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BIOL 1602 Lecture Notes - Endangered Species, Conservation Biology, Species Richness

Course Code
BIOL 1602
Rebecca Jubis

of 6
Chapter 57 – Conservation Biology
Conservation biology – an applied scientific discipline devoted to preserving the
diversity of life on Earth
modern conservation biology is supported by and integrated with other
scientific disciplines
humans study the full array of goods and services that humans derive from
species and ecosystems
it's a normative discipline – embraces certain values and applies scientific
methods to the goal of achieving these values
motivated by belief that preservation of biodiversity is good and that its loss is
Conservation biology is guided by 3 basic principles:
Evolution is the process that unites all of biology
The ecological world is dynamic
Humans are a part of ecosystems
early photosynthetic prokaryotes and eukaryotes generated oxygen, making Earth's
atmosphere unsuitable for anaerobic organisms
plants accelerated weathering of the rocks, gaining access to rock-bound nutrients
endemic species – species that are found nowhere else
humans have been exterminating species for 1000s of years due to over-hunting
People value biodiversity because:
Humans depend on other species for food, fiber and medicine
Species are necessary for the functioning of ecosystems and the many
benefits and services those ecosystems provide to humanity
Human derive enormous aesthetic pleasure from interacting with other
Extinctions deprive us of opportunities to study and understand ecological
relationships among organisms
Living in ways that cause extinction of other species raises serious ethical
issues because species are judged to have intrinsic value
How Do Biologists Predict Changes in Biodiversity?
To preserve Earth's biodiversity, we need to both maintain the processes that
generate new species and provide conditions that will keep extinction rates no
higher than typical levels
4 reasons that scientists cannot predict the number of extinctions that will occur:
We do not know how many species live on Earth
We do not know where species live
It is difficult to determine when a species actually becomes extinct
We do not know what will happen in the future
North America's largest woodpecker, the ivory-billed pecker, was considered extinct
for 60 years until recently where there have been claimed sightings
Species-area relationship – a well-established mathematical relationship between the
size of an area and the number of species it contains
conservation biologists have measured the rate at which species richness decreases
with decreasing habitat patch size
found that a 90% loss of habitat will result in the loss of half the species that
live in and depend on that habitat
current loss of tropical evergreen forests (the most species-rich biome) is 2%
per year
conservation biologists develop statistical models that incorporate information about
a population's size, its genetic variation, morphology, physiology and behaviour of its
members to estimate risks of extinction
Endangered species – in imminent danger of extinction in all or a specific part
of their range
Threatened species – likely to become endangered in the future
rarity is not a cause for concern
species whose populations are suddenly shrinking rapidly are usually at high risk
species with special habitat or dietary requirements are more likely to become
populations with a few individuals confined to a small range can be easily eliminated
by local disturbances
the golden toad in Costa Rica became extinct due to climate warming
What Factors Threaten Species Survival?
habitat loss is most important cause of species endangerment in the U.S. Especially
for species in freshwater
Fragmentation – as habitats are progressively lost to human activities, the remaining
patches become smaller and more isolated
small patches cannot maintain populations of species that require large areas
Edge effects - the fraction of a patch that is influenced by factors originating outside
it increases rapidly as patch size decreases
species from surrounding habitats colonize on the edges of patches to
compete with or prey on species living there
species disappeared from isolated patches when the surrounding forest was
species that are lost from small habitat fragments are unlikely to become
reestablished there because dispersing individuals are unlikely to find isolated
a species may persist in a small patch if it is connected to other patches by
corridors of habitat through which individuals can disperse
Invasive – when species spread widely and become unduly abundant, often at a cost
to the native species of the region
most introduced species are imported without their natural enemies, while native
plants must devote considerable energy to defending themselves against the native
invasive plants generally have high rates of growth and reproduction because
they spend less energy in producing defensive compounds
introduced pathogens have destroyed whole populations of several eastern
North American forests
disease outbreaks usually leave no traces in the fossil record
due to human activities, average temperatures in North America will increase about
organisms that are able to disperse easily may be able to shirt their ranges as
rapidly as the climate changes provided that appropriate habitats exist in new areas
ranges of species with sedentary habits are likely to shift slowly
if Earth's surface warms as predicted, new climates will develop and existing
climates will disappear
new climates are certain to develop at low elevations in the tropics
if warming of oceans continues about 40% of coral reefs are likely to be killed
reefs adjacent to cool, upwelling waters and reefs in cloudy waters have
relatively low temperatures and are healthy
What Strategies Do Conservation Biologists Use?
Protected areas – an important component of efforts to preserve biological diversity
preserve habitats while preventing the human exploitation of the species
living there may serve as nurseries from which individuals disperse into
exploited areas
The fundamental requirement for the conservation of biological diversity is the
in situ conservation of ecosystems and natural habitats and the maintenance
and recovery of viable populations of species in their natural surroundings –
United Nations Convention
How to select areas being protected
Species richness – the number of species living in an area
then umber of endemic species
biodiversity “hotspots” occupy 15.7% of Earth's land surface but are home to 77% of
Earth's terrestrial vertebrate species
hotspots are also regions of high human populations whee habitat destruction
is a major problem
WWF identified 200 regions of great conservation importance, including marine
areas, tundra, boreal forests and deserts
conservation biologists have analyzed distributions of animals and have identified
595 centers of imminent extinction
the sites harbor 794 species judged to be at serious risk of extinction
Restoration ecology – methods that attempt to restore natural habitats
many degraded ecosystems will not recover without human assistance
many grassland habitats grow on rich soils but humans have converted them to
agricultural use
North American prairies have been converted to cropland or have been used
to domesticate livestock
a major prairie restoration is underway in northeastern Montana to restore 15
This project is feasible form any reasons:
the private land is owned by a small number on ranchers and each
ranch owns extensive grazing leases on nearby public lands
most of the land has never been plowed, so native vegetation is
most likely to recover when grazing pressure is reduced
the area is steadily losing its human population
the American Prairie Foundation is buying ranches and restoring wildlife
and black-footed ferrets, the most endangered mammal in North America
many species depend on particular patterns of disturbances on the landscape such
as fires and windstorms
conservation biologists work to assess whether reestablishment of historic
disturbance patterns can help preserve biodiversity
many plant species require periodic fires for successful establishment and survival
but however controlled burning is a common forest management tool
scars in the annual growth rings of trees preserve evidence of past fires that
didn't kill them
researchers can determine when fires occurred, how severe they were and