Environmental crisis lecture 8

transcript

Enger & Smith

Environmental ScienceA Study of Interrelationships

Thirteenth Edition

Chapter 11

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

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.

• 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.

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

Water regulation and supply• Intact soil and vegetation slow water flow

• Water penetrate soil to recharge aquifers• Water available for agriculture, industry, and domestic

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.

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.

Recreation• Natural areas provide recreational opportunities.

Biological Control Services• All organisms have complex interrelationships. Some

help remove pests.

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

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

Approximate values• 33.3 trillion (1997)• 50 trillion

• Agriculture (670 billion)

• Forestry (200 billion)

• Fisheries (80 billion)

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.

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.

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.

Changes in forest area

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

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.

Tropical forests • greater species

diversity than any other ecosystem

• not as likely as temperate forests to regenerate

• poor soil characteristics.

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.

Discussion

http://www.youtube.com/watch?v=2OA7FB2vrMo

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.

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.

Desertification

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.

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”

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.

11.4 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

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.

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.

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.

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.

Managing a wildlife population

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.