9.9 Endangered Species

What makes a species endangered

An endangered species is one at serious risk of extinction, usually due to human activities. A threatened species is likely to become endangered soon. Main causes include habitat destruction/fragmentation, pollution, climate change, overharvesting, and invasive species (HIPPCO). Small populations are especially vulnerable due to reduced genetic diversity, making them less able to adapt to environmental change.

Measuring biodiversity loss

Conservationists track species using tools like the IUCN Red List, which categorizes species from least concern to extinct. Loss of a species can trigger a trophic cascade, disrupting food webs and ecosystem services. Keystone species and indicator species are especially important to monitor, since their decline signals broader ecosystem stress.

Protecting endangered species

Legal protections like the U.S. Endangered Species Act (ESA) and international agreements like CITES (Convention on International Trade in Endangered Species) regulate trade and protect habitats. Conservation strategies include captive breeding programs, wildlife refuges/corridors, and habitat restoration. Protecting biodiversity preserves genetic resources, ecosystem services, and resilience for the future.

Key terms

Endangered species

A species at serious risk of extinction due to human or natural causes.

HIPPCO

Habitat destruction, Invasive species, Population growth, Pollution, Climate change, Overharvesting — major causes of biodiversity loss.

IUCN Red List

An international database that categorizes species by their risk of extinction.

CITES

Convention on International Trade in Endangered Species — regulates global wildlife trade to protect vulnerable species.

Captive breeding program

A conservation method that breeds endangered species in controlled settings to increase population size, sometimes for reintroduction into the wild.

Try an AP-style question

What is the leading cause of species endangerment?

1. Habitat loss
2. Light pollution
3. Ecotourism
4. Noise pollution