Transcript File

Biodiversity
Preservation
• Chapters 11, 12
US species
• Human Impacts on biodiversity
• Disturbed or degraded 40-50% of earth’s land
surface
• Use, destroy, or waste 40% of all terrestrial net
primary productivity
• According to WWF, 34% of fish species, 25% of
amphibians, 24% of mammals, 20% of reptiles, 14%
of plants, and 12% of birds are under threat of
extinction
• 95-98% of all virgin forests in US have been
destroyed since 1620
• • Difficulties in determining impact on biodiversity
Species diversity
• Richness (Number present)
• Evenness (Abundance)
• Species
richness
may be equal,
but relative
abundance
may
be different.
Fig. 53.21
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 2.1 The difference between species richness and
diversity. The diagram shows two samples, both containing
the same number of species and individuals (16 individuals
from 4 species), but with a clearly different balance of
species composition.
Habitat 1 (low diversity)
Habitat 2 (high diversity)
• Ecologists recognise that the diversity of an ecological
system has 2 facets:
– species number (=richness)
– evenness of distribution
Both these systems have 30 individuals and
3 species. Which is more diverse?
Sp. A Sp. B Sp. C
10
10
10
And how about this?
Sp. A Sp. B Sp. C
1
1
28
A B C
10 2 3
D E F
1 1 1
Number of bird
Species
Many groups
show strong
latitudinal gradients
in diversity
Number of Native Seed Plants
Region
Greenland
Arctic Alaska
Sonoran Desert
British Isles
Indiana
Central Coast, CA
North & South
Carolina
Costa Rica
Area (sq miles)
#
1,000,000
200,000
24,100
120,000
36,000
24,500
80,000
400
700
1500
1600
1900
3000
3150
18,400
8000
• The bottleneck effect occurs when the numbers
of individuals in a larger population are
drastically reduced by a disaster.
– By chance, some alleles may be over-represented
and others underrepresented among the survivors.
– Some alleles may be eliminated altogether.
– Genetic drift will
continue to impact
the gene pool until
the population is
large enough to
minimize the impact
of sampling errors.
Fig. 23.5
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Bottlenecking is an important concept in
conservation biology of endangered species.
– Populations that have suffered bottleneck incidents
have lost at least some alleles from the gene pool.
– This reduces individual variation and adaptability.
– For example, the genetic variation
in the three small surviving wild
populations of cheetahs is very low
when compared to other mammals.
• Their genetic variation is
similar to highly inbred
lab mice!
Fig. 23.5x
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Characteristics that make a species
more vulnerable to biological
extinction:
• Low reproductive rate (Kstrategists)—blue whales, giant pandas
• Specialized niche—giant pandas,
Everglades kite
• Narrow distribution—many island
species
• Feeds at high trophic level—Bengal
tiger, bald eagle, grizzly bear
• Fixed migratory patterns—whooping
crane, sea turtles
• Rare—many island species, some orchids
• Commercially valuable—tiger,
elephants, rhinoceros
• Large territories—California condor,
Florida panther
• Background Extinction (Natural rate
of extinction)—small number of
species become extinct naturally at a
low rate
• Estimate that more than 99.9% of all
species that have ever existed are now
extinct
• Background rate is thought to be 3-14
species per year (based on fossil
record)
•
Mass extinction—rise in extinction rates
above the background level.
• Catastrophic, widespread event in which
large groups of existing species are wiped
out
• Earth has experienced five mass
extinctions (20-60 million years apart)
• Adaptive radiations follow mass
extinctions when the diversity of life
increases and spreads
• Some biologists believe we are
currently experienced the sixth
mass extinction.
• 3-200 species become extinct
every day—well above
background levels.
– Several researchers estimate that at the current
rate of destruction, over half of all plant and
animal species will be gone by the end of this
new century.
– Extinction of species may be local, but it may
also be global.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Value of Wild Species
Critical Thinking
• Instrumental
– Sources for agriculture, forestry, aquaculture
and animal husbandry
– Recreational, aesthetic and scientific value
– Sources of medicine
Recreational, Aesthetic, and
Scientific Value
Introduced Species
• Rabbits in Australia (next slide)
• Chestnut blight in United States
• Japanese beetles, fire ants, gypsy moths in
United States
• Water hyacinth, kudzu, spotted knapweed,
purple loosestrife in United States
Rabbits Overgrazing in Australia
Strategies for
Conservation
Efforts
• Maximum sustainable yield:
The highest possible rate of use
that a system can match with its
own rate of replacement or
maintenance.
Ocean Ecosystems
75% of the Earth’s
surface
An international
commons?
Global Fish Harvests
100 million metric tons of
food on a sustained basis
Fisheries Problems
Too many boats
High technology
Too few fish
• Commercial fishing practices:
–
–
–
–
Bottom trawling
Long line fishing
Drift nets
Sonar
Fisheries in Distress
The Magnuson Conservation Act
of 1976
• Gave federal government authority to
manage fisheries
• Claimed the area between 3 and 200 miles
off shore as the “Exclusive Economic
Zone”
The Magnuson Conservation Act
of 1976
• Designed to
eliminate foreign
fishing
• Designed to restore
and conserve fish
Impacts of Magnuson Act
• Swapped foreign with
American exploiters
• Huge conflict of
interest among
council members
• Endangerment of 236
fish species
Sustainable Fisheries Act
• The 1996 reauthorization of the Magnuson
Act.
• Mandates that fish stocks be rebuilt
• Management plans and yields be based on
scientific data
• Steps be taken to minimize by catch
• Public and private lands in
the US.
Federal Lands (40%) In The U.S.
Wilderness Act of 1964
• Provides for permanent protection of
undeveloped and unexploited areas so that
natural ecological processes can operate
freely.
• 4% of land area in U.S.
• Preservation not conservation
• No permanent structures, roads, motor
vehicles
National Forests
• Only 5% of the
original U.S. Forests
are left
• Most U.S. Forests
are second growth
• National Parks (National Park Service)
• National Wildlife Refuges (Fish and
Wildlife Service)
• Next level of protection
–Protect and provide public access
New Forestry = Ecosystem
Management
•
•
•
•
•
Cut trees less frequently
Leave wider buffer zones along waterways
Leave dead logs and debris
Protect broader landscapes
Build no new roads until damage to old
ones is addressed
Private Land Trusts Protect Natural
Areas From Development
• Accept land as outright gifts
• Purchase land
Examples of Private Land Trusts
• Land Trust Alliance 4.7 million acres
• Nature Conservancy 11 million acres in
US 60 million in other countries
• Over 1200 trusts in 2000