Transcript Benefits of biodiversity

Scott Brennan • Jay Withgott
10
Biodiversity and
conservation biology
PowerPoint® Lecture prepared by Jay Withgott
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
This lecture will help you understand:
• The scope of biodiversity on
Earth
• Extinction rates and mass
extinction events
• Causes of biodiversity loss
• Benefits of biodiversity
• Conservation biology
• Island biogeography theory
• Approaches to conservation
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Central Case: Saving the Siberian Tiger
• Several types of tigers used to roam throughout Asia.
• Some types are extinct; the Siberian tiger is endangered.
• Conservation biologists have worked hard to save the
tiger by educating people, preserving its habitat, and
breeding them in zoos. Their efforts are now paying off.
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“Biodiversity”
Biodiversity, or biological diversity = the sum of an area’s
organisms, considering the diversity of species, their genes,
their populations, and their communities
There is no one exact definition of biodiversity; people have
conceived of it in many ways.
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Biodiversity’s foremost spokesman
Biologist Edward O. Wilson has become the best-known
spokesperson for biodiversity.
An accomplished scientist and writer, he has raised
awareness of threats to Earth’s life, and of impending
species extinctions.
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Figure 15.1
Components of biodiversity
Biodiversity exists on several levels:
Genetic
diversity
Species
diversity
Ecosystem
diversity
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Figure 15.2
Species diversity
The number or variety of
species in a particular region
Species richness = number of species
Evenness, or relative abundance = extent to which numbers
of different species are equal or skewed
Species = a particular type of organism; a population or
group of populations whose members share certain
characteristics and can freely breed with one another and
produce fertile offspring
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Figure 15.2
Genetic diversity
Includes the differences
in DNA composition
among individuals
within a given species
Adaptation to particular environmental conditions may
weed out genetic variants that are not successful.
But populations benefit from some genetic diversity, so as
to avoid inbreeding or disease epidemics.
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Figure 15.2
Ecosystem diversity
Includes diversity
above the species
level
Biologists have viewed diversity above the species level in
various ways. Some alternative ways to categorize it
include:
Community diversity
Habitat diversity
Landscape diversity
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Figure 15.2
Species and taxonomy
Each species is
classified within a
hierarchy
reflecting the
evolutionary
diversification of
life.
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Two related
species might be
in the same genus;
two related genera
in the same
family, etc. Figure 15.3
Diversity of subspecies
Within species,
diversity exists in
subspecies, or
geographic
variations.
The tiger,
Panthera tigris,
had 8 subspecies.
5 persist today,
including
Panthera tigris
altaica, the
Siberian tiger.
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Figure 15.4
Measuring biodiversity
We are still profoundly ignorant of the number of species
that live on our planet.
Roughly 1.75 million species have been formally described
by science.
But many more exist:
Estimates range from 3 million to 100 million.
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Measuring biodiversity
Why are we still so unsure of the number of species on
Earth?
• Some areas remain little explored (hydrothermal
vents, rainforest canopies, tropical soils).
• Many species are tiny and inconspicuous (microbes,
roundworms, protists, fungi…).
• Some species are very similar in appearance (many
taxa, even trees, birds, whales).
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Distribution of biodiversity
Species are not evenly spread among different groups.
Insects comprise more than half of all species in
world.
Beetles comprise fully 40% of all insects.
Mammals are outnumbered by spiders and their
relatives 16 to 1.
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Distribution of biodiversity
Size of each
organism is
scaled to its
number of
species.
Mammals are
located in
front of the
insect’s
mandibles.
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Figure 15.5a
Distribution of biodiversity
Some groups that have more species may have gone
through an adaptive radiation.
This is when an ancestral species give rise to many species
that fill different niches, adapting to them by natural
selection.
Darwin’s Galápagos finches
Hawaiian honeycreepers
Asteraceae—daises and relatives
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Distribution of biodiversity
Another pattern in the
uneven distribution of
biodiversity is the
latitudinal gradient:
species richness
increases toward the
equator.
30–100 bird species in
large area of the Arctic
500–700 bird species in
small area of the tropics
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Figure 15.6
Latitudinal gradient
Ecologists are not certain why the latitudinal gradient exists,
but one prevalent idea is that tropical climates encourage
specialist species that can pack tightly in a community.
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Figure 15.7
Biodiversity loss and species extinction
Extinction = last member of a species dies and the species
vanishes forever from Earth
Extirpation = disappearance of a particular population, but
not the entire species globally
These are natural processes.
On average one species goes extinct naturally
every 500–1,000 years—this is the background
rate of extinction.
99% of all species that ever lived are now extinct.
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Mass extinctions
Earth has experienced five mass extinction events in which
over half its species were wiped out suddenly.
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Figure 15.8
Today’s mass extinction
Currently Earth is undergoing its sixth mass extinction—
because of us.
Humans have increased the extinction rate by a factor of
1,000.
1,100 species are known to have gone extinct in the past
400 years.
The Red List, from the IUCN, lists species that today are
facing high risks of extinction.
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Today’s mass extinction
Species of large
mammals and birds
plummeted with the
arrival of humans,
independently, on each
of three continents—
suggesting that human
hunting was the cause.
Figure 15.9
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Causes of species extinction
Primary causes spell “HIPPO”:
• Habitat alteration
• Invasive species
• Pollution
• Population growth
• Overexploitation
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“HIPPO”: Habitat alteration
The greatest cause of extinction today
Accounts for 85% of population declines of birds and
mammals
Habitat change hurts most organisms because they are
adapted to an existing habitat.
Alteration due to:
Forest clearing
Urban development
Agriculture
Global climate change
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etc….
“HIPPO”: Invasive species
Accidental or intentional introduction of exotic species to
new areas
Most do not establish or expand, but some do—likely
because they are “released” from limitations imposed by
their native predators, parasites, and competitors.
In today’s globalizing world,
invasive species have become perhaps the secondworst threat to native biota.
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“HIPPO”: Invasive species
Examples:
• Mosquito fish
• Zebra mussel
• Kudzu
• Asian longhorned beetle
• Rosy
wolfsnail
• Cane toad
• Bullfrog
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• Gypsy
moth
• European
starling
• Indian
mongoose
• Caulerpa
algae
• Cheatgrass
• Brown
tree snake
Figure 15.10
“HIPPO”: Pollution
Air and water pollution; agricultural runoff, industrial
chemicals, etc.
Pollution does serious and widespread harm, but is not as
threatening as the other elements of HIPPO.
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“HIPPO”: Population growth
Human population growth exacerbates every other
environmental problem.
Magnifies effects of the other elements of HIPPO:
More people means more habitat change, more
invasive species, more pollution, more
overexploitation.
Along with increased resource consumption, it is the
ultimate reason behind proximate threats to biodiversity.
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“HIPPO”: Overexploitation
Two meanings:
Overharvesting of species from the wild
(too much hunting, fishing…)
Overconsumption of resources
(too much timber cutting, fossil fuel use…)
Usually overexploitation is not the sole cause of extinction,
but it often contributes in tandem with other causes.
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Causes of species extinction
In most cases, extinctions occur because of a combination
of factors.
e.g., current global amphibian declines are thought
due to a complex combination of:
• Chemical contamination
• Disease transmission
• Habitat loss
• Ozone depletion and UV penetrance
• Climate change
• Synergistic interaction of these factors
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Benefits of biodiversity
Preserving biodiversity preserves ecosystem services, and
directly provides things of pragmatic value to us.
• Food, fuel, and fiber
• Shelter and building materials
• Air and water purification
• Waste decomposition
• Climate stabilization and moderation
• Nutrient cycling
• Soil fertility
• Pollination
• Pest control
• Genetic resources
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Benefits of biodiversity: Food security
Many species not
now commonly used
for food could be.
Genetic diversity
within crop species
and their relatives
enhances our
agriculture and
provides insurance
against losses of
prevalent strains of
staple crops.
Figure 15.11
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Benefits of biodiversity: Medicine
Many species can
provide novel medicines;
we don’t want to drive
these extinct without ever
discovering their uses.
Ten of our top 25 drugs
come directly from wild
plants; the rest we
developed because of
studying the chemistry of
wild species.
Figure 15.12
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Benefits of biodiversity: Economic benefits
For all nations, ecotourism can be a major
contributor to the economy—especially for
developing nations rich in biodiversity.
Affluent tourists pay good money to see wildlife,
novel natural communities, and protected
ecosystems.
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Benefits of biodiversity: “Biophilia”
Biophilia = human love for and attachment to other living
things;
“the connections that human beings subconsciously
seek out with the rest of life”
e.g., Affinity for parks and wildlife
Keeping of pets
Valuing real estate with landscape views
Interest in escaping cities to go hiking,
birding, fishing, hunting, backpacking…
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Conservation biology
Scientific discipline devoted to understanding the factors, forces, and processes
that influence the loss, protection, and restoration of biological diversity within
and among ecosystems.
Applied and goal-oriented: Conservation biologists intend to prevent extinction.
This discipline arose in recent decades as biologists grew alarmed at the
degradation of natural systems they had spent their lives studying.
Figure 15.13
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Equilibrium theory of island biogeography
Explains how species diversity patterns arise on islands, as a
result of:
•
Immigration
•
Extinction
•
Island size
•
Distance from the mainland
The theory originally developed as basic science for oceanic
islands.
Then it was found to apply to islands of habitat (fragments)
within terrestrial systems, for conservation biology.
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Species-area curves
The prediction of an
increase in species with
increased area of an
island is borne out by
data from nature.
Here, species richness on
islands of the Caribbean.
Figure 15.15
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Testing island biogeography theory
The theory was first tested experimentally on small
mangrove islands in the Florida Keys.
All arthropods were extinguished from them with a
pesticide, and then the researchers observed as species
returned to the islands. Equilibrium numbers matched their
predictions, supporting the theory.
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From The Science behind the Stories
Island biogeography theory in conservation
The theory’s
applicability to
conservation became
clear when a
researcher
documented historical
declines in mammals
in national parks. The
extinctions matched
predictions of the
theory if the parks
were thought of as
islands.
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From The Science behind the Stories
Fragmentation
“Islands” of interest to
conservation biologists include
forest fragments.
Forest fragmentation occurs
as continuous forest habitat
gets broken up gradually.
This leads to local extirpations
of forest species, as fragments
become too small to support
them, and too distant to allow
immigration.
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Conservation approaches: Umbrella species
When habitat is preserved to meet the needs of an “umbrella
species,” it helps preserve habitat for many other species.
(Thus, primary species serve as an “umbrella” for others.)
Large species with large home ranges (like tigers and
other top predators) are good umbrella species.
So are charismatic ones that win public affection, like
the panda.
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Conservation approaches: Endangered
species
Trying to preserve single species threatened with extinction
is the goal of endangered species laws, although they often
also achieve umbrella conservation.
U.S. Endangered Species Act, 1973:
• Restricts actions that would destroy endangered
species or their habitats
• Forbids trade in products from species
• Prevents extinction, stabilizes and recovers
populations
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Conservation approaches: Endangered
species
The ESA has had notable successes:
Bald eagle
Peregrine falcon
40% of all declining populations held stable
However, there is much popular resentment against the ESA:
Many citizens believe it will restrict their
freedom if endangered species are found on their land.
Canada therefore stressed cooperation with landowners and
provincial governments in its recent Species at Risk Act.
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Conservation approaches: Captive breeding
Many endangered species are being bred in zoos,
to boost populations
and reintroduce them into the wild.
This has worked so far for
the California condor
(in photo, condor hand puppet
feeds chick so it imprints on
birds, not humans).
But this is worthless if there
is not adequate habitat left in
the wild.
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Figure 15.17
Conservation approaches: Cloning
A newly suggested approach is to use molecular
techniques to clone endangered or even extinct species,
raise them in zoos, and reintroduce them to the wild.
Even if this succeeds technically, though, it will be
worthless if there is not adequate habitat and protection
left for them in the wild.
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Conservation approaches: International
treaties
Various treaties have helped conserve biota.
A major one is CITES, the Convention on International
Trade in Endangered Species of Wild Fauna and Flora,
prepared in 1973.
It bans international trade and transport of body parts of
endangered organisms.
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Conservation approaches: International
treaties
The Convention on Biological Diversity (CBD), from the
Rio Conference in 1992, aims to:
• Conserve biodiversity
• Use it sustainably
• Ensure fair distribution of its benefits
The CBD has been signed by 188 nations, but not by the
United States.
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Conservation approaches: Biodiversity
hotspots
Biodiversity hotspot = an area that supports an especially
high number of species endemic to the area, found nowhere
else in the world
Endangered golden lion
tamarin, endemic to Brazil’s
Atlantic rainforest, which
has been almost totally
destroyed
Figure 15.18
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Conservation approaches: Biodiversity
hotspots
Global map of biodiversity hotspots, as determined
by Conservation International
Figure 15.19
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Viewpoints: Biodiversity
Norman
Myers
“If we could safeguard
biodiversity hotspots, we could
reduce the number of extinct
species by at least one-third.
However, global warming will
shift temperature bands and
vegetation communities, so these
areas would still be vulnerable.”
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Peter
Kareiva
“Parks are a valuable strategy
for conservation, but they are
not the most important strategy.
Conservation cannot just be
about setting aside nature in
parks but rather must address
working landscapes and human
use of biological resources.”
From Viewpoints
Conclusions: Challenges
We still have little idea of how many species inhabit our
planet.
We have set the sixth mass extinction in motion.
Population declines, extirpations, and extinctions result
from habitat alteration, invasive species, pollution,
population growth, and overexploitation.
Fragmentation of habitats causes loss of species from
habitat islands.
Conservation biology is fighting an uphill battle to save
species, habitats, and ecosystems.
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Conclusions: Solutions
Biologists are making strides in determining how many
species inhabit our planet.
There is still time to halt the sixth mass extinction.
We have ways to minimize habitat alteration, invasive
species, pollution, and overexploitation, but success will
ultimately depend on halting human population growth.
Fragmented habitats can be restored, but preserving areas
before they are fragmented is best to avoid species loss.
Conservation biology has developed numerous and varied
ways to save species, habitats, and ecosystems.
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QUESTION: Review
Which of these pairs of terms is included in the acronym
“HIPPO” that describes causes of biodiversity loss?
a. Pollution and Indicator species
b. Harvesting and Population decline
c. Habitat alteration and Invasive species
d. Overexploitation and Pollination
e. Indicator species and Population growth
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QUESTION: Review
Which is NOT a benefit of biodiversity to humans?
a. Economic benefits through ecotourism
b. New potential sources of food
c. New potential sources of drugs
d. Ecosystem services
e. All of the above are benefits of biodiversity.
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QUESTION: Review
Which has NOT been an approach of conservation
biologists?
a. Identifying and mapping areas with large
numbers of endemic species.
b. Applying island biogeography theory to habitat
fragments.
c. Breeding animals in captivity.
d. Requiring landowners to give up their land.
e. Working with local communities to get them
invested in conservation.
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QUESTION: Weighing the Issues
When North American pharmaceutical companies go
“bioprospecting” in developing countries for compounds for
new drugs and medicines, should they be required to pay the
host country for its biodiversity?
a. Yes; the biodiversity is a natural resource of the
host country, and it should be paid a fee up front.
b. Yes; the biodiversity is a natural resource of the
host country, and it should share in any eventual
profits from any medicines developed.
c. No; the company is the one doing all the work, so
all profits should go to the company.
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QUESTION: Viewpoints
Are parks and protected areas the best strategy for
protecting biodiversity?
a. Yes; it is absolutely necessary to preserve
untrammeled habitat for species to persist.
b. No; parks won’t matter because climate change
will force the biota out of them.
c. No; it is more effective to work with local
people and give them economic incentives to
conserve nature.
Both parks and other strategies are necessary.
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