Chapter 57: Conservation Biology
57.1 What is Conservation Biology?
Devoted to preserving the diversity of life on Earth
Draws heavily on concepts and knowledge from population genetics, evolution, ecology,
biogeography, wildlife management, economics and sociology
Conservation biology is a normative scientific discipline
Conservation biology is a normative discipline embraces certain values and applies scientific
methods to the goal of achieving these values; motivated by the belief that preservation of
biodiversity is good and that loss is bad.
Is guided by three principles:
o Evolution is a process that unites all of biology.
o The ecological world is dynamic.
o Humans are a part of ecosystems.
Conservation biology aims to prevent species extinctions
Organisms have always altered Earth’s ecosystems.
Very first organisms probably reduced the supply of energetically and structurally useful
compounds (replacing them with waste products).
Early photosynthetic prokaryotes and eukaryotes generated oxygen (unsuitable for anaerobic
Plants colonized the land, accelerating the weathering of rocks thus, gaining access to rock-
Weathering of phosphorus increased global productivity = rise of oxygen concentrations.
Rise of vascular plants increased oxygen concentration; lower carbon dioxide concentrations.
Human beings cause extinctions of other species
o When first arrived in N. America (20 000 years ago), encountered a rich fauna of large
o Most species were exterminated (overhunting) within a few thousand years.
The productivity and richness of Earth’s biota has increased during the long course of life’s
evolution, but current situation is unique: all environmental changes are being caused by a
That’s why now more and more people value biodiversity for many reasons:
o Humans depend on other species for food, fiber, and medicine
o Species are necessary for the functioning of ecosystems and its many benefits and
o Humans derive enormous aesthetic pleasure from interacting with other organisms.
o Extinctions deprive us of opportunities to study and understand ecological relationships
o Living in ways that cause the extinction of other species raises serious ethical issues
57.2 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 at a typical level
There are four reasons why scientists cannot accurately predict the number of future
o Do not know how many species live on Earth.
o Do not know where species live (i.e. animal ranges are poorly known). o Difficult to determine when a species actually becomes extinct.
o Do not know what will happen in the future.
Regardless, there are some methods for estimating probable rates of extinction resulting from
human actions (e.g. habitat destruction).
Species area relationship—mathematical relationship between the size of an area and the
number of species that area contains.
Findings suggest that a 90 percent loss of habitat will result in the loss of half of the species that
live in and depend on that habitat.
Current rate of loss of tropical evergreen forests is about 2% of remaining forest each year; if
this continues, at least 1 million species there could become extinct during this century.
To estimate the risk that a population will become extinct, conservation biologists develop
statistical models that incorporate information about pop. size, its genetic variation, and the
morphology, physiology and behaviour of its members.
Species in imminent danger of extinction in all or a significant part of their range are labelled
Threatened species are likely to become endangered in the near future.
Rarity is not ALWAYS a cause for concern b/c some species that live in highly specialized habitats
(e.g. panda) have probably always been rare and are well adapted to those conditions.
Species whose populations suddenly shrink at rapid rates (i.e. “newly rare”) are usually at high
Species with special habitats or dietary requirements are more likely to become extinct that
species with more generalized requirements.
Populations with only a few individuals confined to a small range can easily be eliminated by
57.3 What Factors Threaten Species Survival?
Species are endangered by habitat loss, degradation, and fragmentation
Habitat loss is the most important cause of species endangerment.
A habitat loss also affects the remaining habitats that are not destroyed.
As habitats are progressively lost, the remaining habitat patches become smaller and more
isolated and becomes increasingly fragmented.
Small habitat patches are qualitatively different from larger patches of the same habitat in ways
that affect the survival of species.
Small patches cannot maintain populations of species that require large areas; can support only
small populations of many of the species that can survive in small patches.
The fraction of a patch that is influenced by factors originating outside it increases rapidly as
patch size decreases So, species from surrounding habitats often colonize the edges of
patches to compete with or prey on the species living there, edge effects.
Species that are lost from small habitat fragments are unlikely to become re-established there
because dispersing individuals are unlikely to find isolated fragments.
BUT species may persist in a small patch if it is connected to other patches by corridors of
habitat through which individuals can disperse.
Overexploitation has driven many species to extinction
Elephants and rhinoceroses are threatened in much of Africa and Asia b/c poachers kill them for
their tusks and horns.
The use of animal parts in traditional medical practices is a threat to some species. Invasive predators, competitors, and pathogens threaten many species
People have moved many species to regions outside their original range, deliberately or