Transcript Document

Species Diversity and Preservation I
Potential Test Questions
1. Distinguish threatened, endangered, and extinct species.
Explain four characteristics common to many
endangered species.
2. Discuss the main human causes for endangered species.
3. Discuss ways to slow or stop the decline in species
diversity.
Factors Affecting Biological Resources
Natural Processes (e.g., fires)
Land Use (e.g., urban development)
Water Use (e.g., hydroelectric)
Climate Change (e.g., global warming)
(http://observer.guardian.co.uk/international/story/0,6903,1153513,00.html)
Nonindigenous Species
Environmental Contaminants (e.g., oil spills)
Harvest (e.g., overfishing)
Species Diversity - Terrestrial
Species
Diversity
Definitions
Extinction: the irreversible loss or ‘death’ of a species.
Endangered species (ESA): a
species in imminent danger
of extinction throughout all
or a significant portion of its
range. (What is a species?)
Threatened species: a species
that is likely to become
endangered in all or a
significant portion of its
range.
Species Diversity
Characteristics of Endangered
Species
• Extremely small range - lily on single
hilltop near SF.
• Large territories - California condor. (+
issue of Minimum Viable Populations)
• Living on islands - endemics (living
nowhere else); evolved in isolation from
predators, disease, and competition.
• Low biotic potential - blue whales.
• Specialized breeding areas - green sea
turtles.
• Specialized feeding habitats - pandas and
bamboo.
Extinction
Mass Extinctions
Historic Peri od
Ti me (MYA)
Ordovician
De von ian
Pe rmi an
Tri assic
C retaceous
444
370
250
210
65
Q uaternary
present
Effects
_
25% of all fami l ies e xti nct
19% of all fami l ies e xti nct
54% of fam i l ei s, 90% of species exti nct
23% of fam i l ei s, 50% of species exti nct
17% of fam i l ei s, 50% of species exti nct (i ncl uding
di nosaurs but n ot m am mals)
1/3 to 2/3 of al l spe cies e xti nct if present trends
continue
If extinction is a natural process, why should we be
concerned about extinction?
Human-based Extinction:
Human disturbance dominates many landscapes, making
the processes of many ecosystems human-dominated.
Species Diversity - Loss of Ecosystems
Effects of
Human
Population on
Diversity
Human-based Extinction:
:We affect species through:
1.
2.
3.
4.
5.
6.
7.
Habitat Destruction
Hunting and Fishing
Predator Control
Pollution
Genetic Assimilation
Diseases
Exotic Species
Introductions
Species Diversity - Health of
Ecosystems
Species Diversity - Loss of Ecosystems
Habitat Destruction: conversion of wilderness into
human-based habitat; mainly for farming, range use, and
forestry, but also for urban centers.
Iowa has lost much greater than 90% of its wetlands.
Fragmentation can cause forests (or
prairies) to slowly become small islands of
wooded area that can be too small to
maintain breeding populations.
Fragmentation eliminates the core
environment, expanding the amount of edge
available for weedy species to invade, and
eliminates the environment some species
need to survive.
Critical Size of an Ecosystem
Amazonia example:
Thomas Lovejoy
created patches of
various sizes (from 1 to
1000 ha and a 10,000 ha
'mainland'). A hectare
(ha) = 10,000 sq
kilometers or ~ 2.5
acres
Results from Lovejoy’s Amazonia Studies
A guild of insectivorous birds (that feed on insects
fleeing swarming army ants) disappeared in 1, 10
hectare, and some 100 ha fragments plots.
Pollinators, euglossine bees, would not cross 100 m
cleared strips, so population biology of at least 30 plant
families dramatically affected.
Results from Lovejoy’s Amazonia Studies
Rain forest fragments in central
Amazonia were experienced a
dramatic loss of above-ground tree
biomass that was not offset by
recruitment of new trees. These losses
were largest within 100 meters of
fragment edges, where tree mortality
was sharply increased by
microclimatic changes and elevated
wind turbulence. Permanent study
plots within 100 meters of edges lost
up to 36% of their biomass in the first
10 to 17 years after fragmentation.
Results from Lovejoy’s Amazonia Studies
Dung and carrion feeding beetles responded similarly
to other insects, so the decomposition process slowed.
Much of the primate diversity went almost
immediately extinct in the isolated fragments.
Only 7 of 20 mammal species present in reserve areas
persisted in the first isolated fragments, and many of
those that persisted were those capable of surviving in
disturbed areas or secondary vegetation.
Minimum Viable Populations
Populations that are large enough that inbreeding does not
cause the species to go extinct.
If Minimum Viable Populations are not maintained, the
species cannot survive. (Plus, chance events have a greater
likelihood of eliminating a species that is already reduced in
numbers.)
Greater Prairie Chicken
Planned reserves on an ecosystem basis. For example, in
Yellowstone National Park (for watershed and wildlife
resources), more land would have to be added.
Protected Forests
Preservation and Park Usage in the U.S.A.
Threats to Parks:
1. Islands of nature
surrounded by destructive
land use.
Habitat destruction does not
end just because land is placed
into a reserve/preserve/park.
2. Roads, trails (especially
ATVs and off-road vehicles).
3. Visitor impact: Yosemite
National Park - 25,000
visitors for a 3-day weekend
(cars, laundries, concessions,
guest rooms, etc).
Corridors
Strips of habitat running between patches of habitat.
Used to allow movement of
species from one area to
another to help maintain
genetic exchange and prevent
extinction.
However, corridors can also
be a risk because they may act
as a corridor for disease,
invasive species, or as traps
for the species you are trying
to protect.
Hunting and Fishing
Consider the large Pleistocene mammals - extinctions
probably caused by human hunting - mammoths, mastadons
wooly rhinos, and ground sloths.
Hunting and Fishing
In the recent past, whales have been hunted to the brink of
extinction. Bison were once in the 10’s of millions, but
were reduced to less than 1000 individuals.
Passenger pigeons - now
extinct; once over 3 billion.
Predator/Pest Control
Involves top
predators
(keystone
species).
Wolves,
mountain lions,
gators.
American alligator:
top predator - keeps gar populations in check.
creates habitat diversity - islands created by nest mounds
gator trails - prevent marsh establishment
gator holes - provide habitat for other species in drought
Pollution
Amphibians as early
warning indicators. In
North America, and worldwide, amphibian
populations have drastically
declined and deformities
have increased.
Pollution
Environmental estrogens: (DDT, PCBs, Dioxins)
disrupt hormones; impact fish, reptilian, and
amphibian reproduction.
Acid precipitation: alters pH of water, thereby affecting
species.
Ozone depletion (due to CFCs): cause increased UV
light penetration and so cause higher mutation rates,
thereby affecting populations.
Global warming: temperature alterations can cause
population declines.
Species Diversity - Loss of Ecosystems
Genetic Assimilation
Classic definition is that genes of species at low population
numbers are at risk of being swamped if they hybridize with
close relatives.
With the use of genetically modified (GM) species in
farming, for example, could include the assimilation of
native species into closely related GM species.
Genetic Assimilation
Red wolf: predator control
and destruction of mature
woodland caused a reduction
in range and population size.
By 1970s, the species had
dwindled to a single
population in eastern Texas,
and this population is
threatened by interbreeding
with the close relative, the
coyote (Canis latrans).
Disease
Dutch elm disease owes its name to
the fact that it was first identified in
the Netherlands in 1921.
Dutch elm disease was first found in the United States in
Ohio in 1930. It has now spread throughout North America
and has destroyed over half the elm trees in the northern
United States. Dutch elm disease is caused by the fungus
Ophiostoma ulmi which is transmitted by two species of
bark beetles or by root grafting.
Powdery Mildew on Dogwoods
(Dogwood Anthracnose)
Powdery mildew, which is caused by the fungus
Microsphaeria penicillata.
Probably introduced into the United
States near Connecticut and Washington
State simultaneously in the mid-1970s.
Although it entered the U.S.A. at two
separate points, genetic analysis has
shown that the causal organism is the
same. However, the origin of this
pathogen remains unknown, as it has yet
to be identified on any species of
dogwood occurring outside the U.S.
Disease
American chestnut trees were once 1/4th of all trees in the
Appalachian Mountains. Infection by a fungal blight
destroyed all chestnuts of reproductive size.
Introduced Species
The fungus that destroys
the American chestnut was
introduced with a
shipment of nursery stock
from China in 1904, so it
was in actuality an
introduced exotic species.
Introduced Species