Transcript Habitat Destruction

Habitat Destruction
CHAPTER 23
23.1 The Loss of Biodiversity

Extinction – the disappearance of a species
from all or part of the species’ geographical
range

Biodiversity – the variety of species in an
ecosystem
The Loss of Biodiversity

Every species has a specific habitat that supplies
it’s needs

Destruction of this habitat decreases the
geographical range of a species
Extinction

Extinction are a natural part of ecosystem
function

More than 99% of species that have lived on
earth are extinct today

Species that lack adaptations for survival in a
changing ecosystem become extinct
Extinction

Rate of extinction and species appearance are
not steady

See Figure 23.1

Today may be another period of mass extinction
because of dominant species: humans
Loss of Habitat

Extinctions and loss of biodiversity often occur as
a result of human activity

Habitat destruction – disturbing the part of an
ecosystem that an organism needs to survive

Forms:
 Land
development (draining swamps/wetlands to
create, housing complexes, marinas, farmland, etc.)
 Altering
 Mining
the course of rivers: dams
and quarrying
Loss of Habitat

Native species are threatened by non-native
species

Alien species (invasive species) – non-native
species introduced to an area by humans

Examples: water hyacinth – introduced in
Louisiana from S. America has invaded 800,000
hectares of rivers and lakes across US to
California; outcompeted native plants
Loss of Habitat

Human activity is destroying or altering habitats
in all biomes

Urban sprawl – humans looking for a place to
live

https://www.youtube.com/watch?v=rPeg1tbBt0A
23.2 Humans and Habitats

150 years ago rainforests covered an area of
earth’s surface larger than the US

Percentage of destruction is equal to an area
the size of the state of Oregon (deforestation)
Causes of Deforestation

All rain forests are in developing countries

These countries are usually poor and have
rapidly growing populations

Figure 23.3
Population Growth

Populations in developing countries need food
and living space

Soil in rainforests is nutrient-poor so removal of
plants leads to mass erosion

Most of this land becomes barren and
unproductive in a few years
Demand for Resources

Developing nations have resources that
developed nations want

Rainforests in the Philippines, Thailand, Borneo,
and Indonesia are a large source of timber for
developed countries such as Japan and other
nations
Demand for Resources

In Central and S. America grass-fed beef is in
high demand so rainforests are cleared for
grazing lands
Demand for Resources

Rain forest regeneration times are unknown

It is estimated to be from hundreds to thousands
of years

If it is all destroyed, no organisms will be left to fill
in niches

If all rain forests are destroyed 70% of biodiversity
is lost from earth
Aquatic Habitat Destruction

All biomes are losing biodiversity

Wetlands and coral reefs are very productive
ecosystems

Both are affected by pollution and
development
The Everglades

The everglades are a large group of marshes in
southern Florida

Habitat for many organisms: grasses, fish,
invertebrates, and migrating birds

Everglades are prime real-estate property which
has been developed for housing and recreation
The Everglades

More than half of all wetlands in the US have
been destroyed

An estimated 175,000 hectares are destroyed
annually

US Congress and the State of Florida are working
to restore at least part of the everglades to their
natural state
The Aral Sea

The Aral Sea is a large, salt-water lake in a southern
desert of the former Soviet Union

See Figure 23.5

Used to be fourth largest lake in the world

Rivers were diverted for irrigation

Used to be 1000km3 ; now only about a third its size

Loss of 68,000km2 is very serious

Loss of aquatic ecosystems that fed fishing industry
23.3 The Importance of Biodiversity

Why is habitat destruction undesirable if it is a
natural part of all ecosystems?

Two part answer:
 1.
 2.
humans benefit directly from high biodiversity
the loss of biodiversity threatens the health of the
global ecosystem, and indirectly threatens human
health
Crop Genetics

Direct benefits of biodiversity include new
genetic material for farm plants

About 30 species of plants are grown as crops

Selective crossing produces plants with higher
yields
Crop Genetics

Genetic material from wild plants strains is used
to improve food crops

1978 – a variety of wild corn was found in Mexico

Crossbreeding with this wild type meant farmers
didn’t have to plow and sow from season to
season
Crop Genetics

Genetic material makes the global food supply
more flexible

Pathogens and insects evolve leaving crops
vulnerable

New varieties are need to survive evolving
pathogens

Habitat destruction threatens the survival of wild
type crops
Medicines

Natural chemicals are used in medicines

About 40% of all medicines used in the US come from
plants

Quinine – used to fight malaria – comes from Cinchona
plant

Digitalis – used to treat heart disease – comes from
foxglove

Some cancer treatments are being researched using
leaves from periwinkle plants and bark of the pacific
yew
Medicines

Unknown other medicines are undiscovered in
the rainforests

Habitat destruction may mean that many
medicines may never be discovered
Wilderness Areas

Other effects of declining biodiversity include
loss of recreational areas

Wilderness – an area where the ecosystem is
relatively undisturbed by the activities of humans
Ecosystem Destruction

Most dangerous characteristic of current mass
extinction is the pattern

Past extinctions follow a pattern

Extinction of dinosaurs left many species to fill in
gaps

Extinction today is the removal of many species
23.4 Controlling Habitat Destruction

Many rainforests lie in developing countries

Developed countries drive the cause of their
destruction in many cases

Developed countries can help slow its
destruction by decreasing demand
International Efforts

Progress has been made

Gene bank – a secure place where seeds,
plants, and genetic materials are stored

Gene banks are working to preserve as much of
earth’s biodiversity as possible (just in case)

Ending habitat destruction is the best idea
though
The Endangered Species Act

1973 – US Congress passed The Endangered
Species Act

Law requires the government to create a list of
endangered species in the US that are
endangered of becoming extinct

Government must help protect these species
Provisions of the Endangered
Species Act

US Fish and Wildlife Service keep a list of endangered or threatened
species

Threatened or endangered species may not be killed or caught

Threatened or endangered plants may not be disturbed

Threatened or endangered species and products may not be
bought or sold

Federal government may not construct any project that jeopardizes
endangered species

The US Fish and Wildlife Service must prepare a species recovery
plan for each threatened or endangered species