Environmental crisis lecture 8

Environmental Science
A Study of Interrelationships
Thirteenth Edition

Enger & Smith

Chapter 11
Biodiversity Issues

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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.

11.2 The Value of Biodiversity
 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

 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.

 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.

 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.

 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

 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.

 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

 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

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.

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.

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.

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.

Biodiversity?

Managing a wildlife population

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.

Environmental crisis lecture 8

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (19)

Ähnlich wie Environmental crisis lecture 8

Ähnlich wie Environmental crisis lecture 8 (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Environmental crisis lecture 8