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 organisms).
• Plants colonized the land, accelerating the weathering of rocks thus, gaining
access to rock-bound nutrients.
• Weathering of phosphorus increased global productivity = rise of oxygen
• Rise of vascular plants increased oxygen concentration; lower carbon dioxide
• Human beings cause extinctions of other species
o When first arrived in N. America (20 000 years ago), encountered a rich
fauna of large mammals.
o Most species were exterminated (overhunting) within a few thousand
• 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 single species.
• 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 services.
o Humans derive enormous aesthetic pleasure from interacting with other
o Extinctions deprive us of opportunities to study and understand
ecological relationships among organisms.
o Living in ways that cause the extinction of other species raises serious
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
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
• Species in imminent danger of extinction in all or a significant part of their
range are labelled endangered species.
• 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 risks.
• 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 local disturbances.
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
• 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
• 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
Invasive predators, competitors, and pathogens threaten many species
• People have moved many species to regions outside their original range,
deliberately or accidentally.