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August 2012
Environmental Science Ch # 11
Biodiversity
11 -1. Biodiversity Issues. Biodiversity is described in terms of Genes, Species and Ecosystems. Its loss
results from Extinction and Human Domination. Extinction is normal.
Cause of Extinction is primarily due to Habitat Destruction. Most likely to become extinct are those
animals with: Small populations, Restricted habitats, Specialized, Low rates of reproduction, and which
feed at higher trophic levels
Extinction due to human activities, such as:
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Modification of the ecosystem to benefit man, leads to displaced organisms.
Killing for food.
11-2 Describing Biodiversity
Genetic diversity. In a society with many different individuals, structures and abilities, there is a high
biodiversity. The factors which influence genetic biodiversity are:
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Mutations – modifying genes already present
Migration – entering another population. Increasing numbers
Sexual reproduction – new combinations
Population size – smaller populations have less diversity
Selective breeding – eliminate some characteristics.
Species diversity is a measurement of the number of species present in an area. They are influenced by:
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Evolutionary and geologic history of the region
Climate change
Migration
Area size
Human activity such as: converting biomes , introducing species (Nelgay) , killing species.
Ecosystem diversity is a measure of the number of ecosystems in the region. That is a function of “local
regions” – microhabitats – (Climate, topo, vegetation.).
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Value of Biodiversity.
Value can be assigned after we understand an Organism role, its economic impact and take into
consideration ethical considerations.
Organisms’ role. ( Biological and Ecosystem Services Values). Services provided by the
ecosystem must be assigned a $ value, because each organism is interdependent on others. When
decisions are to be made, services are not to be overlooked. Example: Trees clean the air, produce food
on which we depend. If trees are allowed to become extinct, genes are lost.
Direct Economic Values. ( Agriculture, forestry and fisheries) in undeveloped countries, income
may never enter the formal economy. Services may have significant value. For example: Nutrient cycling
done by Nitrogen fixing bacteria; Cultural uses; water regulations and supply; disturbance regulations
and soil erosion; waste treatment; food and raw materials; Atmospheric and climate services;
Recreation; Biological Control services and soil formation.
Ethical Values. All species have an intrinsic value and a fundamental right to life, without being
needlessly eliminated. One’s values are developed as a result of experiences.
Threats to Biodiversity.
The value of an exploited resource can be measured in economic terms, but not so for the preservation
of biodiversity.
Human threats to biodiversity result from:
Habitat loss – conversion to agriculture; Conversion to Agriculture alters the biotic nature of an
area. As human population increases, space requirements increase.
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Forestry practices in deforestation – Forested areas change climate, reduces run off, protect
against soil erosion, silt accumulation in streams, water temp. lowered, less hunting .
Logging practices are clear cutting, patch work clear cutting, and selective harvesting.
Concerns about tropical deforestation.
Here is the largest biodiversity of all terrestrial biomes. It requires harvesting techniques significantly
different from those used in temperate forests.
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Harvesting large tracks reduce biodiversity, alters climate and affects global warming. It is a
Carbon Sink.
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Plantation forestry – single species , hybrid is planted. It is fast growing but does not support
diverse wild life.
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Range land and grazing practices in a region too arid to support agriculture. Used to raise
domesticated animals. Has a major impact on biodiversity. Indigenous plants are removed
and animals driven off. Overgrazing and harvesting fuel wood leads to desertification.
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Habitat loss in an aquatic Ecosystem. – Shallow water, marine bottom dwellers are
harvested, 25% of which have no commercial value. Rivers and lakes are dammed , which
prevents up stream migration .
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Conversion to Urban and Industrial usage. 4.3% /year natural ecosystems are destroyed.
Trend is towards urbanization.
Over exploitation is responsible for 30% endangered species, 8% plants.
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Poaching nets $ 2 to 30 Billion /year
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Overfishing – 70% marine fishing grounds are over exploited. Reduced catches have caused
the sale of previously regarded unacceptable fish.
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Aquaculture causes pollution, possible genetic alteration. It is becoming an increasingly
important food source. 60% salmon sold is farmed.
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Unsustainable harvesting of wild life and plants – Bush meat used for food and as a source
of income.
Introduction of Exotic species, accidental or deliberate. Results in the native species die off.
Diseases change the nature of the forest. Can be controlled by destroying infected trees
Control of pest organisms. i.e the systematic killing of predators as Passenger pigeons or Bald Eagles.
Climate change may affect amphibians, corals and Arctic species.
11 – 4. WHAT IS BEING DONE TO PRESERVE BIODIVERSITY ?
Legal Protection – Treaties (Biodiversity treaties 168 of 191 nations signed). Habitats
established Legislation (Endangered species Act).
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Legislation . set up a classification as: Endangered (unlikely to survive). Vulnerable
(decreasing population). Rare (Small population worldwide). Indeterminate (believed to be
endangered).
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Education programs.
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Purchase of sensitive habitats.
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Sustainable management of Wild life populations; requires habitat analysis and
management (Cover, food, protection); Population assessment (Carrying Capacity and
hunting); Special issues concerning migratory birds and animals.
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Sustainable Management of Fish Populations – whose habitat is shallow waters. 200
Nautical miles. Claimed 300 Km. Designate non-fishing areas. Presently researching the best
fishing methods.
EEZ is 350km. .