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Lecture

ENVB 2050 Lecture Notes - Conservation Biology, Species Richness, Ecosystem Services


Department
Environmental Biology
Course Code
ENVB 2050
Professor
all

Page:
of 5
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:
oEvolution is a process that unites all of biology.
oThe ecological world is dynamic.
oHumans 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
concentrations.
Rise of vascular plants increased oxygen concentration; lower carbon dioxide
concentrations.
Human beings cause extinctions of other species
oWhen first arrived in N. America (20 000 years ago), encountered a rich
fauna of large mammals.
oMost 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 single species.
That’s why now more and more people value biodiversity for many reasons:
oHumans depend on other species for food, fiber, and medicine
oSpecies are necessary for the functioning of ecosystems and its many
benefits and services.
oHumans derive enormous aesthetic pleasure from interacting with other
organisms.
oExtinctions deprive us of opportunities to study and understand
ecological relationships among organisms.
oLiving 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 extinctions:
oDo not know how many species live on Earth.
oDo not know where species live (i.e. animal ranges are poorly known).
oDifficult to determine when a species actually becomes extinct.
oDo 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 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
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 accidentally.
Some become invasivethey spread widely and become unduly abundant at a
cost to the native species of the region.
Invasive plants can have many negative effects on ecosystems: while native
plants must devote considerable energy to defending themselves against the
native herbivores. The invasive plants typically have high rates of growth and
reproduction b/c they invest less energy in producing defensive compounds.
Invaders tend to take advantage of soil nutrients in ways native plants cannot.
Rapid climate change can cause species extinctions
If the climate warms by only 1̊C, the average temperature currently found at
any particular location in N. America today will be found 150km to the north.
If the climate warms 2̊C to 5̊C, some species will need to shift their ranges by
as much as 500-800km within a single century.
Conservation biologists cannot alter rates of global warming.
Organisms that are able to disperse easily may be able shift their ranges are
rapidly as the climate changes, provides that appropriate habits exist in the
new areas.
If the earth’s surface warms as predicted, entirely new climates will develop,
and some existing climates will disappear.
New climates are certain to develop at low elevations in the tropics b/c a
warming of 2̊C would result in climates near sea level that are warmer than
those found anywhere in the humid tropics.
57.4 What Strategies Do Conservation Biologists Use?
Use data, concepts, and tools from a variety of disciplines.
Determine what factors are affecting species health and numbers; use that
information to devise a plan.
Protected areas preserve habitat and prevent overexploitation
Establishing protected areas is an important component of efforts to preserve
biological diversity; they serve as nurseries from which individuals disperse
into exploited areas, replenishing damaged populations.
How should we select the areas to be protected? Two important criteria are the
number of species living in an area (species richness) and the number of
endemic species.