, water, and soil, harming organisms directly or through bioaccumulation/biomagnification up food chains. Combined, these human impacts degrade ecosystem services and reduce overall resilience.

Key terms

Habitat fragmentation

The division of a large habitat into smaller, isolated patches, reducing biodiversity and genetic diversity.

Invasive species

A non-native organism that spreads rapidly, often lacking predators, and disrupts native ecosystems.

Overexploitation

Harvesting a resource (fish, wildlife, timber) faster than it can naturally replenish, risking population decline or extinction.

Bioaccumulation

The buildup of a toxin or chemical within an individual organism over time.

Biomagnification

The increasing concentration of a toxin at each successive trophic level in a food chain.

Try an AP-style question

What is habitat fragmentation?

1. Restoring a damaged ecosystem
2. Merging two separate ecosystems
3. Species migrating each season
4. Breaking habitat into isolated patches