Visualizing Environmental Science

394 CHAPTER 15 Biodiversity and Conservation

2. An endangered species is a species that faces threats
   that may cause it to become extinct within a short period.
   A species is defined as threatened when extinction is less
   imminent but its population is quite low.


3. Humans cause species endangerment through habitat
   destruction, fragmentation, and degradation; pollution;
   the spread of invasive species; and the overexploitation of
   biological resources. Endemic species are organisms that
   are native to or confined to a specific place. Biodiversity
   hotspots are areas that contain particularly high numbers of
   endemic species. Invasive species are foreign species, usually
   introduced by humans, that spread rapidly in a new area where
   they are free of predators, parasites, or resource limitations
   that may have controlled their population in their native habitat.

3

Conservation Biology 386

1. Conservation biology is the scientific study of how humans
   affect organisms and of the development of ways to
   protect biological diversity. In situ conservation includes
   the establishment of parks and reserves to preserve
   biological diversity in nature; ex situ conservation involves
   conservation of biological diversity in human-controlled
   settings such as zoos and seed banks.


2. Restoration ecology is the study of the historical condition of
   a human-damaged ecosystem, with the goal of returning it as
   closely as possible to its former state.

4

Conservation Policies and Laws 390

1. The Endangered Species Act (ESA) authorizes the U.S.
   Fish and Wildlife Service (FWS) to protect endangered and
   threatened species in the United States and abroad. The
   ESA requires the FWS to select critical habitats and design
   a detailed recovery plan for each species listed. Species
   are designated as endangered or threatened entirely on
   biological grounds, not economic factors. The act does not
   compensate private property owners who suffer financial
   losses related to its enforcement.


2. The World Conservation Strategy, formulated by the
   International Union for the Conservation of Nature, the World
   Wildlife Fund, and the U.N. Environment Programme, seeks
   to conserve biological diversity worldwide, to preserve vital
   ecosystem services, and to develop sustainable uses of
   organisms and their ecosystems.

Summary

1

Species Richness and Biological

Diversity 374

1. Species richness is the number of different species in
   a community. High species richness is associated with
   communities that are ecologically complex, not isolated,
   geologically old and stable, and not subject to environmental
   stress. Species richness is also higher when no one species
   dominates the community.


2. Biological diversity is the number and variety of Earth’s
   organisms; it consists of three components: genetic diversity,
   species richness, and ecosystem diversity. Genetic diversity
   is the genetic variety within all populations of a given species.
   Ecosystem diversity is the variety of interactions among
   organisms in natural communities.


3. Ecosystems with greater species richness are better able to
   supply ecosystem services: environmental benefits such as
   clean air to breathe, clean water to drink, and fertile soil in
   which to grow crops.

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Endangered and Extinct Species 378

1. Extinction is the elimination of a species from Earth.
   Background extinction, a continuous, low-level extinction
   of species, has occurred throughout Earth’s history. Mass
   extinction, in which many species disappear during a
   relatively short period of geologic time, has occurred only a
   few times in Earth’s history.

✓✓THE PLANNER

Human population

increase

Land-use

change

(habitat loss)

Climate

change

Pollution

Overexploitation

(for example,

overfishing)

Invasive

species

Increasing

economic

activity

Increased

use of

technology

Declining

biological

diversity

Social, political, and

cultural factors