Introduction to Biogeography and Conservation Biology

What is conservation Biology?
Conservation Biology came into existence as a distinct
discipline in the 1970's when biologists began to
describe the current scenario as a "biodiversity crisis".
Extinction rates were seen to match those during
megafaunal extinctions, e.g. the dinosaurs during the
The journal Conservation Biology was only created in
1987 and the Society for Conservation Biology was
founded in 1985.
Conservation biology arose from two opposed views
of nature and our relationship to it.
1. The Romantic-Transcendental Conservation
Ethic – from the writings of Ralph Waldo
Emerson, Henry David Thoreau, and John Muir.
Nature viewed in a quasi-religious sense and as a
way to ‘cleanse the human soul. The tradition
continues today in the Sierra Club.
2. The Resource Conservation Ethic – from Gifford
Pinchot, this is the basis of much of the activities of
government agencies like the Forest Service. It is
anthropocentric, and views nature as resources to
be used wisely.
The two opposing views have been joined in a third
view. This view predominates in Conservation
Biology today. It is called…
The Evolutionary-Ecological Land Ethic – Aldo
Leopold is its source, clearly presented in A Sand
County Almanac (1949). However, unlike Leopold,
modern ecology/conservation biology views
ecosystems in a non-equilibrium context.
Why is earth undergoing ‘megafaunal extinction’
rates? The reason: areas of greatest diversity, e.g.
tropical rain forest and coral reefs, are also areas with
the greatest numbers of as yet undescribed species
and simultaneously under severe pressure from
human activities.
Conservation biology is the scientific study of how to
maintain diversity with increasing human population
size and development. It is a synthetic science, built
from ecology, population biology, population
genetics, biogeography, economics, anthropology, and
philosophy with the intention of developing
principles and strategies to preserve diversity.
Here is why scientists worry about human impact.
It’s a graphical depiction of our ecological footprint,
i.e. human population density and degree of
transformation of natural habitats…
A more complete view of how interdisciplinary
conservation biology is:
The main objectives of Conservation Biology are:
• to investigate human impacts on global diversity
• to develop practical approaches to promote human
development without extinguishing biological
Here’s another view of the basic principles, this one
from a different introductory text by Primack (1994):
• Diversity of organisms is good; humans generally
value and appreciate biodiversity. Human-mediated
extinction of populations and species is bad.
• Ecological complexity is good and in many
instances mandatory to species survival. Harm to
one species may result in 'cascading' effects on
• Evolution is good.
• Biological diversity has intrinsic value.
There is another component in conservation biology,
necessary to understand parts of answers to HOW,
WHAT and WHERE for conservation. That subject is:
Biogeography is the study of the distributions of
species over space and time and the causes of those
It has two basic components: descriptive biogeography
and ecological biogeography. The first part studies the
geography of species and the second part deals in the
causes of those distributions.
To answer many questions in biogeography and
conservation biology we look to islands.
Island processes are seen as important in
understanding the population dynamics and genetics
of species having patchy distributions. Patchiness
characterizes the distributions of almost all species.
‘Islands’ include those in oceans or fresh water, lakes
in a terrestrial matrix, habitat islands, peninsulas,
clumps of zebra mussels on lakebeds of the Great
Lakes, and even patches in the distribution of species
scattered widely over an area. Island concepts help in
learning how to preserve species and communities as
humans impose themselves on natural environments.
It is important to see the history of a subject to
understand its development and future. So, here is a
short history of biogeography and conservation
Biogeography realistically began when it got past
simply describing and naming new species, and into
describing habitat characteristics, relationships
among species, i.e. how distributions were affected
by species interactions (competition, predation,
mutualism), history (site(s) of origin, dispersal
capabilities in relation to geological events,
ecological variability, climate (including climate
change), and continental drift.
The first attempts were phytogeography in the first
two decades of the 19th century. In 1805 Alexander
von Humboldt developed qualitative indicators of
relationships between plant species and climate.
That first classification was developed further,
particularly by DeCandolle in 1813. DeCandolle
divided botany into subdisciplines, separating out 1)
systematics and taxonomic description, 2) studies of
species interactions, particularly with man, and 3)
morphology, physiology and geography.
Not long afterward, Lyell proposed gradual change in
geographical features of the earth. He developed the
concept of uniformatarianism, the idea that processes
today are identical to processes operating in the past.
It is that concept that allows us to infer history from
observations made in contemporary time.
Darwin and Wallace, in their separate collecting trips
in the new world and southeast Asia respectively,
observed species distributions which were critical to
the development of the theory of evolution. They
used uniformatarianism to understand how some
aspects of these distribution arose.
Ernst Haeckel applied the theory of evolution to
species distributions directly. He named a special
discipline called chorology, which was the study of
the spatial distributions of organisms and their
causes. One of the major components explaining the
change in species' distributions was evolution, and
we now call the subject biogeography.
Alfred Russell Wallace, who should be credited as a
co-developer of evolution, is regarded as the father of
zoogeography. Because animals are mobile, and
because so long was spent simply categorizing
insects (because there are so many), 'animal
biogeography' took longer to get off the ground.
Wallace's master work, The Geographical
Distribution of Animals described the transition in
terrestrial fauna between Australia, with its associated
islands, and the islands extending out from southeast
Asia towards Australia.
Other lines have since been drawn to demark this
transition. Weber's line encloses the region in which
the mammalian fauna is exclusively Australasian, and
west of the Celebes, between Bali and Lompok, is
Wallace's line, which marks the outer limit of the
Asian (or Oriental) mammalian fauna. In the narrow
zone between these boundaries there is limited
mixing; the area is called Wallacea.
During the late 19th and early 20th centuries, a number
of important descriptive rules for animal
(particularly mammal) anatomy developed,
generally related to climates:
1.Bergmann's rule which states that warm blooded
animals from cooler climates have larger body
sizes and lower surface to volume ratios.
2.Allen's rule which says that warm blooded animals
will have more compact extremities in cold
climates than in warm ones.
In the same time frame, plant communities were
classified. Merriam classified altitudinal and
latitudinal vegetation types and zones, termed life
zones, and their relationship to temperature and
rainfall. Most modern diagrams of Merriam's
zonation present it as a three axis system, in which
the climatic axis is potential evapotranspiration.
Merriam attempted to generalize his classification
scheme to animals, and failed.
During the 20th century two major developments have
influenced the development of biogeography: the
recognition of continental drift and the development
of a quantitative theory of island biogeography.
Continental drift was first described by Wegener in
1912. Its acceptance took quite a while. Philip
Darlington published a monograph (The
Biogeography of the Southern End of the World) in
1957 that did not accept continental drift and created
‘fanciful’ explanations for relations among the
southern continents. He published a revision about a
decade later that used continental drift explanations.
Finally, we come to the quantitative theory of
biogeography, traceable to MacArthur and Wilson. It
is from quantitative biogeography that conservation
biology arose.
Human Impacts
Humans (native Americans and Inuit) are widely
regarded as responsible for the extinction of a variety
of large mammals in North America including
mastodons, tapirs, glyptodonts, and giant ground
Humans have long cut forests. In Greek times, the
forests of the Baltic area and those in southern Asia
were cut for ship building. Tropical forest has been
cut for centuries in the course of slash and burn
agriculture. The contemporary problem is the effect
of increased population size, meaning larger areas cut
and more frequent exhaustion of areas.
Candolle, A. de. 1855. Géographie botanique raisonée. 2 vol. Paris, Masson Editeur.
Clausen, Keck, and Heisey. 1948. Experimental studies on the nature of species. III.
Environmental responses of climatic races of Achillea. Carnagie Institute, Pub. no.581.
Darlington, P. 1957. Biogeography of the Southern End of the World. Harvard Univ.
Press, Cambridge, MA.
Hardin, G. 1968. The tragedy of the commons. Science 162:1243-1248.
MacArthur, R.H. and E.O. Wilson. 1963. An equilibrium theory of insular
zoogeography. Evolution 17:373-387.
MacArthur, R.H. and E.O. Wilson. 1967. The Theory of Island Biogeography.
Princeton Univ. Press. 203p., Princeton, NJ.
Groom, M.J., G. Meffe, and C.R. Carroll. 2006. Principles of Conservation Biology.
3rd ed. Sinauer, Sunderland, MA.
Primack, R.B. 1994. Essentials of Conservation Biology. Sinauer, Sunderland, MA.
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