Peter H. Raven
Director, Missouri Botanical Gardens
pinions vary widely on the numbers of people that individual areas, or
the world as a whole, can support, and objective analyses of the relationships
that exist between population and the environment are few and far between.
In view of this lack of readily available, clearly presented information,
this volume fills an important void. Its graphics, analyses and discussions
of individual ecosystems provide the kind of basis that any educated person
would like to have in approaching this subject or in acting intelligently
in many areas of modern life. It is thus a most welcome contribution to
the growing body of literature about the environment, focusing exclusively
on what is clearly the key area of concern.
As our numbers continue to grow, with increasing pressure on the environment
everywhere, it becomes more and more important to understand in as much
depth as possible the many and diverse aspects of this set of relationships.
In this volume, you will find them laid out in a way that is graphically
appealing, clear, consistent with contemporary thought on the issues and
readily accessible to the intelligent lay person. In doing so, the book
makes a contribution that is exceedingly timely, one that will lead to
further analyses and reflection on the part of individuals, governments
and corporations, as the authors have clearly intended.
Although it has long seemed obvious that there is an important linkage
between such factors as human population density, rate of growth, consumption
and the choice of particular technologies on the one hand, and the state
of the environment on the other, the quantitative analysis of such relationships
has by no means been adequately pursued, and they are often poorly understood
and represented. For these reasons, it is of great importance to make
what we do know accessible to both specialist and broader audiences, as
a basis for developing theory further and for making the best decisions
we can now. Although it is difficult to view the pertinent facts clearly
and without bias, it is evident that no relationships are more important
for us to understand as we strive to create a sustainable world for the
21st century and beyond. General statements, speculation and intuitive
deductions about the impacts of various aspects of human population on
the environment are no longer sufficient as a basis for effective action,
and additional empirical evidence and analyses are badly needed. This
book does not attempt such analyses, but rather endeavors to establish
a common base of understanding about what is known in this area. In doing
so, it makes an important contribution.
In its opening chapters, this book illustrates the various ways in which
population factors, such as rates of growth, absolute growth, consumption,
migration and the application of various technologies, affect both in
the short term and more enduringly the health of the worlds ecosystems.
Here, Paul Harrison presents an overview of exceptional clarity concerning
the relationship between population dynamics and the environment. This
treatment does not represent original research, but rather is a presentation
of contemporary thinking and data. The extensive use of graphics makes
every page a rich source of easily understood facts and figures about
the central relationships that this book explores.
The balance of the book presents an extensive series of analyses of individual
habitats throughout the world, considering in depth what is known about
the ways in which they are impacted by pressures associated with population.
This is a feature that will provide useful insights in many areas and
for many different people.
One of the most difficult aspects of providing sound analyses of these
relationships in the past has been the difficulty of linking the social
and natural sciences. Here, however, we find the issues presented in a
multidimensional fashion, demonstrating the cross connections between
human and natural environmental factors in determining a particular outcome.
In such an area, the AAAS, which brings together the wide array of all
the sciences, has a comparative advantage, and is particularly suited
to undertake interdisciplinary studies.
Where do we stand in our efforts to achieve a sustainable world? Clearly,
the past half century has been a traumatic one, as the collective impact
of human numbers, affluence (consumption per individual) and our choices
of technology continue to exploit rapidly an increasing proportion of
the world's resources at an unsustainable rate. Ehrlich and Holdren's
IPAT relationship, discussed in the second chapter of this book, lies
at the heart of understanding the population-environment relationship
and needs to be understood both in terms of the amount of resources necessary
to produce each unit of consumption, and also the amount of waste or pollution
generated in the process. At any event, during a remarkably short period
of time, we have lost a quarter of the world's topsoil and a fifth
of its agricultural land, altered the composition of the atmosphere profoundly,
and destroyed a major proportion of our forests and other natural habitats
without replacing them. Worst of all, we have driven the rate of biological
extinction, the permanent loss of species, up several hundred times beyond
its historical levels, and are threatened with the loss of a majority
of all species by the end of the 21st century.
As George Schaller, the noted conservationist, has put it, "We cannot
afford another century like this one" (i.e., the 20th century). As
the new millennium begins, human beings are estimated to be consuming
directly, wasting or diverting more than 40 percent of the total net terrestrial
photosynthetic productivity, and to be using about 55 percent of the world's
renewable supplies of freshwater. Median World Bank estimates, however,
have the human population increasing by another 50 percent over the next
half century, before leveling off at perhaps 10 billion people by the
year 2100. Trends over the past decades, which indicate a slowing in overall
population growth, support these projections, but it is clear that our
population will not, in fact, reach stability unless we find effective
ways to continue to address growth and to achieve goals that we have selected.
At the same time, levels of consumption are rising throughout the world,
even though it has been estimated that if everyone in the world were to
live in the way we do in the United States, it would require three more
planets comparable to Earth to support them. The notion that development
will eventually lead all of the world's people to achieve standards
of consumption comparable to those enjoyed in our country, using the technologies
we have available now, is clearly inaccurate; and yet it implicitly underlies
many of our actions, thoughts and aspirations. We live in a world in which
the World Health Organization considers that half of us are malnourished
at some level, taking into account vitamins, minerals and calories, and
one in which one in four people survives on less than a dollar per day.
It is not a world in which conditions will be improved by wishful thinking,
but only by concrete action, based on the kind of understanding that this
book will help to make possible.
The realization that the peoples of the world, rich and poor, are interdependent,
and that the rich have a responsibility to help the poor and that they
will need to do so in order to be able to achieve overall stability, is
a relatively recent one, coming into focus with the formation of the United
Nations following the Second World War, and especially with the 1972 Stockholm
conference on the global environment. Much has been written about these
matters over the past few decades, and when the nations of the world came
together at the Earth Summit in Rio de Janeiro in 1992, it was hoped that
effective action could be taken to address the complex needs involved
in building a sustainable world, and particularly the ways in which social
justice was necessary both morally and as a condition of forming such
a world. Day by day, this is becoming more important as more and more
people make larger and larger demands on relatively static types and amounts
In view of the complex relationships presented in the pages of this book,
it evidently is not feasible to estimate the Earth's carrying capacity
for people as an absolute. Rather, it is the complex relationship between
population density, consumption and choice of technology, together with
the choices that we make about the quality of life, that will determine
the number of people that an individual area, or the Earth as a whole,
can support sustainably. The diversity of our planet is decreasing rapidly,
and has done so dramatically for the past 400 generations, since crop
agriculture and the domestication of animals provided the means for building
villages, towns and cities, and gave rise to the complex human societies
in which the manifold activities that we call civilization take place.
The question that the relationships presented in this book bring into
focus is one of choice: what kind of world do we wish to have and to leave
for our children and grandchildren, all those who come after us. Human
populations will attain sustainability, but will it be sustainability
marked by dull, monotonous, unhealthy landscapes, or one in which the
biological and cultural riches that we enjoy in the early years of the
21st century will be maintained and enhanced, sources of material and
spiritual enrichment for everyone?
In making the many choices involved in constructing the world of the
future, we must go far beyond the mechanical calculations of an Adam Smith
to the vision of a Gandhi, who said, "The world contains enough to
satisfy every man's need, but never enough for our greed." It
is absolutely necessary to adopt a spiritual approach if we want the world
of the future to be a nurturing one, filled with variety of all kinds;
but it is not sufficient to have such an attitude to understand what we
must do to achieve this goal. In order to do so, we must understand the
relationships that are so well presented in the present volume in a way
that will inform the debate for years to come.
One puts down this book feeling a debt of gratitude to the authors, editors
and those who prepared the illustrations for the enlightenment and feeling
of rational hope that they have conveyed by laying out the realities of
the all-important population-environment relationship so clearly, comprehensively
and well. In order to build a better, more prosperous and healthier life
for our children and all those who will come after us, we all badly need
the kind of clarity of understanding that this very welcome book represents.
Given that understanding and our commitment to deal effectively and well
with our own future, we shall certainly be able to succeed beyond our
most optimistic assumptions.
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