Answers to Review Questions
1. The principal threats to biodiversity are habitat loss, degradation, and fragmentation; the spread of invasive species; overharvesting; and climate change. For some species, disease poses a threat, and for others, particularly aquatic species, pollution is a particular threat.
Many freshwater mussel species of North America are threatened both by pollution and by the invasion of the zebra mussel. The Pyrenean ibex was driven extinct by hunting, climate change, disease, and competition with domesticated species. Many other examples are possible.2. DNA profiling (see Ecological Toolkit 23.1) and other genetic analyses are used to understand and manage genetic diversity in rare species; genetic approaches are also used in forensic studies of illegally harvested organisms. Conservation biologists use population viability analysis (PVA) models to assess extinction risk and evaluate options for managing rare species. Finally, ex situ conservation can be used to rescue species on the brink of extinction, as illustrated by ongoing efforts to protect the California condor.
3. The classification system set up by Natural Heritage/NatureServe documents each species' conservation status from a biological perspective, while a listing under the U.S. Endangered Species Act is a legal designation. While federally endangered species would generally also be considered globally rare by Natural Heritage/NatureServe, the reverse does not necessarily hold true: many extremely rare or threatened species are not on the federal endangered species list. The Endangered Species Act (ESA) provides legal protection for listed species, and it requires the designation of critical habitat and the development and implementation of a recovery plan for those species. In contrast, Natural Heritage/NatureServe can only recommend the protection of species.
4. Answers to this question will depend on where students are located and what species they identify. The objective of this question is to make students aware of species of conservation concern, threats to biodiversity, and efforts that are under way to protect species in their own region. It also invites them to identify research needs and to think about scientific approaches to conservation.