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Enger & Smith
Environmental ScienceA Study of Interrelationships
Thirteenth Edition
Chapter 11
Biodiversity Issues
Biodiversity Issues
11.1 Biodiversity Loss and Extinction
Biodiversity• diversity of genes,
species, and ecosystems in a region.
Extinction is the elimination of all the individuals of a particular species.
• Natural and common event in the history of biological evolution.
• Major consequence of human domination of the Earth.
– humans increased the extinction rate 1,000 to 10,000 times above background rates
11.1 Biodiversity Loss and Extinction
Kinds of organisms prone to extinction
Local extinctions• Species may not have a future
Some genetic diversity lost.• As population is reduced in size
Certain kinds of species are more likely to go extinct than others:• Species with small, dispersed populations
– Successful breeding is difficult.
11.1 Biodiversity Loss and Extinction
• Organisms in small, restricted areas, such as islands.– Environmental changes have large effect.
• Specialized organisms– Relying on constancy of a few key factors.
• Organisms at higher trophic levels.– Low population sizes and reproductive rates.
11.1 Biodiversity Loss and Extinction
We are dependent on the diversity of organisms• Services provided by ecosystems/organisms
Nutrient Cycling• Carbon, nitrogen, phosphorus• cycled through ecosystems
Cultural Uses• Enjoyment of landscapes, scientific study• Educational activities, spiritual significance of places
11.2 The Value of Biodiversity
11.2 The Value of Biodiversity
Water regulation and supply• Intact soil and vegetation slow water flow
• Water penetrate soil to recharge aquifers• Water available for agriculture, industry, and domestic
use.
11.2 The Value of Biodiversity
Disturbance regulation and erosion control• Land disturbed by fire, flood, windstorms, landslides,
or human actions.• Plants and animals heals the scars and prevents
continued damage.
Waste Treatment• Decomposer organisms remove excess nutrients and
pollutants from air, water, and soil.
11.2 The Value of Biodiversity
Food and Raw Materials• Harvest wild plants and animals as food and
medicine. • Plants feed livestock, provide building materials, and
firewood.
Atmospheric and Climate Services– Removal of carbon dioxide in photosynthesis helps
control the warming of the planet.– Nitrogen and sulfur are modified by organisms.– Ozone provides protection from UV light.
11.2 The Value of Biodiversity
Recreation• Natural areas provide recreational opportunities.
Biological Control Services• All organisms have complex interrelationships. Some
help remove pests.
11.2 The Value of Biodiversity
Pollination Services• insects are pollinators. • Insecticides can negatively affect agricultural
production.
Habitat/Refuges• Protect species• nursery sites• temporary stopping places for migratory species.
18 miles N Omaha
11.2 The Value of Biodiversity
Genetic Resources• If organism goes extinct
– lost the ability to use it for our own needs.
• 50% of our common drugs come from plants and animals.
Soil Formation• Weathering of rock builds soil
– aided by bacteria, fungi, tiny animals, and plants roots – Food supply depends on protection and management of
soil.
11.2 The Value of Biodiversity
Approximate values• 33.3 trillion (1997)• 50 trillion
• Agriculture (670 billion)
• Forestry (200 billion)
• Fisheries (80 billion)
11.2 The Value of Biodiversity
A case can be made that all species have an intrinsic value and a fundamental right to exist.• Extinction is not necessarily bad, but human-initiated
extinction is.• Experiencing natural landscapes and processes is an
important human right.
Threats caused by Humans
Five major human activities threaten to reduce biodiversity.• Habitat loss• Overexploitation
• Introduction of exotic species
• Predator and pest control activities
• Climate change
11.3 Threats to Biodiversity
Habitat Loss• Human activities
– Convert natural ecosystems to human-dominated
– Farming, forestry, grazing
(IUCN) • 80%-90% of threatened species are under threat
• habitat loss or fragmentation– major cause of past extinctions.
11.3 Threats to Biodiversity
40% of the world’s land surface • converted to cropland and permanent pasture.
Most productive natural ecosystems • (forests and grasslands) are the • first to be modified by humans.
Pressure to Modify the environment • greatest in areas with high population density.
11.3 Threats to Biodiversity
Historical forests• ½ of U.S., ¾ Canada; most of Europe
Deforestation • process of destroying a forest, • often for the purposes of fuel, building materials, or to
clear land for farming.
11.3 Threats to Biodiversity
Changes in forest area
11.3 Threats to Biodiversity
Modern forest management practices • compromise • allows economic exploitation while maintaining some
environmental values of the forest
• Logging– Selective– Shifts species diversity
Forestry Practices• Forested areas effectively:
– Habitat for plants/animals
– Reduce erosion.
– Reduce runoff.
– Modify the climate.
– Provide recreational opportunities.
Marsupial-the Numbat
11.3 Threats to Biodiversity
Clear cutting • removal of all trees in
an area• economical but
increases erosion– especially on steep slopes
Forest Harvesting Methods
Patchwork clear cutting • Use of sites with steep slopes• clear cutting in small, unconnected patches;• preserves biodiversity.
Selective harvesting • single species tree harvesting
• not as economical
• reduces ecosystem damage.
11.3 Threats to Biodiversity
Tropical forests • greater species
diversity than any other ecosystem
• not as likely as temperate forests to regenerate
• poor soil characteristics.
11.3 Threats to Biodiversity
Tropical deforestation:• Reduces species diversity in the world.
• Impacts the climate via lowered transpiration.
• Deforested lands are easily eroded.
• Without the forests to trap CO2, there may be increased global warming.
11.3 Threats to Biodiversity
Rangelands • lands too dry to support crops• receive enough precipitation to support grasses and
drought-resistant shrubs
Raise livestock
Wildlife are usually introduced species not native to the region.
11.3 Threats to Biodiversity
Use of rangelands
11.3 Threats to Biodiversity Conversion of rangelands to grazing
• Major impacts on biodiversity.
• Eating habits of livestock – reduce certain species of native plants and encourage others.
• Regulate number of livestock on rangelands, especially in dry areas.
– Overgrazing
– Desertification--converting arid or semiarid land to desert because of improper human use.
11.3 Threats to Biodiversity
Desertification
11.3 Threats to Biodiversity
In marine ecosystems, • Harvest is restricted to shallow parts of the ocean• bottom-dwelling fish can be easily harvested.
Trawls are nets dragged along the bottom. • disturb the seafloor and cause habitat damage.
25% of catch is discarded• dead
• further alters the ecological nature of the seafloor.
Habitat Loss in Aquatic Ecosystems Freshwater systems
• modified for navigation, irrigation, flood control, or power production.
Threats caused by Humans: Overexploitation
Overexploitation is responsible • 30% of endangered animal species • 8% of endangered plant species.
• Overexploitation occurs – when humans harvest organisms faster than the
organisms are able to reproduce– threatening some, and causing extinction in others.
11.3 Threats to Biodiversity
70% of world’s marine fisheries • overexploited or
• fully exploited and in danger of being overexploited
• Sign of overexploitation
– Marketing fish that once were “unacceptable”
11.3 Threats to Biodiversity
Fish farming (aquaculture) • important as a source of fish production.
60% of all aquaculture production is from freshwater systems.
The environmental impacts • Nutrient overloads
• Escape into natural waters• Land conversion
11.3 Threats to Biodiversity: Unsustainable harvesting
Meat from wild animals is often referred to as bush meat.• 70% of wildlife species in Asia and Africa • 40% of species in Latin America are being hunted
unsustainably.• Part of all subsistence cultures.
• Delicacies and are highly prized for the home and restaurant trade.
11.3 Threats to Biodiversity Pet and aquarium trade
• The method of capture is often problematic.– Destruction of bird nests.– Toxins used to stun fish.
Parts of the animal have particular value.– Ivory and animal skins– Traditional medicines
11.3 Threats to Biodiversity: Control of Predators and Pests
Systematic killing • certain organisms that interfere with human activities
• Large predators have been locally exterminated because they preyed on domestic animals.
• Control pests (cowbird) is
helping
11.3 Threats to Biodiversity The role of climate change, survival of species
• Many species live near the limit of their physiological tolerance.
– slight change in the temperature may push them over the brink.
• Amphibians, corals, and arctic species are greatly affected by climate change.
– Planet warming may have caused a fungal disease in frogs.
– Melting sea ice is changing migration patterns and food availability.
11.3 Threats to Biodiversity
11.4 What Is Being Done to Preserve Biodiversity?
The World Conservation Union (IUCN) lists over 16,000 species as threatened with extinction.• IUCN classifies species in danger of extinction into four
categories:– Endangered– Vulnerable
– Rare
– Indeterminate
11.4 What Is Being Done to Preserve Biodiversity?
In the U.S., • Endangered Species Act (1973).• Designates species as endangered or threatened and • Gives the U.S. government jurisdiction over those
species.
• No activity by a government agency should lead to the extinction of an endangered species.
• Government agencies to use whatever means necessary to preserve the species in question.
11.4 What Is Being Done to Preserve Biodiversity?
Endangered species • small numbers that they are in immediate danger of
becoming extinct.
Threatened species • could become extinct if a critical environmental factor
is changed.• 1/8 of bird species, 1/4 of mammal species, 1/3 of
amphibian species, and 1/2 of turtle species are threatened.
11.4 What Is Being Done to Preserve Biodiversity?
Habitat Analysis and Management• Managing a particular species
• Understanding of the habitat needs of that species.– habitat must provide food, water, and cover.
• Modifications made to enhance the success of a species are known as habitat management.
11.4 What Is Being Done to Preserve Biodiversity?
Wildlife management • harvesting for sport and meat• Important population management technique.• managed so they do not exceed carrying capacity of
their habitat.
When populations get too small, artificial introductions can be implemented.• Native species can be reintroduced to areas where
they had been extinct.
11.4 What Is Being Done to Preserve Biodiversity?
Managing a wildlife population
11.4 What Is Being Done to Preserve Biodiversity?
Coastal regions are most productive regions of the oceans. • Sunlight penetration of shallow water makes it warm.• Nutrient deposition from land makes this region fertile.• Fishing pressure is concentrated here.
Management of marine fisheries • achieving agreement on harvest limits
Summary
Loss of biodiversity has become a major concern. Ecosystems involve the interactions of organisms
and their physical environment. Functioning ecosystems and their component
organisms provide many valuable services that are often overlooked because they are not easily measured in economic terms.
Summary
Many people also consider the loss of biodiversity to be an ethical problem.
The primary causes of habitat loss are by:• Humans converting ecosystems to agriculture and
grazing.
• Overexploitation by harvesting species at unsustainable levels.
• Introduction of exotic species that disrupt ecosystems and compete or prey on native organisms.
• Purposeful killing of pest organisms such as large predators.
Summary
Protection of biodiversity typically involves legal protections by national laws and international agreements, and management of the use of species and ecosystems at sustainable levels.
