Sustaining Biodiversity: The
Species Approach
Chapter 8
Three big ideas
• We are greatly increasing the extinction of wild species
• We should avoid causing the extinction of wild species
because of their economic and ecological value, and
because they exist.
• We can save some species and protect biodiversity
using your vote and your dollar!
(laws/treaties, protecting wildlife sanctuaries, and use of
the precautionary principle).
Section 8-1
Some human activities are
causing extinction rates to rise
• Extinction is a natural process… on average species
persist for 1-2 million years.
• What do you suppose the rate is now?
• The annual extinction rate is projected to rise to about
1% per year, mostly because of …
• At a 1% extinction rate, 25% - 50% of the world’s current
species could vanish by the end of this century.
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
Species are a vital part of the
earth’s natural capital
• Major reasons why we should work to
prevent our activities from causing the
extinction of other species:
• They provide natural resources and
natural services that help to keep us alive
and support human economies.
– Examples?
• Also provide economic benefits
– Examples?
Species are a vital part of the
earth’s natural capital
Major reasons why we should work to prevent
our activities from causing the extinction of
other species:
• Preserving species also provides economic
benefits through wildlife/eco tourism.
Species are a vital part of the
earth’s natural capital
• They losses are replaced VERY slowly
– Est. 5–10 million years for evolution to rebuild
biodiversity likely destroyed during your lifetime.
• Ethics!
– Many people believe that each wild species has
a right to exist, regardless its usefulness to us.
Section 8-3
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.
– Overexploitation
– Climate change.
– Disease
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.
– “Loss” 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
Harmful invasive species
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
Zebra mussels attached to a water
current meter in Lake Michigan
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
Bioaccumulation and
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.
Male mountain gorilla
Poached white rhinoceros
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
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.
What are the two major threats to
sea turtles?
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.
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
– 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?