Table Of ContentModeling Dynamic Systems
Series Editors
Matthias Ruth
Bruce Hannon
Springer Science+Business Media, LLC
MODELINGDYNAMICSYSTEMS
ModelingDynamicBiologicalSystems
BruceHannonandMatthiasRuth
ModelingDynamicEconomicSystems
MatthiasRuthandBruceHannon
DynamicModelingintheHealthSciences
JamesL Hargrove
ModelingandSimulationinScienceand
MathematicsEducation
WallaceFeurzeigandNancyRoberts. Editors
DynamicModelingofEnvironmentalSystems
MichaelL DeatonandJamesJ.Winebrake
DynamicModeling,SecondEdition
BruceHannon andMatthiasRuth
ModelingDynamicClimateSystems
WalterA.Robinson
DynamicModelingforMarineConservation
MatthiasRuthandJamesLindholm. Editors
Formoreinformation,see:
www.springer-ny.com/biology/moddysys
Matthias Ruth James Lindholm
Editors
Dynamic Modeling
for
Marine Conservation
With a Foreword by Elliott A. Norse
With 212 Illustrations
EXIRA
MATERIALS
extras.springer.com
Springer
Matthias Ruth ]ames Lindholm
Environmental Program Stellwagen Bank National
School of Public Affairs Marine Sanctuary
Van Munching Hali 175 Edward Foster Road
University of Maryland Scituate, MA 02066, USA
College Park, MD 20742-1821, USA
Series Editors
Matthias Ruth Bruce Hannon
Environmental Program Department of Geography
School of Public Affairs 220 Davenport Hali, MC 150
Van Munching Hali University of Illinois
University of Maryland Urbana, IL 61801, USA
College Park, MD 20742-1821, USA
Cover photograph: Kelp beds are extremely complex and critical marine habitats. Wise
management of both kelp beds and the animals that depend on them is key to the
future of our marine ecosystem. OAR!National Undersea Research Program (NURP)
http://www.photolib.noaa.gov/nurp.
Library of Congress Cataloging-in-Publication Data
Dynamic modeling for marine conservation / editors, Matthias Ruth, ]ames Lindholm.
p. cm.
Includes bibliographical references (p. )
Additional material to this book can be downloaded from http://extras.springer.com.
ISBN 978-1-4612-6544-3 ISBN 978-1-4613-0057-1 (eBook)
DOI 10.1007/978-1-4613-0057-1
1. Conservation biology--Computer simulation. 2. Marine biological diversity
conservation--Computer simulation. 1. Ruth, Matthias. II. Lindholm, ]ames, 1968-
QH75 .D96 2001
333.91'6416'oOl3--dc21 2001032840
Printed on acid-free paper.
© 2002 Springer Science+Business Media New York
Originally published by Springer-Verlag New York Inc. in 2002
Softcover reprint of the hardcover lst edition 2002
AII rights reserved. This work consists of a printed book and a CD-ROM packaged with the
book. The book and the CD-ROM may not be translated or copied in whole or in part with
out the written permission of the publisher (Springer Science+ Business Media New York), except
for brief excerpts in connection with reviews or scholarly analysis.
Use in connection with any form of information storage and retrieval, electronic adaptation,
computer software, or by similar or dissimilar methodology now know or here-after
developed is forbidden. The CD-ROM contains the run-time version of the STELLA ®s oft
ware. STELLA® software © 1985, 1987, 1988, STELLA® software© 1985, 1987, 1988, 1990-1997,
2000, 2001 by High Performance Systems, Inc. Ali rights reserved. STELLA® is a registered
trademark of High Performance Systems, Inc.
The use of general descriptive names, trade names, trademarks, etc., in this publication, even
if the former are not especially identified, is not to be taken as a sign that such names, as
understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely
byanyone.
Production coordinated by Impressions Book and ]ournal Services, Inc., and managed by
Timothy A. Taylor; manufacturing supervised by]acqui Ashri.
Typeset by Impressions Book and ]ournal Services, Inc., Madison, WI.
987654321
ISBN 978-1-4612-6544-3 SPIN 10841610
Foreword
The oceans are shrinking.
They're not literally shrinking; warming in the last century has actually
expanded the sea enough to threaten low-lying coastal lands that are vul
nerable to storm surge. During the same interval, however, events on land
have increasingly affected the sea.Since in most ways the Earth isa closed
system-a zero-sum planet in today's parlance-as terrestrial influence on
the sea expands, the sea's influence on its own processes shrinks. Control
of many crucial marine processes no longer resides within the sea.
The evidence for this isabundant and, to anyone who islooking, unmis
takable. In recent decades scientists have witnessed unprecedented pertur
bations and increases in previously uncommon events that demonstrate
growing terrestrial influences on the sea. Numerous marine species, from
sea urchins to monk seals, have experienced devastating epidemics. The
numberof harmful algalblooms and jellyfishpopulation explosions isrising
An hypoxic "dead zone" in the Gulf of Mexico off the mouth of the
Mississippi Rivernow appears each year and grows toencompass an area as
largeas NewJersey. Live coral coverinshallow reefs inFlorida,Jamaica, the
Maldivesand many other locations has severely declined. Deepwater reef
building corals,once widely distributed,have disappeared throughout much
of their ranges. Researchers have discovered high concentrations of persis
tent organic pollutants in declining populations of beluga whales and polar
bears,both high trophic levelpredators inmarine food webs. Populationsof
once-abundant fishes, such as Atlantic cod in Newfoundland, Napoleon
wrasse in Indonesia and bluefin tunas throughout temperate seas, have
declined sharply. What is more, a new kind of disturbance occurring on a
continent-sized scale is converting the formerly tranquil seabed as deep as
2,000meters into a biological wasteland.
The common thread in all these and countless other cases is the un
precedented expansion in the population, technology and economic activ
ityof one terrestrial species. Humans are now so powerful that we are pro
foundly affecting the Earth'sbiogeochemical cycles and biological diversity.
Aswe have converted more and more of the terrestrial realm to suit our
v
vi Foreword
needs, we have increasingly harmed the sea. One reason isthat, in a geo
chemical sense, the sea is downhill from the land; far more nutrients and
toxics flow from land to sea than vice versa. Moreover, the sea is where
land-dwellers conduct the last great hunt for Earth's wildlife, our marine
fisheries.
Unfortunately, individuals, companies and governments seldom employ
the precautionary principle (essentially,"Don't act unless you can be confi
dent of doing no consequential harm") in dealing with the rest of the
world. Thus, deciding to cease and reverse harm requires an after-the-fact
understandingofhow we are affectingmarine processes.However, our un
derstanding is complicated by statistical confounding, the difficultyin un
raveling strands of cause and effectwhen many human activitiesare affect
ing the sea concurrently. For example, we know that North Atlanticright
whales are critically endangered even though whaling for them was
banned more than 60 years ago. But is this because undersea noise pre
vents them from finding mates, persistent organic pollutants reduce their
reproductive success, the food webs that support them have been altered,
they are experiencing demographic imbalances or inbreeding depression,
some other agent that we haven't yet recognized is harming them, or all
these factors in combination? In this and many other cases, itis difficultto
reach sound conclusions, yet we desperately needmore insight to protect,
restore and sustainably use the livingsea. In essence,humans are perform
ing a vast unplanned and uncontrolled experiment on our planet's life
support systems, and the fact that we are utterly dependent on their func
tioning for our survivalsuggests the value of tools that help us understand
key cause-effect relationships.
Modelingthe dynamics ofsingle populations, interacting species, ecosys
tems and human impacts is a powerful means of penetrating the haze
caused by multiple variables behaving in different ways. Modeling allows
marine conservationbiologists to describe components ofsystemsquantita
tivelyand to assemble them into larger systems whose complexity exceeds
our unassisted predictive capacity.Thus,itcan reveal results that we might
not readily infer, results whose assumptions can be examined, challenged,
modified and re-examined until they represent the broadest and deepest
understanding we can create. Once modeling was done in the realm of in
timidating mainframe computers and equally intimidating programming
languages. Now the exponential increase of computing power and access
to it has democratized modeling. At the same time, models have become
more realisticand user-friendly,allowing a growing number of established
scientists and students to use them to test hypotheses, explore dynamics
and weigh sensitivities.
Ofcourse,amodel isnot a panacea.Itisapotenttool inatimewhen the
questions facing us are dauntingly complex and policy makers require
timelyguidance. Amodel isasimplifiedvisionofnature, and itsvalidityde
pends on the degree to which it identifies, portrays and connects relevant
Foreword vii
variables accurately. In a world where manifold consequences of our ter
restrialspecies are effectivelyshrinking oceans and the rest of nature,mod
eling could be crucial to protecting, restoring and sustainably using ourliv
ing planet. The powerful yetaccessible modeling methods discussed in this
book are a welcome step forward in marine conservation biology.
ElliottA.Norse, President
Marine Conservation Biology Institute
October 17, 2000
Series Preface
The world consists of many complex systems, ranging from our own bod
ies to ecosystems to economic systems. Despite their diversity, complex
systems have many structural and functional features in common that can
be effectively modeled using powerful, user-friendly software. Asa result,
virtually anyone can explore the nature of complex systems and their dy
namical behaviorunder a range of assumptions and conditions.This ability
to model dynamic systems isalready having a powerful influence on teach
ing and studying complexity.
The books in this series will promote this revolution in "systems think
ing"by integrating computational skillsofnumeracyand dynamic modeling
techniques into a variety of disciplines. The unifying theme across the se
rieswillbe the power and simplicityof the model-building process,and all
books are designed to engage readers in developing their own models for
exploration of the dynamics of systems that are of interest to them.
Modeling Dynamic Systems does not endorse any particular modeling
paradigmor software.Rather,the volumes inthe series willemphasize sim
plicityof learning, expressive power,and the speed of execution as priori
ties that willfacilitatedeeper understanding ofsystems.
MatthiasRuthand Bruce Hannon
ix
Acknowledgments
Matthias Ruth and James Lindholm thank the Pew Charitable Trusts, the
Kendall Foundation, the Mudge Foundation, and the National Undersea
Research Center at the Universityof Connecticut for their support of work
on this book and research related to it.
Ms. Sara Schaub of the National Undersea Research Center at the Uni
versity of Connecticut contributed significantly to the preparation of the
glossary.
DevelopmentofChapter 10byAndrew M.Lohrerand RobertB.Whitlatch
was in part supported by a grant form the NationalScienceFoundation.
RoelofM.]. Boumans and Pamela M. Behm thank Dr. Frederick T. Short
and Dr. David M. Burdick of the Jackson Estuarine Laboratory (University
of New Hampshire) for their invaluable expertise in the field of eelgrass
ecology. They also thank the numerous students at the University of New
Hampshire who have contributed to this project.
Mark Maguire and Matthias Ruth thank Yamiery Vanessa Puchi for her
contributions to Chapter 11.
RichardLangton and SallySherman acknowledge the financial supportof
the state of Maine and the Sportsfish Restoration Actwhile conducting this
study.
Peter Austerwas supported by the National Undersea Research Center at
the Universityof Connecticut, Stellwagen Bank National Marine Sanctuary,
and the USGeological Survey.
Denise Johnston, Chris Soderquist and Donella Meadows wish to thank
the many people who have contributed to the project on which Chapter 18
reports. Rockefeller Brothers Fund, C.S. Mott Foundation and Wallace
Global Fund provided the funds necessary to research the system and build
the model. Special thanks goes to the many people who have shared their
time and expertise, particularly Jason Clay at World Wildlife Fund, Peter
Riggs at Rockefeller Brothers Fund, and John Ward at National Marine
Fisheries Service.
Matthias Ruth
James Lindholm
xi
Contents
Foreword v
Series Preface ix
Acknowledgments xi
Contributors xix
Part 1. Concepts and Techniques 1
1. Introduction 3
MATIHIAS RUTH ANDJAMES LINDHOLM
1.1 Dynamic Modeling for Marine Conservation 3
1.2 What Is Conservation Biology? 5
1.3 Why Marine Conservation? 8
1.4 What Is Dynamic Modeling? 9
1.5 Using Dynamic Modeling to Generate Consensus 12
1.6 Overview 17
1.7 Questions and Tasks 20
2. Modeling in STELLA 21
MAITHIAS RUTH ANDJAMES LINDHOLM
2.1 Basic Population Model 21
2.2 Closing a Model 27
2.3 STELLA's Numeric Solution Techniques 32
2.4 Sources of Model Errors 37
2.5 Guidelines for the Development
of a Dynamic Model 40
2.6 Questions and Tasks 41
3. Predator-Prey Dynamics 43
MAITHIAS RUTH ANDJAMES LINDHOLM
3.1 Humpback Whales and Sand Lance 43
3.2 Sectors 49
3.3 Questions and Tasks 53
xiii
