Geography 2412 Lecture Notes

Chap. 16: Biological Diversity

Species : physiologically similar organisms that can interbreed. (though biologist disagree on some definitions and arguments about whether a particular species is truly different then related ones somewhere else do arise in species protection policy. )

Biodiversiy is number of species in a geographical area or ecosystem (could be a measure, too, of global biodiversity). Globally:

– maybe 1.4 million identified;

– maybe 4 million extant

– 1 in 8 plants endangered

Biodiversity is a balance of speciation (emergence of new species) and species extinction or loss.

A human-caused extinction event is underway; started with post-Ice Age expansion of humans and improved hunting skills; then agricultural revolution and spread; then industrialization, with continued spread of ag and settlement especially in tropical forests, where biodiversity is high.

Characteristics that make Species Vulnerable:

• small range ("micro-endemic"): very small ranges subject to single, cataclysmic events (e.g., a hurricane, landslide, etc.) that wipe out the whole pop.
• small population / isolation ("island bio-geography"): there’s safety in numbers and ability to interact with other populations; isolation may even cause extinction as genetic drift degrades adaptability even without habitat change.
• narrow habitat needs, narrow food needs (pandas): puts the species at risk if anything happens to its food supply.
• sensitivities (condor eggs to DDT): some species more sensitive to pollutants than others, some rend to respond to toxics more or less well.
• non-adaptive behaviors: some species even those routinely hunted, seem unable to "learn" avoidance behaviors(e.g., whales); others are better at it (e.g., coyotes and grizzly bears).
• Poses threat to people and livelihoods (wolves): noxious or pest species are often targeted for extermination because they compete with us for food or space, and may even threaten humans.

Human Causes of Species Endangerment:

• Hunting/extermination: sport hunting not as big a problem with modern regulations, most sport hunters work to maintain the base of their prey, though a few less protected species in a few parts of world are still hunted for sport though they are near to extinction. Now problem is species that people consider a pest and that are hunted for extermination (e.g., prairie dogs).
• Pollution: (e.g., DDT and Condor eggs) pollutants that disrupt life-cycle or habitat.
• Agricultural and other forces for monocultures: selection for certain crops reduces biodiversity in indirect ways (e.g., reducing pollen rain), can also result from selection for certain decorative and pet species of plants and animals.
• introduced exotics: may out-compete or prey on the endemic species.
• global warming and other global-scale changes: changes habitat, perhaps faster than species can adapt or migrate. Changes disturbance regime (e.g., more or fewer wildfires)

Habitat loss is one main cause of endangerment

– Habitat: space and environmental elements that provide home to species

– Niche: functional role of species in habitat

– Theory of “island biogeography”: extinctions increase as habitat size decreases.

– Habitat fragmentation:

• Islands or patches

• Edges

• Corridors

Habitat: space and environmental elements that provide home to species

(Niche: functional role of species in habitat; predators play a role or niche, as do decomposers.)

Theory of "island biogeography": extinctions increase as habitat size decreases (see Fig. 16.7).

Habitat fragmentation: sometimes fragmentation can be more important than net loss of size (reduction) of total habitat, if remaining patches are cut-off from each other, then each acts as separate island of species, and each acts as an isolated, micro-endemic species. More at risk as their pop reduced in each patch.

Edges: species adapted to a certain habitat often do less well in that habitat near its edge (edge with another habitat), where the influences of the neighboring habitat may impinge (e.g., predators, competitive species, physical effects—e.g., if you need forest cover to survive, it often thins out at the end of a patch of forest).

Corridors: natural corridor link habitats and allow for migrations, either short-term (seasonal or even diurnal) or long term (e.g., in response to climate change).

Species Conservation:

Endangered Species Act (1973)

Act of congress requires federal agencies (US Fish and Wildlife Service takes lead) to assess and "List": Threatened (pop decline) and Endangered ("near extinction").

Regulations then make it illegal to "take" or harm species (capture, kill, ruin its last habitat); right now the act requires no economic considerations, that is: the species must be saved no matter what economic losses it causes. But now social and economic considerations are more frequently included in species management and protection, , and arguments have been made in congress to amend act to consider human needs, economic impacts.

Conservation:

• Protect species from “take” (see ESA below)

• Captive breeding/Re-introduce species to habitats

• Apply: Landscape Ecology

– Protect as much habitat as possible; integrated landscape management: cores. corridors, human activities.

– Protect large habitats and corridors for migration (reduce barriers) –reconnect habitat fragments

– Improve existing habitat quality; repair and recreate habitat (e.g., wetlands), extract exotics

Protect species from "take" (Endangered Species Act)—good, but does not address habitat and other vulnerabilities very well.

Protect as much habitat as possible; integrated landscape management: cores. corridors, human activities.

Protect large habitats and corridors for migration (reduce barriers) ---based on theory of island biogeography.

Improve existing habitat quality; repair and recreate habitat (e.g., wetlands)

Re-introduce species to habitats from which they have been removed.

Why Might We Conserve Species?

• Economic value of species and their habitats (medicines, industrial compounds, etc.)
• Value to agriculture and food systems from natural ecosystems: diverse germplasm to chose from for future hybrids/crops, maybe to obtain resistance to new forms of disease. Natural pollinators.
• Other "Ecosystem services": diverse ecosystem more stable, produce more reliable services (freshwater, flood protection, cleansing pollutants, etc.)
• Historical, esthetic and moral/spiritual reasons