Transcript Chap 8 14e

Sustaining Biodiversity: The
Species Approach
Chapter 8
Three big ideas
• We are greatly increasing the extinction of wild species
by destroying and degrading their habitats, introducing
harmful invasive species, and increasing human
population growth, pollution, climate change, and
overexploitation.
• We should avoid causing the extinction of wild species
because of the economic and ecological services they
provide, and because their existence should not depend
primarily on their usefulness to us.
• We can work to prevent the extinction of species and to
protect overall biodiversity by using laws and treaties,
protecting wildlife sanctuaries, and making greater use of
the precautionary principle.
Section 8-1
WHAT ROLE DO HUMANS
PLAY IN THE EXTINCTION OF
SPECIES?
Extinctions are natural but
sometimes they increase sharply
• Biological extinction occurs when a
species can no longer be found anywhere
on the earth.
• The disappearance of species can weaken
or break some of the connections in the
ecosystem.
• The extinction of many species in a
relatively short period of geologic time is
called a mass extinction.
Some human activities are
causing extinction rates to rise
• Extinction is a natural process but evidence indicates
that extinction has accelerated as the human population
has increased, consuming huge quantities of resources
and creating large and growing ecological footprints.
• Scientists from around the world have estimated that the
current annual rate of species extinction is at least 100 to
1,000 times the background rate.
• The annual extinction rate is projected to rise to about
1% per year, mostly because of habitat loss and
degradation, climate change, and other environmentally
harmful effects of human activities.
• At a 1% extinction rate, 25% - 50% of the world’s current
species could vanish by the end of this century.
Some human activities are
causing extinction rates to rise
• A projected extinction rate of 1% a year may be
on the low side, for several reasons.
– The rate of species loss and the extent of biodiversity
losses are likely to increase sharply during the next 50–
100 years due to projected growth of the human
population.
– Current and projected extinction rates are much higher
than the global average in parts of the world that are
already highly endangered centers of biodiversity.
– Humans are creating a speciation crisis by eliminating
or degrading many biologically diverse environments
that are potential sites for the emergence of new
species.
Some human activities are
causing extinction rates to rise
• Human activities might help to increase the
speciation rates for other rapidly reproducing
opportunist species such as weeds, rodents,
insects, which could further accelerate the
extinction of other species.
Endangered and threatened species
are ecological smoke alarms
• An endangered species has so few individual
survivors that the species could soon become
extinct over all or most of its natural range.
• A threatened species (vulnerable species) still
has enough remaining individuals to survive in
the short term, but because of declining
numbers, it is likely to become endangered in
the near future.
• Some species have characteristics that make
them especially vulnerable to ecological and
biological extinction.
Characteristics that can put certain
species in greater danger of extinction
Percentages of various species threatened
with extinction due to human activities
Section 8-2
WHY SHOULD WE CARE
ABOUT THE RISING RATE OF
SPECIES EXTINCTION?
Species are a vital part of the
earth’s natural capital
• Three major reasons why we should work
to prevent our activities from causing the
extinction of other species:
– The world’s species provide natural resources
and natural services that help to keep us alive
and support human economies.
– Various plant species provide food crops,
fuelwood and lumber, paper, and medicine.
• Preserving species also provides economic
benefits through wildlife/eco tourism.
Species are a vital part of the
earth’s natural capital
• Analysis of past mass extinctions indicates
that it will take 5–10 million years for natural
speciation to rebuild the biodiversity that we
are likely to destroy during your lifetime.
• Many people believe that each wild species
has a right to exist, regardless its
usefulness to us.
Section 8-3
HOW DO HUMANS ACCELERATE
SPECIES EXTINCTION?
Loss of habitat is the single greatest
threat to species: Remember HIPPCO
• HIPPCO summarizes the most important
causes of extinction from human activities:
– Habitat destruction/degradation/fragmentation.
– Invasive (nonnative) species.
– Population growth/increasing use of resources.
– Pollution.
– Climate change.
– Overexploitation.
Loss of habitat is the single greatest
threat to species: Remember HIPPCO
• Scientists say that the greatest threat to wild
species is habitat loss, degradation, and
fragmentation. The greatest eliminators of
species are, in order:
– Deforestation in tropical areas.
– Destruction and degradation of coral reefs and
wetlands.
– Replacement of biologically diverse grasslands
with monoculture crops.
– Pollution of streams, lakes, and oceans.
Reductions in the ranges of four
species
Loss of habitat is the single greatest
threat to species: Remember HIPPCO
• Island species, often endemic species found
nowhere else on earth, are especially vulnerable
to extinction.
• Habitat fragmentation—by roads, logging,
agriculture, and urban development—occurs
when a large, intact area of habitat is reduced in
area and divided into smaller, more scattered and
isolated patches, or “habitat islands.”
• Most national parks and other nature preserves
are habitat islands.
We have introduced species
that can disrupt ecosystems
• After habitat loss and degradation, the biggest
cause of animal and plant extinctions is the
deliberate or accidental introduction of harmful
invasive species into ecosystems.
• Most species introductions are beneficial to us,
such as food crops, livestock and harvestable
trees.
• Problems arise when introduced species have
no natural predators, competitors, parasites, or
pathogens to help control their numbers in their
new habitat.
Harmful Invasive (Nonnative) Species
Deliberately Introduced Species
Purple
loosestrife
European
starling
African honeybee Nutria
(“Killer bee”)
Salt cedar
(Tamarisk)
Purple loosestrife African honeybeeWater hyacinth Japanese beetle European wild
(“Killer Bee”)
boar (Feral pig)
Fig. 8-7a, p. 159
Harmful Invasive (Nonnative) Species
Accidentally Introduced Species
Sea lamprey
(attached to
lake trout)
Argentina fire ant Brown tree
snake
Formosan termite Zebra mussel
Fig. 8-7b, p. 159
We have introduced species
that can disrupt ecosystems
• An estimated 7,100 species introduced
into the US have caused ecological and
economic harm.
• CASE STUDY: The Kudzu Vine.
– A deliberately introduced plant species; grows
rampant in the southeastern US and is known
as ‘the vine that ate the South’.
– In the 1930s, this vine was imported from
Japan and planted in the southeastern US in
an attempt to control soil erosion.
House overtaken by kudzu
Some accidentally introduced
species can disrupt ecosystems
• Many unwanted nonnative invaders arrive from
other continents as stowaways on aircrafts, ships,
wooden packing crates, on cars, or with tourists.
• Terrestrial examples include:
– The aggressive Argentina fire ant which has spread
over much of the southern US. Fire ants can wipe out
native ant populations. Fire ant mounds can cover
fields and yards. When disturbed, up to 100,000 ants
may attack with painful, burning stings. They have killed
deer fawns, birds, livestock, pets, and at least 80
people who were allergic to their venom.
Some accidentally introduced
species can disrupt ecosystems
– Pythons and boa constrictors have ended up in
the Everglades in Florida after being dumped
by their owners. Some reach 20 feet long and
200 pounds. They are hard to find and kill, and
they reproduce rapidly. They devour birds,
raccoons, pet cats and dogs, full-grown deer
and alligators. Tens of thousands of these
snakes now live in the Everglades and they
may spread to other swampy wetlands in the
southern half of the US.
Some accidentally introduced
species can disrupt ecosystems
• Bioinvaders also affect aquatic systems and are
blamed for about two-thirds of fish extinctions in
the US between 1900 and 2009
– The Great Lakes of North America have been invaded
by more than 185 alien species. At least 13 of the
recent invading species threaten some native species
and cause billions of dollars in damages.
– Fish-killing sea lamprey.
– Zebra mussel - displaced some species, depleted the
food supply for others and clogged pipes, shutting
down water intake pipes for power plants and city water
supplies, jammed ship rudders, and grown in huge
masses on boat hulls, piers and other solid surfaces.
Zebra mussels attached to a water
current meter in Lake Michigan
Prevention is the best way to reduce
threats from invasive species
• Scientists suggest several ways to do this:
– Fund a massive research program to identify
the major characteristics that allow species to
become successful invaders and the types of
ecosystems that are vulnerable to invaders.
– Greatly increase ground surveys and satellite
observations to detect and monitor species
invasions and to develop better models for
predicting how they will spread and what
harmful effects they might have.
Prevention is the best way to reduce
threats from invasive species
– Identify major harmful invader species and establish
international treaties banning their transfer from one
country to another, as is now done for endangered
species, while stepping up inspection of imported
goods to enforce such bans.
– Require cargo ships to discharge their ballast water
and replace it with saltwater at sea before entering
ports, or require them to sterilize such water or to
pump nitrogen into the water to displace dissolved
oxygen and kill most invader organisms.
– Educate the public about the environmentally harmful
effects of releasing exotic plants and pets into the
environment near where they live.
Ways we can slow or prevent
the spread of invasive species
Population growth, overconsumption, pollution,
and climate change can cause species extinctions
• Past and projected human population growth
and excessive and wasteful consumption of
resources have greatly expanded the human
ecological footprint, impacting other species.
• Pollution also threatens some species with
extinction, as has been shown by the
unintended effects of certain pesticides.
– Each year pesticides kill about 20% of the honeybee
colonies that pollinate almost 33% of U.S. food crops,
kill more than 67 million birds and 6–14 million fish
each year, and threaten about 20% of the country’s
endangered and threatened species.
Population growth, overconsumption, pollution,
and climate change can cause species extinctions
– The pesticide DDT can be biomagnified about
10 million times in an estuary food chain,
causing animals such as the osprey, brown
pelican and bald eagles to die.
• Projected climate change could help drive
a quarter to half of all land animals and
plants to extinction by the end of this
century.
Bioaccumulation and
biomagnification
CASE STUDY: Where Have All
The Honeybees Gone?
• About one-third of the U.S. food supply comes from
insect-pollinated plants, and honeybees are
responsible for 80% of that pollination.
• A 30% - 40% drop in U.S. honeybee populations
has been reported since the 1980s, due to:
–
–
–
–
–
Pesticide exposure.
Parasitic mites - can wipe out a colony in hours.
Invasion by Africanized honeybees.
A virus traced to Israel, and a certain fungus.
Poor nutrition because of a decrease in the natural
diversity of flowers and other plants on which bees feed.
CASE STUDY: Where Have All
The Honeybees Gone?
• In 2010, about 34% of commercial honeybee colonies in the
U.S. were lost in part to colony collapse disorder (CCD),
causing adult bees to mysteriously disappear.
• Strategies to help honeybee populations:
– Beekeepers are reducing CCD by practicing stringent hygiene,
improving the diets of the bees, and trying to reduce viral infections.
– Cut back on use of pesticides, especially at midday when honeybees
are most likely to be searching for nectar.
– Make our yards and gardens into buffets for honey bees by planting
native plants that they like.
– Bees need places to live, so some homeowners are purchasing bee
houses from their local garden centers.
Illegally killing, capturing, and selling
wild species threatens biodiversity
• Some protected species are poached for their
valuable parts or are sold live to collectors.
• The global illegal trade in wildlife brings in an
average of at least $600,000 an hour and at
least 66% of all live animals smuggled around
the world die in transit. Organized crime has
moved into illegal wildlife smuggling because of
the huge profits involved.
• Examples include:
– A highly endangered, live mountain gorilla is worth
$150,000.
Male mountain gorilla
Illegally killing, capturing, and selling
wild species threatens biodiversity
– The pelt of a critically endangered giant panda can
bring $100,000.
– A poached rhinoceros horn can be worth $25,000 per
pound. Rhinoceros are killed only for their horns.
– About 25,000 African elephants are killed illegally
each year for their ivory tusks despite an international
ban on the sale of poached ivory since 1989.
– A coat made from the fur of the Indian or Bengal tiger
can sell for as much as $100,000 in Tokyo, and the
body parts of a single tiger are worth as much as
$70,000. Without emergency action to curtail
poaching and preserve their habitat, few if any tigers
may be left in the wild within 20 years.
Poached white rhinoceros
Illegally killing, capturing, and selling
wild species threatens biodiversity
– More than 60 bird species, mostly parrots, are
endangered or threatened because of the wild-bird
trade.
– The pet trade is depleting populations of many
amphibians, various reptiles, some mammals, and
many tropical fishes. For each fish caught alive, many
more die, and the cyanide used to stun tropical fish
also kills the coral polyps that build reefs.
– Some exotic plants are endangered when they are
gathered to for houseplants and landscapes.
Collectors may pay $5,000 for a rare orchid or
$15,000 for a saguaro cactus.
Rising demand for bush meat
threatens some African species
• Indigenous people in much of West and Central Africa
have sustainably hunted wildlife for bush meat, a source
of food, for centuries.
• In the last two decades, bush meat hunting in some
areas has skyrocketed as hunters try to provide food for
rapidly growing populations or to make a living by
supplying restaurants with exotic meats.
• Bush meat hunting has led to the local extinction of
many wild animals, driven one species of colobus
monkey to complete extinction, and been a factor in
reducing some populations of orangutans, chimpanzees,
elephants, and hippopotamuses.
CASE STUDY: A Disturbing
Message from the Birds
• Approximately 70% of the world’s known
bird species are declining in number.
• The primary culprits appear to be habitat
loss and fragmentation.
Section 8-4
HOW CAN WE PROTECT WILD
SPECIES FROM EXTINCTION?
International treaties and national
laws can help to protect species
• The 1975 Convention on International Trade in
Endangered Species (CITES) is a far-reaching
treaty signed by 174 countries that bans the
hunting, capturing, and selling of threatened or
endangered species.
• The Convention on Biological Diversity (CBD),
ratified by 190 countries (but as of 2011, not by
the United States), legally commits participating
governments to reversing the global decline of
biodiversity and to equitably sharing the benefits
from use of the world’s genetic resources.
The U.S. Endangered Species Act
• The Endangered Species Act of 1973 (ESA; amended in
1982, 1985, and 1988) was designed to identify and
protect endangered species in the United States and
abroad.
• Under the ESA, the National Marine Fisheries Service
(NMFS) is responsible for identifying and listing
endangered and threatened ocean species, while the
U.S. Fish and Wildlife Service (USFWS) is to identify and
list all other endangered and threatened species.
• Any decision to add or remove a species on the list must
be based on biological factors alone without
consideration of economic or political factors.
The U.S. Endangered Species Act
• The ESA forbids federal agencies (except the
Defense Department) to carry out, fund, or
authorize projects that would jeopardize an
endangered or threatened species, or destroy or
modify its critical habitat.
• For offenses committed on private lands, fines
as high as $100,000 and 1 year in prison.
• Between 1973 and 2011, the number of U.S.
species on the official endangered and
threatened species lists increased from 92 to
more than 1,320.
The U.S. Endangered Species Act
• Since 1982, the ESA has been amended to give
private landowners economic incentives to help
save endangered species living on their lands.
• Some believe that the ESA should be weakened
or repealed, and others believe it should be
strengthened and modified to focus on
protecting ecosystems.
• The ESA and international agreements have
been used to identify and protect endangered
and threatened marine species such as seals,
sea lions, sea turtles, and whales.
CASE STUDY: Protecting
Endangered Sea Turtles
• Six of the world’s seven sea turtle species
are critically endangered or endangered.
• Two major threats to sea turtles are loss or
degradation of beach habitat (where they
come ashore to lay their eggs and the
young hatch), and the legal and illegal
taking of their eggs.
Endangered leatherback sea
turtle tangled in a fishing net
CASE STUDY: Protecting Whales:
A Success Story . . . So Far
• Easier to kill due to their large size and their
need to come to the surface to breathe.
– Whalers killed an estimated 1.5 million whales between
1925 and 1975, driving 8 of the 11 major species to
commercial extinction and driving the blue whale, the
world’s largest animal, to the brink of biological extinction.
– The International Whaling Commission estimates some
whale species are recovering, but many conservationists
fear that opening the door to any commercial whaling may
weaken international disapproval and legal sanctions.
– Despite the ban on whaling, more than 28,000 whales
were hunted and killed between 1986 and 2010, mostly by
the nations of Japan, Norway, and Iceland, which have
openly defied the ban.
We can establish wildlife refuges
and other protected areas
• In 1903, President Theodore Roosevelt
established the first U.S. federal wildlife
refuge at Pelican Island, Florida, to help
protect birds such as the brown pelican
from extinction.
• The National Wildlife Refuge System grew
to 553 refuges by 2011.
• More than three-fourths of the refuges
serve as wetland sanctuaries that are vital
for protecting migratory waterfowl.
We can establish wildlife refuges
and other protected areas
• One-fifth of U.S. endangered and threatened
species have habitats in the refuge system, and
some refuges have been set aside for specific
endangered species, such as Florida’s Key deer,
the brown pelican, and the trumpeter swan.
• Harmful activities to wildlife such as mining, oil
drilling, and use of off-road vehicles occur in
nearly 60% of the nation’s wildlife refuges.
• Wildlife refuges receive little funding; a third of
them have no staff, and structures in some
refuges are in disrepair.
Gene banks, botanical gardens, and
wildlife farms can help to protect species
• Gene or seed banks preserve genetic information
and endangered plant species by storing their
seeds in refrigerated, low-humidity environments.
• More than 100 seed banks worldwide collectively
hold about 3 million samples, however:
– Some species cannot be preserved in gene banks.
– The banks are expensive to operate and can be
destroyed by fires and other mishaps.
– A new underground vault on a remote island in the
Arctic will eventually contain 100 million of the world’s
seeds and will not be vulnerable to power losses, fires,
storms, or war.
Gene banks, botanical gardens, and
wildlife farms can help to protect species
• The world’s 1,600 botanical gardens and
arboreta contain living plants, representing
almost one-third of the world’s known plant
species but only about 3% of the world’s
rare and threatened plant species.
• Some endangered or threatened species
are raised on farms for commercial sale,
such as alligator farms in Florida and
butterfly Papua New Guinea.
Zoos and aquariums can protect
some species
• Zoos, aquariums, game parks, and animal
research centers are being used to
preserve some individuals of critically
endangered animal species, with the longterm goal of reintroducing the species into
protected wild habitats.
• Two preserving techniques are:
1. Egg pulling, where wild eggs laid by critically
endangered bird species are collected and
then hatched in zoos or research centers.
Zoos and aquariums can protect
some species
2. Captive breeding, where some or all of the
wild individuals of a critically endangered
species are captured for breeding in captivity,
with the aim of reintroducing the offspring into
the wild.
• Limited space and budgets restrict efforts
to maintain breeding populations of
endangered animal species that are large
enough to avoid extinction through
accident, disease, or loss of genetic
diversity due to inbreeding.
The precautionary principle
• Biodiversity scientists call for us to take
precautionary action to help prevent
premature extinctions and loss of
biodiversity.
– The principle advocates that when substantial
preliminary evidence indicates that an activity
can harm human health or the environment,
we should take precautionary measures to
prevent or reduce such harm even if some of
the cause-and-effect relationships have not
been established scientifically.
The precautionary principle
• Using limited financial and human resources
to protect biodiversity based on the
precautionary principle involves dealing with
three important questions:
– How do we allocate limited resources between
protecting species and protecting their habitats?
– How do we decide which species should get the
most attention in our efforts to protect species?
– How do we determine which areas of land and
water are the most critical to protect?