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Conservation biology means different things to different people. For
the purposes of this course, conservation biology covers all of those
topics that I have chosen to include in the course and none of those
topics that I haven't chosen to include. Seriously though, there are
reasons I chose the topics I chose to include. To understand what they
are, it may help to begin with a little history.
I don't think I have to convince anyone in this room that the world we
now live in is far different from the one that was here a few thousand
years ago. The reason for that difference is two-fold: the growth of
human populations and the enormous resource demands we make on
the planet.
- THE ENORMOUS INCREASE IN HUMAN POPULATION. The world had
fewer than 3 billion people in in when I was born.1 It reached 6 billion people in 1999. As
of last Thursday, the world population was nearly 6.8 billion
(http://www.census.gov/main/www/popclock.html;
Figure 1), and the increase has been faster than
exponential (Figure 2).
Figure 1:
Estimates of the total human population of the United States
and the world at 2:04pm EDT, 27 August 2009.
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Figure 2:
Human population growth over the last 10,000
years.
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- That's the bad news. THE GOOD NEWS IS THAT RATES OF
POPULATION GROWTH APPEAR TO HAVE SLOWED. The best guess from the
United Nation's population program is that world population will level
off at about 9 billion in 2050 (Figure 3). Of course,
9 billion people is a lot of people, and it means adding as
many people to the plant in the next fifty years as were alive when I
was born.
Figure 3:
Population projections for human populations through
2050.
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- THE ENORMOUS RESOURCE DEMANDS WE MAKE ON THE PLANET. Our
numbers alone would be enough to ensure a great impact, but we also
use many of the planet's resources. Peter Vitousek, Pam Matson, and
Paul Ehrlich [6] estimated over 20 years ago that
human beings capture over 40% of global net primary productivity,
meaning that we are responsible for consuming nearly half of the
annual energy input into the world's ecosystems. A more recent
attempt to estimate the same quantity [4]
emphasizes how little we now about our cumulative
impact. Nonetheless, the authors estimate that humans appropriate at
least 10% and possibly as much as 55% of terrestrial net
photosynthetic production (TNPP). Their best estimate is that we
appropriate about 32% of TNPP.
- But that's only the impact we have on net primary production. I
can't do it, but it's conceivable that someone smarter than I am
could imagine a scenario in which humans co-opt 50% of net primary
production without a significant impact on other inhabitants of the
earth. I can't come up with a sustainable scenario that allows us to
co-opt 50% of net primary productivity because of how much we've
already altered the face of the planet [7].
- 10-15% of the earth's land surface is occupied by row-crop
agriculture or by urban-industrial areas, and another 6-8% has been
converted to pastureland. Total affected: between 15 and 25%,
40-50% of land surface has been transformed or degraded.
- 22% of marine fisheries are overexploited or depleted, another
44% are at their limit of exploitation.
- Humans use about 50% of the runoff water that is fresh and
reasoably accessible. Human activities add at least as much fixed
nitrogen to terrestrial ecosystems as all other sources combined.
- Human activities are now responsible for fixing as much nitrogen
as all terrestrial nitrogen fixation by bacteria, and
anthropogenic nitrogen fixation is projected to increase by more
than 60% between now and 2050 (Figure 4).
Figure 4:
Current and
projected rates of annual nitrogen fixation due to human
activities [1]
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All in all, 83% of the earth's land surface has been directly
influenced by human activities (Figure 5), and
our impact is pervasive in densely populated areas like the
northeastern United States (Figure 6). Peter
Kareiva and colleagues point out that ``we have domesticated
landscapes and ecosystems in ways that enhance our food supplies,
reduce exposure to predators and natural dangers, and promote
commerce'' [3, p. 1866]
Figure 5:
The human footprint index reflects human population density,
land transformation, access, and electrical power
infrastructure [5]
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Figure 6:
The human footprint index clearly shows metropolitan areas in
the northeastern United States. In addition to Boston and New York,
which are labeled, it's easy to pick out Providence, RI, Hartford,
CT, Springfield, MA, Worcester, MA, and Portland, ME. If you know
the freeways in the area, it's not hard to pick out I-95, I-91,
I-90, and others. (See
http://sedac.ciesin.columbia.edu/wildareas/maps.jsp
for more
maps of the human footprint index.)
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The Millenium Ecosystem Assessment [1] summarizes the four
key findings of their study this way:
- Over the past 50 years, humans have changed ecosystems more
rapidly and extensively than in any comparable period of time in
human history, largely to meet rapidly growing demands for food,
fresh water, timber, fiber, and fuel. This has resulted in a
substantial and largely irreversible loss in the diversity of life
on Earth.
- The changes that have been made to ecosystems have contributed
to substantial net gains in human well-being and economic
development, but these gains have been achieved at growing costs in
the form of the degradation of many ecosystem services, increased
risks of nonlinear changes, and the exacerbation of poverty for some
groups of people. These problems, unless addressed, will
substantially diminish the benefits that future generations obtain
from ecosystems.
- The degradation of ecosystem services could grow significantly
worse during the first half of this century and is a barrier to
achieving the Millennium Development Goals.
- The challenge of reversing the degradation of ecosystems while
meeting increasing demands for their services can be partially met
under some scenarios that the MA has considered, but these involve
significant changes in policies, institutions, and practices that
are not currently under way. Many options exist to conserve or
enhance specific ecosystem services in ways that reduce negative
trade-offs or that provide positive synergies with other ecosystem
services.
In the United States, it is possible to recognize three different
responses to these problems. Groom et al. [2]
refer to these responses as ``ethics'' because each is intended to
provide guidance about how we should act and the choices we should
make with regard to our interaction with nature.
- THE ROMANTIC-TRANSCENDENTAL CONSERVATION ETHIC
In the mid-nineteenth century Ralph Waldo Emerson, Henry David
Thoreau, and John Muir waxed eloquent about the wonders of nature in a
mystical, almost religious language. Their writings convinced many of
the need to save wild places, regardless of whether those places
provide any direct economic benefit. The Sierra Club, which was among
the earliest of the formal conservation organizations, grew out of
Muir's efforts to protect Yosemite and other parts of the
Sierra Nevada.
- THE RESOURCE CONSERVATION ETHIC
In the late nineteenth century Gifford Pinchot, Teddy Roosevelt, and
others recognized that it was in our own best interest to protect at
least some portions of the natural world. Their motivation for doing
so, however, was that we derived important ``natural resources'' from
the earth. Unlike the philosophical conservationists, who hoped to
protect natural areas for their own sake, Pinchot and the utilitarians
hoped to protect natural areas for what they could do for us.
- THE EVOLUTIONARY-ECOLOGICAL LAND ETHIC
The most eloquent exposition of this approach is, of course, in Aldo
Leopold's A Sand County Almanac. It is, in many ways, a
synthesis of the preceding two. It lacks, mostly, the quasi-religious
overtones of Thoreau and Muir, and it lacks the strictly utilitarian
approach of Pinchot. Fundamentally, the land ethic recognizes that we
do derive benefits from nature, but the connectedness of ecological
systems means that it is difficult, if not impossible, to identify
only some components as useful.
The first rule of an intelligent tinkerer is to keep all
of the pieces. Aldo Leopold, The Round River
We'll return to a more complete discussion of these ethical issues in
the last lectures of this course. For now I just want to point out
that the first and third of these ethics are widely accepted within
conservation circles, but only the second has been persuasive to those
not already committed to conservation. As a result conservation
efforts, especially those prior to about 1960, were predominantly
either concerned with:
- Land conservation--setting aside parcels of land for
protection and public enjoyment or for scientific research, e.g.,
the NATURE CONSERVANCY.
- Wildlife conservation--management of game animal
populations to provide opportunities for hunting, fishing, and
observation, e.g., the AUDUBON SOCIETIES and the NATIONAL
WILDLIFE FEDERATION.
Interestingly, conservation efforts, at least until the early 1960's,
were almost entirely concerned with biological conservation.
In the 1950s and especially in the 1960s, these concerns broadened
into more general concerns about pollution and population (Rachel
Carson, Silent Spring; Paul Ehrlich, The Population
Bomb). Still, academic biologists in departments of botany,
zoology, or biology2 were little involved in providing advice to resource
managers charged with protecting endangered species or with managing
parks and nature reserves. Resource managers were trained largely in
departments of forestry, natural resources, and wildlife
management--departments whose faculty often had little contact
with colleagues doing basic research in ecology, evolutionary biology,
and systematics.3
In the late 1970s and early 1980s Mike Soulé and others in
traditional biology departments began describing the need for a field
of conservation biology that would take the basic principles of
ecology, evolutionary biology, and systematics and apply them to the
problem of saving endangered species. Soulé and Bruce Wilcox edited
a book, published in 1981, that those in traditional biologists often
regard as the founding document of the field.4 In the nearly twenty-five years since
Soulé and Wilcox a SOCIETY FOR CONSERVATION BIOLOGY has been
founded, programs in conservation biology have sprouted (often in
departments of forestry and natural resources) around the country, and
traditional biologists have shown increasing interest in the questions
conservation biologists pose. The focus of the field has also
broadened. Two broad strains can be recognized within it:
- Conserving endangered species--Demographic and genetic
consequences of small population size, population viability
analysis, biology of small popualtions, manipulative techniques that
enhance survival probability and design of nature reserves for
particular species.
- Conserving functional and structural aspects of important
ecosystems--Diversity and stability of ecological communities,
habitat fragmentation, landscape ecology, island biogeography, and
restoration ecology
More recently, we've come to realize that the idea that there's a
``nature'' out there separate from human influence is wrong. There are
degrees of human influence, or domestication as Kareiva et
al. [3] call it. The course roughly follows these
themes.
Next: The syllabus
Up: What is Conservation Biology?
Previous: What is Conservation Biology?
Kent Holsinger
2009-08-27