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Do We Still Need Nature?
The Importance of Biological Diversity
By Anthony C. Janetos
Our reliance on the Earth's non-renewable resources of oil and other
fuel and non-fuel minerals is well understood by most people. Yet,
when caught in the tide of technological advances that seem to
dominate our everyday lives, we can easily forget the extent to
which the modern, industrial world still depends on the biological
world: on both the ecological systems that we have already learned
to manage, such as farms and orchards, and on those we have not.
A fundamental property of ecological systems is a certain mixture, or
diversity of living things: we cannot expect to find deer
or ducks in the wild in the absence of the interconnected web of
other plants and animals on which their lives depend. Biological
diversity, or biodiversity, is a term that is now
commonly used to describe the variety of living things and their
relationships to each other and interactions with the environment.
The notion of biodiversity encompasses several different levels of
biological organization, from the very specific to the most general.
Perhaps the most basic is the variety of information contained in the
genes of specific organisms, be they petunias or people. Different
combinations of genes within organisms, or the existence of different
variants of the same basic gene are the fundamental "stuff" of
evolution. At the next level is the variety of different species that
exist on the Earth: a concept that includes the relationship of
different groups of species to each other. Biodiversity also describes
the varied composition of ecosystems, and the variety of different
sorts of ecosystems that are found in regions of study that biologists
call landscapes.
It has been clear for some time that at all of these levels of
organization the rich biodiversity that has always characterized the
natural world is today declining. The extinctions or threatened
extinctions of many species are but the most visible and well-known
manifestation of a deeper and more far-reaching trend. What has
been less obvious to many people are the potential consequences of
these changes.
Our Dependence on Biodiversity
Our lives depend on biodiversity in ways that are not often
appreciated. A case in point is agriculture. Society has learned a
tremendous amount about techniques to maximize crop yields, both
in temperate climates such as the grain belt of the U.S. and Canada,
and in subtropical and tropical environments, where the "green
revolution" that gained initial momentum in the 1960s vastly
increased yields of rice and other crops. In both cases, the advances
relied in part on biodiversity, and specifically on the availability of
diverse strains of cereal grains capable of responding positively to
heavier applications of fertilizer. The need continues, for we are still
learning how to sustain tropical agriculture and to minimize adverse
environmental impacts of fertilizers and pesticides while maintaining
high yields, and how to sustain the highly-managed agro-ecosystems
on which we more and more depend.
Much of today's world is also dependent on wild resources, of which
the best known examples are probably marine fisheries. The
industrial nations of the world support large and technologically-
advanced fleets whose sole purpose is to harvest wild fish for human
consumption, either directly or indirectly as fishmeal for fertilizers,
cattle feed, and aquaculture. Averaged globally, people derive about
16 percent of their total animal protein from marine fisheries. Many
developing nations also support a combination of open-ocean fishing
industries and intensive coastal and local fisheries, upon which
coastal populations depend both for food and for their economic
livelihood. About a sixth of the world's population, much of it in the
developing world, derives more than a third of their total protein
from marine fisheries.
Our long-standing dependence on the natural world for wood is
another example that is still much in evidence around the world.
Only a small fraction of the timber that is cut in the U.S., for instance,
is harvested from plantations: most is taken from natural forests that
are not intensively managed. Worldwide, an even greater fraction
comes from trees grown in the wild: by far the most important
source is unmanaged or lightly managed forest stands. The use of
wood for fuel, while of little consequence in technologically advanced
countries like our own, is an abiding staple in many developing
nations, and the twin demands for shelter and fuel have led to
extensive deforestation in many parts of the world, such as
Madagascar and Indonesia.
Four out of every five of the top 150 prescription drugs used in the
U.S. have had their origins in natural compounds. An example is
aspirin--a derivative of salicylic acid which was first taken from the
bark of willow trees. Today aspirin and many other drugs are
synthesized more efficiently than they can be extracted from the
wild, but they were first discovered in naturally occurring
compounds, which then formed the basis for subsequent
improvement. The process of discovery still continues. For example,
taxol, a promising anti-cancer drug, was first extracted
from a tree found in the wild: the Pacific yew. The chemical
substance from which taxol came has since been discovered in close
relatives of that species, thus reducing pressures for harvesting what
is already a small population.
Other economic gains derive from our interaction with the natural
world, of which the best known example may be the economic value
of tourism. Much, although obviously not all vacation travel comes
under the rubric of "eco-tourism," driven by a desire to see and
experience the natural world. The total economic activity generated
by tourists of this kind has been recently estimated by the United
Nations at nearly $230 billion each year. Even on regional and local
scales, the revenue generated by tourism can be substantial, and a
major component of local and regional economies (Table 1).
Each of the activities cited above provides resources and economic
gains for citizens in all societies. Yet each is at risk due to the
continued erosion of the resource on which they are based, which is
biodiversity. In what follows we review what is known of the forces
that are reducing biodiversity and some of the possible consequences
of this loss, and suggest areas in which additional research and policy
analyses are most needed.
The Winds of Change
The recent Global Biodiversity Assessment of the United Nations
Environment Program (UNEP) has identified four major causes of the
present decrease in biodiversity, and a fifth which may yet prove to
be important.
Land Use
(See Figure
1)
Changes in how the land is used are probably the principal
contributor to the current decline in biodiversity. About 1 to 2
percent of the land surface of the Earth is now devoted to urban use,
but other changes in land cover and land use far exceed the direct
impact of the small fraction that is paved or developed for homes
and factories and other buildings. Homo sapiens has
already converted about a quarter of all the land surface to
agricultural uses. By some estimates we now appropriate directly or
indirectly about 40 percent of what biologists call the primary
production of the Earth's biota (the products of
photosynthesis on which all other life depends), and the percentage
that comes under our control in this way is increasing.
The pressures on terrestrial resources and land depend very much
on population growth and the demands of early stages of economic
development. Moreover, land acquisition, especially for agriculture
and forestry, focuses initially on those areas with the most fertile
soils and equable climates, which are often the areas of greatest
biological diversity.
Deforestation in the humid tropics is probably the best-known
current example of rapid land-use change. During the decade of the
1970s, vast areas of tropical forest in South America, Africa, and
Southeast Asia were cleared and converted to agriculture and other
uses. In the middle-to-late 1980s, the rates of deforestation in South
America slowed dramatically, largely due to economic and tax policy
changes in Brazil, but the pace of cutting in Africa and Southeast
Asia, though poorly quantified, remains high. Globally, the rate of
loss of tropical forests for the 1980s has been estimated at about 1
percent per year, but there is still considerable uncertainty. The
rates of extinction of local species that accompany these rapid
changes in land cover may soon be far in excess of what is found
today, reaching as high as 10,000 times the natural background
rate.
In the industrialized nations of the Northern Hemisphere the most
rapid and widespread conversion of forest to other uses took place
over the last several hundred years. In this time, much of the
northeastern U.S., for example, was deforested at least once, in
connection with the rise of agriculture and timber industries. But as
regional and national economies changed, many previously cleared
areas were left to return to their natural vegetation. As a result,
forests have reappeared in parts of the Northeast, and indeed the
country as a whole has probably gained forested land over the last
several decades.
The current trend of most concern with respect to tree-cover in the
U.S. is a shift to smaller parcel sizes. What once were continuously
forested landscapes are now a quilt of small patches of trees, criss-
crossed with roads, subdivisions, agricultural tracts, and a variety of
different land-uses and land-covers: a scene that is familiar to
anyone who has looked out an airplane window. The average size of
tree-covered parcels is smaller than was the case twenty, fifty, or a
hundred years ago, resulting in a landscape that is highly fragmented
and partitioned.
The difference in terms of the natural world is great, and several
studies now point with concern to the biological impacts of the shift
to less continuous landscapes. The known consequences of these
changes are reduced numbers of both plants and animals and a
greater possibility of the outright loss of some of them--when in
effect, they are painted into a corner with nowhere left for them to
go. The interweaving of favorable and unfavorable habitats also
curtails the ability of organisms to disperse, and makes
recolonization of distant areas more difficult.
An analogous pattern of fragmentation can be found in parts of South
America where deforestation was previously extremely rapid.
Although the amount of new cutting appears to have fallen from that
of previous decades, it seems to be increasing again in the rain forest
of the Amazon, and the deforested, newly colonized regions now
have their own distinctive appearance. Patchworks of active fields,
orchards, abandoned fields, second growth forest, and primary forest
are the norm. But the scene is ever changing through an interplay of
active use by initial colonizers, abandonment, partial recovery
through natural processes, and as then often happens, subsequent
re-use. Analyses of potential impacts on biodiversity that are based
on simple measures of deforested area can provide little more than
very general conclusions.
Deforestation is not the only land-use change of interest or concern.
Another with broad implications for biodiversity is the
intensification of agriculture and grazing on those lands that have
been traditionally devoted to these purposes. Of particular
importance for biodiversity are the secondary impacts of intensive
agriculture. Heavy applications of fertilizers and pesticides have the
potential of creating additional environmental problems as well as
affecting the abundance and viability of the other plants and animals
and micro-organisms in the same or adjoining areas.
The adverse effects of non-point-source pollution due to the run-off
of pesticides and herbicides from intensively-used fields are well-
known. In addition, because of the understandable tendency to put
the best land into production first, the expansion of agriculture into
less fertile areas typically requires heavier applications of chemicals,
more extensive site preparation, and other forms of more intensive
management. The typical result is increased chemical run-off to the
landscape, and with ensuing degradation, additional pressure for
expansion, and so on. It is such a cycle that has led to widespread
desertification in some parts of the world, primarily through
overgrazing that can be compounded by naturally occurring
droughts.
Over-exploitation
Many of the best documented cases of individual species being
driven to extinction or near-extinction by humans are those of over-
exploitation.
The passenger pigeon--a species that resembled the smaller,
mourning dove--was in the early 1800s the most abundant bird in
North America, and so plentiful that migrating flocks of a billion or
more individuals would darken the skies of parts of the eastern U.S.
for days at a time. By the end of the last century it had been hunted
to the brink of extinction, and in September of 1914, in a Cincinnati
zoo, the passenger pigeon disappeared forever with the death of the
last remaining bird. The American bison, or buffalo, of the Great
Plains was also nearly hunted out of existence in the same century,
and its larger, woods-dwelling relative was driven to extinction.
As many as a quarter of all the bird species in the world may have
similarly vanished in the course of the last 1000 years with the
expansion of human populations through the islands of the South
Pacific. The spread of early people through the New World, about
10,000 years ago, was probably responsible for the extinction of
many of the large mammals that were originally here: now-extinct
mammoths, sloths, and cave bears are known to have been hunted
by those who first walked through North and South America. The
same impact was felt by large mammals in Australia, New Zealand,
and Madagascar. The current and rapid loss of tropical hardwoods in
many regions due to high commercial demand, low rates of
successful replacement, and the long periods of growth necessary to
produce new, marketable resources has raised concern about over-
exploitation of some species, such as rosewood, although none of the
trees are known to have been driven to extinction.
Over-exploitation is also a major factor in reducing the natural
biodiversity of marine fisheries through major reductions in
populations, although again, no extinctions have been documented.
During the last two decades, the world has seen the collapse of a
number of marine fisheries. Some of these have recovered, but
others, such as the cod and haddock fisheries in the North Atlantic,
have not. Even for those that recover, the consequences of the
original over-exploitation on population dynamics and genetic
diversity are now only poorly understood. What is often apparent is
a systematic decrease in the size, and hence age, of the individuals
that are harvested. The selective loss of larger fish has significant
impacts on those that remain. If fertility is strongly related to body
size, as is the case for many fish species, over-exploitation not only
reduces the abundance of a species, but it may also make recovery
more difficult in systematically removing the most fecund
individuals. The ensuing consequences for overall ecosystem
functioning and biodiversity are as yet not well understood.
Whole ecosystems can also be affected by over-exploitation. For
example, a reduction in organic carbon and nutrients, including
phosphorus or nitrogen, as may occur in intensively farmed areas,
decreases the fertility of soils. When losses are severe, the resulting
depletion can lead to either more intensified use by adding more
fertilizers and then herbicides and pesticides to control weeds and
pests (in the cycle noted above), or to abandonment. If abandoned,
the land will probably not recover its original component of plant
and animal species because of the depleted nutrients. Through this
chain of happenings, an over-exploitation of the soil for agricultural
gain can have long term, negative impacts on the biodiversity of the
region.
Alien introductions
Introductions and invasions of alien species of plants and animals is
a long-recognized problem, as detailed in an earlier issue of
CONSEQUENCES. We have only limited ability to predict quantitatively
the results of any particular intruder, including its capability of
establishing a permanent, reproducing population. What is certain is
that some areas are by nature more susceptible. Continental forests
are reasonably resistant to newly introduced tree species, except in
cases where they have been disturbed by heavy cutting or partial
clearing. Native meadows and prairies, when disturbed, have also
proven particularly susceptible to intruders, as is the case for the
many grasslands around the world that have been converted to
pasture or cultivated land. For example, many of the now common
grasses in the intermontane western U.S. and southwestern Canada
are transported Eurasian weeds. These species were able to invade
and become established because the original perennial tussock
grasses were unable to support the intensification of grazing from
large-scale cattle ranching.
Freshwater lakes and streams have little immunity to invading
species. Alien plants or animals seem able to establish reproducing
populations relatively easily, and the new species often have
significant impacts on biotic composition, and on a variety of
ecosystem processes. Two examples of the kind of changes that can
result from even well-meant introductions are the purposeful
introduction of game fish to many lakes and streams throughout the
world that replaced native varieties, and the ecological havoc that
followed the introduction of the Nile perch in Lake Victoria in 1960
to benefit commercial fishing. In less than thirty years, the appetite
of the Nile perch, whose food is smaller fish, led to the extinction of
about thirty species of fish that were native to the lake.
In terrestrial ecosystems, the largest changes occur when the
intruder brings quite different traits from those of native species.
The best documented example is that of the introduction of the exotic
tree, Myrica faga, into Hawaii, which has resulted in large
changes in ecosystem dynamics. The significant difference, in this
case, was the ability of the introduced tree--a legume like peas and
beans and clover--to convert atmospheric nitrogen to ammonia, a
characteristic not previously present in those ecosystems. This ability
of the introduced tree increases the nitrogen content of soils, and
thus alters the raw materials on which many other plant species
depend.
Introduced species with characteristics that are not qualitatively
different from those of native species, can through force of numbers
have large and long-lasting effects on them. About 100 European
starlings were released in New York City in 1890-91 by a collector
bent on establishing all the birds mentioned in the writings of
William Shakespeare. The result, evident throughout the country
today, is a diminished number of many native American songbirds,
through competition for nest-sites, in which the aggressive and now
very abundant starling has been extremely successful.
Pollution and toxification
The widespread increase of various pollutants and poisonous or toxic
substances in the environment has had obvious local impacts on
biodiversity in acutely affected areas. In western industrialized
countries the more severe instances of air and water pollution are for
the most part now being addressed through regulation and clean-up.
In many developing nations, however, the financial resources needed
to correct acute pollution problems are not available, and air- and
water-borne pollution continue to pose great environmental
problems, including local reductions in the diversity of living
species.
In many parts of the industrialized world, long-term chronic
pollution of air, water, and soil pose problems that are difficult to
resolve and rectify. The degree to which chronic, low-level pollution
constitutes a risk to biodiversity is less clear than for acute
exposures, but several facts are worth noting. One is that the
transport of many pollutants has been surprisingly wide and rapid.
Organic compounds of chlorine such as DDT, for example, can literally
be found all over the world due to atmospheric transport, even
though many of these substances have long been banned in western
industrialized countries, and they often remain and accumulate in
parts of both terrestrial and aquatic food chains.
Another concern is that long-term pollution, at even low levels, can
affect whole ecosystems, with resultant impacts on biodiversity that
bring about additional changes in how ecosystems operate. The chain
of events through which central European forests have responded to
acid deposition is a ready example. There, the chronic deposition of
airborne acidic substances from industrial effluents affects both
chemical processes and essential microorganisms in the soil, lowering
the vitality of trees and ground-cover and making groundwater,
streams, and lakes more acidic.
A third concern is that pollutants in soils and ground water, once
introduced, remain there for a long time, due both to the chemical
stability of many of the compounds involved, and the extremely slow
rates at which ground water is circulated or exchanged. A fourth
arises through the fact that many insecticides work by a process of
mimicry--copying the behavior of vital hormones in the species they
are designed to attack. But hormones that regulate the physiological
functions of non-target species, especially the reproductive functions,
can also be mimicked by the same insecticides. This raises the
concern that the ever-increasing load of these compounds in natural
systems may impact wildlife in general, and even humans. The
recent discovery of prevalent reproductive anomalies in some forms
of wildlife, such as some frogs and toads, is believed by some
scientists to be due to hormonally active substances introduced into
the environment.
Climate change
Natural variations in climate are among the more important causes of
past changes in biodiversity, both locally and for the Earth as a
whole. The prospect of human-induced changes in the climate adds
new concerns, however, particularly if the rate of change should
prove as rapid as many now foresee.
Current projections of general circulation models imply rates of
change of the global climate system that exceed those of almost any
natural variation in the geologic past. These rapid changes in surface
temperature and other weather parameters could lead to severe
mismatches between regional conditions and the physiological
requirements of many plant species. Were the average surface
temperature to rise by several degrees C, that warming would
probably be followed by potentially large re-organizations of some
ecological communities. For example, some model simulations suggest
that with such a change, much of deciduous forest in the eastern U.S.
could be replaced by savanna-like vegetation, composed of mixtures
of open park land and grasses. Similarly, some forest ecosystem
models have suggested that rapid and extensive diebacks of certain
trees could occur over much of their current range. Were this to
happen, there would undoubtedly be an associated wave of changes
in the fauna as well.
By itself, a systematic change in predominant vegetation, which has
happened before in the geologic past, would not necessarily imply an
increase in the rate of species extinctions. At the same time, with
global warming some species will find less optimal habitat than
before, particularly in higher latitudes. Plants and animals that now
inhabit montane and alpine habitats--and which are there through
an evolved dependence on cooler temperatures and higher altitudes-
-may with warming of these regions have nowhere else to go. The
combination of potentially rapid climate change with the increased
fragmentation of land cover is especially troubling: while it would be
conceivable for some organisms to disperse to climatically more
favorable habitats, the shift could in practice carry them across many
unfavorable regions.
The recent consensus findings of the Intergovernmental Panel on
Climate Change of a now detectable signature of anthropogenic
influences on the physical climate system adds new impetus to
examine the probable impacts of continued global warming on living
things, and biodiversity in particular.
The Loss of Species
Species extinctions have received the lion's share of the attention in
debates regarding biodiversity and the need to sustain it. The loss of
individual species in ecosystems, such as frogs in wetlands or ferns
in a forest, can certainly affect the ways in which those systems
work together to cycle essential nutrients and water and process
energy. Since we have only limited ability to predict how ecosystems
will respond in terms of replacement or built-in redundancy to the
possible loss of a specific species, there is some reason to be
concerned when any are threatened by extinction.
At the same time, the same degree of concern should apply to
reductions in the populations of species, even if they are not reduced
to disappearance altogether. The role that classes of organisms play
in ecosystems depends not only on what they do in terms of material
cycling and energy flow, but on how many are there to do it.
Reductions in abundance of an essential species can clearly affect
overall system functioning, and therefore the degree to which
ecosystem services will continue to be provided.
Some, known as keystone species, play a role in
ecosystems that seems out of proportion to their number, such that
even small changes in their abundance may have great impacts on
the ecosystems in which they live. A common example is the sea-
otter, a marine mammal that lives along the coasts of the northern
Pacific Ocean. They dive and prey on sea-urchins that principally
feed, in turn, on large seaweed called kelp. When sea-otters are
present, the number of urchins is kept sufficiently low that stands of
kelp--which are of commercial value as a source of potash and
iodine--can become established and thrive. When otters vanish from
the scene, the resulting growth in urchin populations effectively
prevents the plant's successful regeneration, and eventually leads to
the loss of kelp forests.
In time, all classes of living things--like the dinosaurs, or, we must
presume, our own species--must face extinction. But the
disappearance of any of them is a critical endpoint, marking the end
of 3.5 billion years of evolutionary development. In Nature it
represents a permanent depletion of biodiversity and a loss of
genetic information on which evolution is based. In terms of people
and nations, it counts as a loss of potential economic value in terms
of services or products. Each species is a reservoir of unique genetic
information that cannot be reproduced once it is gone. In this
broader sense, any extinction, however trivial it may seem,
represents a permanent loss to the biosphere as a whole.
What we need to know for informed policy decisions are the
ecosystem services that a threatened species provides; the degree to
which it offers opportunities for direct economic benefit; how
expected benefits weigh against costs of preservation; and on a more
general level, how present or expected rates of extinction compare to
what might be expected through natural changes. The telling
questions are whether and by how much the present rate of species
loss differs from the rate that Nature would exact, were we not here,
and whether the species that are lost play important keystone roles.
The challenge is that this sort of information is only rarely available.
Nor do we have, as yet, a predictive theory of keystone species.
Rates of loss
The UNEP Global Biodiversity Assessment has recently reviewed the
methods that have been used in the literature to calculate natural, or
background extinction rates and have compared them against
current trends. The results, which are intentionally conservative, are
sobering. Best estimates are that current extinction rates for well-
documented groups of primarily, but not exclusively, vertebrates and
vascular (in general, seed-bearing and fern-like) plants
are at least 50 to 100 times larger than the expected natural
background. There is no good reason to expect these rates to differ
very much for plant or animal groups that are less well-studied.
On the basis of recent estimates of land-use change, largely in the
tropics, there is a reasonable expectation that extinction rates in the
very near future could rise, worldwide, to as much as 10,000 times
the natural level. Extinctions of this number and extent would
approach, and possibly surpass, the major mass extinctions of the
geologic past, as when dinosaurs and other life forms disappeared,
about 65 million years ago.
The total number of species that inhabit the planet is unknown. The
UNEP Global Biodiversity Assessment uses an estimate of about 13
million, but the range varies from 8 to 50 million or more. Only about
2 million species have been described scientifically, and they are
distributed very unevenly among different taxonomic groups (Table 2).
While important in its own right, the number need not be precisely
known to be concerned about the rates at which the better
documented species are now disappearing. In today's world, most
extinctions will occur before the species have even been named and
described, much less known ecologically.
The Services that Biodiversity Provides
Assessments of the economic benefits of biological diversity have
been based primarily on our ability to generate revenue from
biodiversity, through activities that produce measurable results in
current markets, such as pharmaceuticals or tourism. But there are
additional benefits from biodiversity that are not so easily included
in commercial market analyses, and that come under the name of
ecosystem services. These are the end results of natural biological
processes that either improve the overall quality of the environment,
or provide some benefit to the human users of the landscape--such
as improvement of water quality and reduction of flooding. The
concept of ecosystem services is unabashedly tilted
toward human uses.
The study of ecosystem services is relatively new, but what is known
points consistently in one direction: maintaining diversity on a
variety of levels of ecological and biological organization--within
forests, or among the trees that are there, or even within the genes
of a single variety---is critical if services are to be maintained on a
sustainable basis.
Ecosystem services can be provided in a variety of forms. One
example is the purification of water that generally occurs by flowing
through forested ecosystems and wetlands, which is an extremely
important function from the standpoint of human populations that
live downstream. The presence of living vegetation provides an
efficient sink for many atmospheric pollutants as well. The regulation
of stream flow by vegetation in the upper reaches of watersheds has
long been recognized as an important ecosystem service, and
watershed managers manipulate both the amount and type of
vegetation in watersheds to help control sedimentation, floods, and
sometimes stream flow.
The services that ecosystems provide often depend on the
underlying physical structure of the habitat, such as the conditions
for feeding and breeding that may be needed for the continued
survival of an important animal species. What is often required is a
diversity of habitats over an entire landscape. Ecosystem services
may also depend on the presence of a particular species, as is the
case in highly co-evolved plant-pollinator systems, or in highly
managed agroecosystems that rely on specific pollinators, such as
honeybees.
Biodiversity also plays an important role in maintaining ecosystem
services over long periods of time, through the ups and downs of
natural variations. Ecosystems that have lost either genetic or species
diversity are less resistant to the effects of environmental
perturbations, such as droughts, and are slower to recover when
disturbed. Diversity is a form of ecosystem health insurance: those
ecosystems that include several species that serve the same or
similar functions tend to be more resistant to environmental stress
and recover faster from perturbations.
The Economic Value of Ecosystem Services
The economic value of ecosystem services is difficult to calculate, and
this raises several important problems when we look at biodiversity
in the context of public policy. How can we measure the economic
value of ecosystem services such as water purification, or resistance
to environmental disturbances? Since the maintenance of
biodiversity involves choices and ultimately, costs, how can markets
reflect and distribute these values appropriately?
The task may be somewhat easier in the case of new products and
materials that are derived from the natural world. Prospecting for
new pharmaceuticals is the most publicized, but not the only
example. New food crops are also a possibility, although to date there
have been very few such introductions that have achieved more than
regional importance, either dietarily or economically. More
intriguing, perhaps, is the use of genetic engineering to extract
biochemical processes from the natural world. Research of this kind
has found application in biological clean-up, or
bioremediation of toxic waste and oil spills. An even
more promising and somewhat more controversial opportunity is
found in harnessing processes at the most fundamental levels of
biological structure.
The pool of resources hidden in the genetic resources of living things
is potentially huge. An example is the polymerase chain
reaction (PCR) that is used in genetic research and in
commercial applications to manipulate DNA. The ready availability of
substances that speed up the rate at which the cells replicate--the
catalysts that in living matter are proteins known as enzymes--has
literally made genetic engineering practical on industrial scales.
The enzymes used to catalyze PCR were first isolated from bacteria
that can survive only in high temperatures, and the source from
which they were taken was natural hot springs in Yellowstone
National Park. In this case, to say that an entire new industry
depended on the diversity of organisms and habitats in the National
Park system is no exaggeration. Substantial prospecting is now
underway in these and other extreme environments to find enzymes
that will catalyze other, industrially-useful reactions.
What Lies Ahead?
The population of the Earth will likely double by the year 2050,
resulting in a world of at least 10 billion people, the largest number
of whom, by far, will live in tropical and subtropical Asia, Africa, and
South America. These are as well the regions in greatest need of
economic development, and the twin pressures of population growth
and economic expansion can only increase the demands on biological
resources. We can anticipate an ever-increasing competition among
different uses of the available land, and the maintenance of
biodiversity may not rank high in the face of other, more obvious
demands.
Many of the existing policies of our own country that have been
enacted to preserve biodiversity have been focused on threatened
species, or to preserve striking or unique ecosystems, such as
Yellowstone National Park. The Endangered Species Act, the
Convention on International Trade in Endangered Species, and our
system of National Parks will continue to help in preserving
biodiversity. But there are other areas of public policy that are as
useful and important. In fact, it may well be that lands and waters
that are necessarily exploited for their natural resources will hold
the key for practical strategies to maintain biodiversity, for parks
and preserves, alone, are inadequate for the task.
In truth, much that happens to preserve or decrease biodiversity
arises through secondary effects of policies that are enacted for other
reasons. Fisheries policies that aim to maintain fishery harvests;
forestry policies that seek to maximize the economic yield of
marketable timber; agricultural policies that maintain subsidies for
keeping land in production that might be used for other beneficial
purposes; and policies for the management of public lands that
encourage overgrazing by maintaining artificially low grazing fees all
have important negative effects on biodiversity, although not by
design.
Other existing policies have impacts that work in the other direction.
But unless the impacts on biodiversity of private acts or public
policies are understood, and until there exists a broader consensus
regarding the relative value of biodiversity, there is little hope, in
this or any country, of holding the line at the levels that are needed
for almost any use or service. We all need to be more aware of the
direct benefits, indirect benefits, services, and future potential that
biodiversity offers for both private gain and public benefit. We need
greater awareness and coordination of policies that affect
biodiversity, and national goals that go deeper than the protection of
endangered species and the preservation of public parks.
From an economic perspective, much more work needs to be done to
put a fair and meaningful valuation on biodiversity. The service
aspects of biodiversity must be understood, and market mechanisms
put in place to include these very real factors in both policy and
business decisions.
From a scientific perspective, we need to learn more, and more
quickly, about the role that biodiversity plays in the working of
ecosystems. Gaps in our present knowledge of these connections now
limit our assessments of the risks imposed when biodiversity
declines, and preclude more complete economic evaluations.
In all of this, calls will be heard to defer action until we have in hand
a more complete and reliable inventory of the present extent and
variety of life on Earth, in terms of the number of species of plants
and animals. Although counting must go on, it is now clear that
waiting to learn the full extent of biodiversity before acting to stem
so precipitous a decline is not a prudent choice, for both ecological
and economic reasons.
Last, but certainly not least, are the issues of stewardship and ethics.
In the long run, we must be concerned about maintaining the
capability of the biological world to adapt, through adjustment and
evolution, to changes in the physical environment. In addition, many
would agree that as a society we bear the ethical obligation to protect
the habitability of the planet, and to act as responsible stewards of
its biological riches for the present and future welfare of the human
species. To do that requires an appreciation of the value of
biodiversity--both what it provides for the natural world and the
ways that we can use it--and a commitment to preserve it so that
our children and their children will continue to realize the benefits of
a biologically rich Earth. Surely such a challenge demands the
attention of scholars and policy-makers alike.
Reviewers
Dr. Thomas Lovejoy is an ecologist and widely-known expert
on biological diversity at the Smithsonian Institution in Washington,
D.C., where he serves as Counselor to the Secretary for Biodiversity
and Environmental Affairs and as Director of the Smithsonian's
Institute of Conservation Biology.
Dr. Gordon Orians, an ecologist, is Professor Emeritus of
Zoology at the University of Washington in Seattle, a Past-President
of the Ecological Society of America, and a member of the National
Academy of Sciences. For many years he has contributed to the
science-policy interface through the Science Advisory Board to the
EPA, the National Research Council, the World Wildlife Fund, and the
Smithsonian Institution.
Scientific reviewers provide technical advice to the authors and
Editor, who bear ultimate responsibility for the accuracy and balance
of any opinions that are expressed.
For Further Reading
Biodiversity, edited by E. O. Wilson. Contributions
from a National Forum on BioDiversity. National Academy Press,
Washington, D.C., 1988, 521 pp.
Global Biodiversity Assessment, Policymakers' Summary,
United Nations Environment Programme, 1996.
The National Biological Service homepage
at http://www.its.nbs.gov/ [now the USGS's Biological Resources Division]
The Diversity of Life by E. O. Wilson,
Harvard Univ. Press, Cambridge, Mass., 1992, 424pp.
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