Chapter 13.                                

BIODIVERSITY

What is biodiversity?

The total genetic, species and ecological varieties of organisms found in a given area.

This includes all genetic variants of a single species, and the whole array of species in an area.

It includes the variety of ecosystems with its communities within particular habitats.

• Genetic diversity: different  versions of the same gene.
• Species diversity: number of different kinds of organisms in a locality.
• Ecological diversity: richness and complexity of the community, e. g. number of niches, trophic levels, recycling processes, etc.

 

What is a species?

A population of similar organisms that can produce fertile offspring without human intervention.

• In the wild.
• Rampant genetic exchange between members.

 

Reproductive isolation is the idea used in this definition.

Hybrids occur in nature and sometimes produce fertile offspring.

There are debates between taxonomists on the species status of many organisms.

DNA sequencing technology is helping to understand better the evolutionary relationship between species.

Number of species

We know about 2.1 million species.

The estimate of the total number of species in the world ranges from 3 million to 50 million.

                                               Identified                    Estimated

Bacteria                                   5,800                          10,000
Fungi                                       80,000                         1,500,000
Invertebrates                           1,500,000                    up to 50,000,000
Fish                                         20,000                         23,000
Birds                                       9,100                          9,200
Mammals                                4200                           4300
Plants                                      250,000                       300,000

 

The tropics are the centers of the greatest biodiversity.

 

BENEFITS OF BIODIVERSITY

1) FOOD

• As many as 80,000 wild plants are edible.

• Few plants used by ethnic minorities in the tropics have been studied for their food potential.

 

• These little known crops are a source of genetic material to improve domestic crops.

2) DRUGS AND MEDICINE

• About 90% of our medicines come from plants, bacteria and fungi directly or are derived from them.

 

• More than 50% of prescribed drugs contain some natural product.

• Pharmaceutical companies are actively investigating the useful natural products of tropical plants.

 

• Pharmaceutical products derived from the developing world plants, animals, bacteria and fungi amounts to $300 billion/year.

 

3) ECOLOGICAL BENEFITS

• Human life is inextricably linked to ecological services provided by other organisms.

 

• Soil formation, nutrient recycling, waste disposal, air and water purification, solar energy absorption, chemical cycles, pest control, etc. depend on organisms.

• Diverse communities are more stable and withstand stress better than less diverse communities.

 

• Nature maintains ecological processes at no cost for us and contains a genetic library of information that we could not reproduce.

• It is estimated that 95% of the potential pests and disease-carrying organisms are controlled by other species that prey upon them.

 

4) AESTHETIC AND CULTURAL BENEFITS

• Quality of life: recreation, beauty.

 

• Contact with nature could be psychologically and emotionally restorative.

• In some cultures, nature carries spiritual connotations, and a particular species or landscape may be inextricably linked to a sense of identity and meaning.

 

• For some, simply knowing that a particular species exists is reason enough to protect it and preserve it. This is called existence value.

THREATS TO BIODIVERSITY

 

Extinction is the elimination of a species.

Natural causes of extinction.

Over 99% of the species that ever existed are now extinct.

Periodically, mass extinctions have wiped out entire families of organisms, e.g. the dinosaurs at the end of the Cretaceous, 65 million years ago.

During the Permian, 250 million years ago, two thirds of all marine species and about half of  all plant and animal families died out in a period of about 10,000 years!

Human impact has accelerate the rate of extinction in the 20th century.

Species either die out or are replaced through evolution.

Evolution can occur at a slow or fast pace.

 

Human-caused reduction of biodiversity.

• Habitat destruction. The biggest  reason for the current increase in extinction.

 

• Hunting and fishing, e.g. the passenger pigeon, bison and several species of whale.

• Commercial products and live specimens. Trade of exotic animals and their products have brought some species to the brink of extinction, e.g. macaws, black rhinos.

 

• Predator and pest control. Some species have been hunted because they are considered dangerous to humans or livestock, e.g. reintroduction of the gray wolf controversy.

• Introduction of exotic species compete and eliminate native species, e.g. kudzu, Asian tiger mosquito transmits the West Nile virus, deadly to many birds.

 

• Diseases introduced from abroad can eliminate native species that lack the resistance to deal with the pathogen, e.g. American chestnut, American elm blight.

• Pollution. Pesticides and fertilizers have disastrous effects on organisms.

 

• Genetic assimilation by related opportunistic species.

 

ENDANGERED SPECIES MANAGEMENT

1) Hunting and fishing laws.

• To protect human future resources.
• To preserve game animals

 

2) Endangered Species Act.

• Established in 1973.
• To preserve biodiversity regardless of its usefulness to humans, a new approach to wildlife.
• Endangered are those near extinction
• Threatened are likely to become endangered at least locally.
• Vulnerable are those species that are rare and can easily become threatened or endangered.
• EAS regulates activities involving endangered species; it includes a wide range of activities: taking, harassing, shooting, harming, etc.; possessing; exporting, transporting, shipping, etc.
• In 1995 the Supreme Court ruled that habitat essential for an endangered species survival, must be protected whether on public or private land.
• United States has 1530 species on the endangered or threatened list.
• Expired in 1992.
• In 1995, the Supreme Court ruled that critical habitat (habitat essential of a species' survival) must be protected whether on public or private land.

 

3) Recovery plans of listed species.

• Prepared by the Fish and Wildlife Service detailing how populations will be rebuilt to sustainable levels.

 

• It often takes years to reach an agreement on a specific recovery plan.

• Major difficulties are cost, politics, and interference on local economic interests.

 

• Preserving the habitat of the species is a major source of debate, e.g. spotted owl and lumber companies; Tellico dam and the snail darter in Tennessee, 1978.

• The total cost of recovery plans for all currently listed species is estimated to be nearly $5 billion.

 

• Most of the money for protection and recovery, $150 million, goes to protect ten species.

 

4) Private land and critical habitat.

• Most of the habitat (80%) for listed species is on private land.

 

• Landowners do not want to be told how to use their property.

• Habitat conservation plans (HCP) are negotiated between the Fish and Wildlife Service and landowners.

 

• Under HCP plans, landowners are allowed to harvest resources or build on part of their land as long as the species benefits overall.

• Resistance where there is a potential economic benefit for the landowner.

 

5) Reauthorizing the Endangered Species Act.

• Expired in 1992.

 

• Congress has debated many alternatives from eliminating it altogether to strengthening it.

• It places the welfare of plants and animals above humans.

 

• Essential to maintaining the viability of the planet.

A very divisive issue. Two main points of view:

• Habitat protection and places a deadline for listing a recovery plan; it requires that HCPs do not negatively impact the species, and that it should be reviewed by an independent team of scientists.

 

• Vested interests should be included; the least costly and burdensome measures would be taken; Federal agencies will do self-consultation and avoid dealing with the Fish and Wildlife Service.

6) Minimum viable populations.

A species composed of very few individuals can undergo catastrophic declines due to environmental changes, genetic problems and random events.

Species found on islands located near continents and large islands are less susceptible than those found on small and oceanic islands.

Loss of genetic diversity due to fewer numbers limits adaptability, reproduction and survival.

Diversity is lost in small populations.

• Founder effect, when a few individuals establish a new population.
• Demographic bottleneck arises when only a few individuals survive a catastrophe.
• Genetic drift due to uneven reproductive success.
• Interbreeding.

 

7) Habitat protection.

• We are expanding our concern from individual species to protecting habitat and entire biogeographical regions.

 

• Many scientists and environmentalist support a continent-wide protection of ecosystems that support a maximum biological diversity.

• Gaps between protected areas may contain more endangered species than are preserved within the protected areas.

 

• Gap analysis is the study of unprotected landscapes that are rich in species: computer and geographical information systems allows the analysis of vast amount of data.

• The emphasis is biodiversity rather than on protection of one single rare species.

 

• Principles for protecting biodiversity in a large scale, long range approach:

• Protect enough habitat for viable populations of all native species in a given region.

 

• Manage at regional scale large enough to accommodate natural disturbances (fire, wind, etc.)

• Plan over a period of centuries so that species and ecosystems may continue to evolve.

 

• Allow for human use and occupancy at levels that do not result in significant ecological degradation.

 

8) International wildlife treaties.

• Convention on International Trade in Endangered Species (CITES) was established in 1975.

 

• It regulates trade in living specimens and products derived from listed species.

• Investigation and enforcement are especially difficult in developing countries where wildlife is disappearing most rapidly.

 

• Appendix I of CITES lists 700 species threatened with extinction by international trade.

 

ZOOS, BOTANICAL GARDENS AND CAPTIVE BREEDING PROGRAMS.

Zoos and botanical gardens are entertaining and educational.

Most mammals in U.S. zoos are produced now by captive breeding programs. Some species rarely breed in captivity.

There are limits to the number of captive species we could maintain under captive conditions.

The genealogy of the animal is kept in a database at the Minnesota zoo.

Botanical gardens and research institutions are repositories for rare and endangered plant species that sometimes have ceased to exists in the wild.

 

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