Chapter 18-Conservation of Biodiversity
CORE CASE STUDY: Modern Conservation Legacies
I.
We are in the midst of a sixth mass extinction
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II.
Biological extinction: a species has disappeared from the earth.
Background extinction is an historic, continuous, low level of extinction.
Extinction rate is the percentage or number of species that go extinct each year.
Mass extinction is the loss of many species in a short period of time.
Extinction is natural, but there is evidence to suggest that it has accelerated as humans have
populated the earth.
 Humans have disturbed 50-80% of the earth.
Human activities increase the pace of extinction.
1. Current rate is 100—1,000 times the background rate (0.01–.1% per year).
2. Predictions hold that this will rise to 10,000 times that background rate during
this century.
Under this scenario ¼-1/2 of all species will be extinct by the end of the century.
Extinction estimates are likely conservative.
Rates will likely increase with the growing human population.
Rates tend to be much higher in biodiversity hotspots.
Habitat fragmentation limits the potential for speciation to occur.
Species heading toward biological extinction are either endangered or threatened.
1. Endangered species are so few in number that the species could soon become
extinct.
2. Threatened/vulnerable: still abundant but likely to become endangered in the
near future.
Global Declines in the Genetic Diversity of Wild Organisms
Global Declines in the Genetic Diversity of Crops and Livestock
Global Declines in Species Diversity
Global Declines in Ecosystem Function
Declining biodiversity has many causes
a. Habitat Loss
 The loss, degradation, and fragmentation of habitat are the greatest threat to a
species.
 Deforestation in tropical forests is the greatest species eliminator followed by loss
of wetlands and plowing of grasslands.
 Island species are especially vulnerable to extinction. Many are endemic.
 Habitat islands are isolated and surrounded by other habitats.
 Habitat fragmentation occurs when large contiguous habitats are divided into
isolated patches.
b. Alien Species
 After habitat loss, introduced species are the biggest cause of extinction.
 The alien species can be introduced accidentally or deliberately.
 Some of these species threaten and endanger native species.
 They have no natural predators, competitors, or pathogens in their new habitat.
 They can trigger ecological disruptions.
 There are an estimated 7,100 invasive species that have caused ecological or economic
harm in the U.S.
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 Invasive species are often introduced accidentally.
 Argentine ants aggressively attack native ant populations.
 The best control is to prevent the nonnative species from being introduced.
c. Overharvesting
 Overpopulation and excessive consumption of resources eliminate habitat.
 The World Conservation Union has kept Red Lists that are the world standard
for listing all threatened species throughout the world.
 Poaching—illegal killing of protected species.
1. Some protected species are killed for their valuable parts or are sold live
to collectors.
2. Earns smugglers $600,000 per hour in total.
3. Low-risk, because smugglers are rarely caught and punished.
 Global legal and illegal trade in wild species for pets is a very profitable
business.
1. More than 60 bird species, mostly parrots, are endangered or
threatened because of the wild bird trade.
2. Amphibians, reptiles, mammals, and tropical fish are also being
depleted because of pet trade.
3. Exotic plants (such as orchids and cacti) are often sold to collectors for
high prices.
 Bushmeat supplies indigenous people with food and has been harvested
sustainably, but as demand has gone up illegal hunting has skyrocketed.
1. Responsible for many local extinctions in West and Central Africa.
2. These hunting practices have resulted in negative ecological impacts
and have driven at least one species to extinction.
3. Butchering and eating bushmeat has helped spread Ebola and AIDS
from animals to humans.
d. Pollution
 Pollution from chemicals like pesticides can have unintended effects on species.
e. Climate Change
 Human activities induce rapid climate changes, increasing extinction rates.
III.
The conservation of biodiversity often focuses on single species
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Biologists site four reasons we should prevent our activities from causing extinctions.
1. Species are a vital part of earth’s life support system.
2. Species support our economy (materials, medicines, ecotourism).
3. It will take millions of years for natural speciation to rebuild biodiversity.
4. Species have a right to exist, regardless of their usefulness.
a. Conservation Legislation
 Treaties help protect endangered and threatened species, but enforcement is
difficult and punishment inadequate.
 The 1975 Convention on International Trade in Endangered Species (CITES) protects
900 species from being commercially traded and restricts international trade for
29,000 species that may become threatened.
a. Enforcement is difficult and varies from country to country.
b. Many countries are not signatories and still trade in animals.
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c. The Convention on Biological Diversity binds governments to reverse the global
decline in biological biodiversity. The U.S. has not ratified this treaty. There are
no penalties or enforcement mechanisms in place.
 The Endangered Species Act of 1973 identifies and legally protects endangered species in
the U.S. and abroad.
a. Identification of endangered, threatened ocean species is made by the
National Marine Fisheries Service, and the U.S. Fish and Wildlife Service
is responsible for identifying and listing all other endangered and
threatened species.
 Biological facts form the basis of inclusion on the endangered list.
 Habitats of endangered species must be protected.
a. Efforts have been made to repeal/weaken the Endangered Species Act.
b. Conservation biologists believe that the ESA should be strengthened and
modified to correct deficiencies.
b. The Convention on Biological Diversity
IV.
The conservation of biodiversity sometimes focuses on protecting entire
ecosystems
A. The Size, Shape and Connectedness of Protected Ares
 The sanctuary approach is being used to protect wild species.
 548 federal refuges protect wildlife but the habitats are deteriorating due to
invasive species, pollutants, and little operational or maintenance funding.
 More than three-fourths of the refuges are concentrated along major bird
migration corridors.
 About one-fifth of U.S. endangered and threatened species have habitats in the
refuge system.
 Activities considered harmful to wildlife take place in nearly 60% of wildlife
refuges.
 Gene banks, botanical gardens, and farms can be used to raise threatened species
and help protect species from extinction; but funding is inadequate.
 The world’s 1600 Botanical Gardens and Arboreta contain almost one-third of
the world’s known plant species, but only 3% of the world’s rare and threatened
species.
 Raising some threatened or endangered species on farms can take some of the
pressure off them and perhaps offer some for commercial sale.
 Zoos and aquariums can help protect some endangered animal species as well.
 Egg pulling collects wild eggs laid by endangered bird species and hatches them in
zoos/research centers.
 Captive breeding takes wild individuals into captivity for breeding with the
commitment to reintroduce the offspring back into the wild.
 Artificial insemination, use of surrogate mothers, use of incubators, and crossfostering by a similar species are other ways to increase populations of rare
species.
 The ultimate goal is to reintroduce these species into the wild.
 Reintroductions of endangered species to the wild fail because:
 There is not suitable habitat.
 Individuals bred in captivity are not able to survive in the wild.
 There is renewed overhunting/capture of the returned species.
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