Causal Factors for Wetland Management and Restoration: A Concise Guide

163 Pages·2023·8.801 MB·English

by  Paul A. Keddy

Wetlands: Ecology, Conservation and Management 8
Paul A. Keddy
Causal Factors
for Wetland
Management
and Restoration:
A Concise Guide
Wetlands: Ecology, Conservation and
Management
Volume 8
Series Editor
C. Max Finlayson, Albury, NSW, Australia
Editorial Board Members
Cui Lijuan, Institute of Wetland Research, Chinese Academy of Forestry,
Beijing, China
Anne A. van Dam, Dept. of Water Resources and Ecosystems, IHE, Inst for Water
Education, Delft, The Netherlands
Siobhan Fennessy, Kenyon College, Gambier, OH, USA
Patricia Kandus, Instituto de Investigaciones e Ingeniería Ambiental, Universidad
Nacional de San Martín, San Martin, Buenos Aires, Argentina
Julius Kipkemboi, Department of Biological Sciences, Egerton University,
Egerton, Kenya
Donovan Kotze, Centre for Water Resources Research, University of KwaZulu-
Natal, Pietermartizburg, South Africa
Ritesh Kumar, 2nd Floor, Wetlands International South Asia, New Delhi, India
Tatiana Lobato de Magalhães , Autonomous University of Queretaro, Santiago
de Queretaro, Querétaro, Mexico
Victor Marin, Departamento de Ciencias Ecologicas, Universidad de Chile,
Santiago, Chile
Beth Middleton, U.S. Geological Survey, Lafayette, LA, USA
Randy Milton, Dept of Natural Resources, Acadia University,
Wolfsville, NS, Canada
Simon Mitrovic, School of Life Sciences, University of Technology Sydney,
Ultimo, NSW, Australia
Nidhi Nagabhatla, Institute for Water, Environment Health, United Nations
University Institute on C, Brugge, Belgium
Kerrylee Rogers, School of Earth & Environmental Sci, Univ of Wollongong,
Wollongong NSW, Australia
Rebecca Woodward, 35 Percent, Chalford, UK
The recognition that wetlands provide many values for people and are important
foci for conservation worldwide has led to an increasing amount of research and
management activity. This has resulted in an increased demand for high quality
publications that outline both the value of wetlands and the many management steps
necessary to ensure that they are maintained and even restored. Recent research and
management activities in support of conservation and sustainable development
provide a strong basis for the book series. The series presents current analyses of the
many problems afflicting wetlands as well as assessments of their conservation
status. Current research is described by leading academics and scientists from the
biological and social sciences. Leading practitioners and managers provide analyses
based on their vast experience.
The series provides an avenue for describing and explaining the functioning and
processes that support the many wonderful and valuable wetland habitats, such as
swamps, lagoons and marshes, and their species, such as waterbirds, plants and fish,
as well as the most recent research directions. Proposals cover current research,
conservation and management issues from around the world and provide the reader
with new and relevant perspectives on wetland issues.
Paul A. Keddy
Causal Factors for Wetland
Management and
Restoration: A Concise
Guide
Paul A. Keddy
Independent Scholar
Lanark County, ON, Canada
ISSN 1875-1261 ISSN 1875-127X (electronic)
Wetlands: Ecology, Conservation and Management
ISBN 978-3-031-21787-6 ISBN 978-3-031-21788-3 (eBook)
https://doi.org/10.1007/978-3-031-21788-3
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Preface
For some years I have been teaching and writing about the causal factor approach to
wetland ecology. My intention in doing so was to provide a logical and consistent
structure for the science of wetland ecology. I have received a good deal of positive
feedback on the virtues of this approach, and I used it in my textbook, Wetland
Ecology (DOI: https://doi.org/10.1017/CBO9780511778179).
An environmental planner in China told me that my book Wetland Ecology was
“overwhelming.” I thought there was some wisdom in that observation. I had writ-
ten Wetland Ecology for fellow scientists and university students, who would expect
a good deal of detail, many references to scientific papers, and multiple examples.
This got me wondering: just how short could a guide to wetland ecology be?
Consider the audience of park managers, landscape architects, consultants, plan-
ners, and engineers who might be sincerely interested in protecting and restoring
wetlands, but might not have the time to read Wetland Ecology. Could I write a
concise guide for them?
In this book, therefore, I have kept referencing to a minimum. If there are state-
ments that seem insufficiently referenced, I invite you to consult Wetland Ecology
for a more complete story.
I have also kept examples to a minimum, mostly just two or three per section. In
Wetland Ecology, I often have five or more examples, so again, if this is too short for
your tastes, I recommend the larger book. I have kept what we might call classic
examples in wetland ecology. Some people are of the impression that new work is
always better, and I have even heard that some professors tell their students not to
read work that is more than 5 years old. I disagree. I have kept “old” examples
including peat bog succession (Dansereau and Segadas-Vianna 1952), changes in
deltas with time (Penland et al. 1988), and effects of fire in the Everglades (White
1994). These are fine work that is still useful today. Throwing them out would be the
same as throwing out a perfectly useful antique chair only to replace it with a new
plastic one. We need to keep good work in circulation, and it remains useful for
teaching students about landmarks in the development of wetland ecology. (I will
note, too, that older work often has better artwork than modern work. Clip art is not
a substitute for a talented pen and ink artist.)
v
vi Preface
Another book hovers in the background. The causal factor approach in this book
has a broader theoretical context—the pool and filter approach to community ecol-
ogy—so, those of you seeking the theoretical context might wish to consult A
Framework for Community Ecology (DOI: https://doi.org/10.1017/9781009067881)
recently completed with my co-author Daniel Laughlin.
My intention in preparing this book was to make a positive contribution to pro-
tecting and restoring wetlands. Thus, I have concluded each chapter with implica-
tions for (1) people who are managing protected wetlands or watersheds and (2)
people who are restoring wetlands. At the end of the book, I provide a further list of
review questions that should help with applying this book to both sets of
circumstances.
So, here is my concise introduction to wetland ecology based upon causal fac-
tors. It is arranged with the most important causal factors first, so even the first half
of the book will have a great deal of information that can be immediately applied to
conservation and restoration. May you protect and restore extensive areas of wet-
land during your lifetime.
Lanark County, ON, Canada Paul A. Keddy
Acknowledgments
I must begin by thanking Marleen Moore for first suggesting this project. I also
thank Li Zhang for offering me the opportunity to speak to her class in China which
challenged me to consider how best to simplify wetland ecology with a focus on
management. I’m particularly grateful to Cathy Keddy for her devoted assistance
during a protracted period of serious illness for both of us. She helped me at every
stage of the manuscript. Sadly, she herself did not live to see the book published, but
Cathy’s legacy is here on every page. I also appreciate my son, Ian Keddy, for being
there with software advice as needed. I’m also grateful to Max Finlayson for his
effort in reviewing the manuscript. Finally, I thank the many (patient) people who
have taught me these principles of wetland ecology, principles that I am now going
to share with you.
vii
Contents
1 Introduction to Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 What Is a Wetland? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Where Do Wetlands Occur? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 The Six Basic Types of Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Three Other Approaches to Wetland Classification . . . . . . . . . . . . . 7
1.4.1 A Global View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4.2 A Hydrogeomorphic View . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4.3 A View Based on Water Sources . . . . . . . . . . . . . . . . . . . . . 11
1.5 Ecoregions and Wetland Classification . . . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2 The Causal Factor Approach to Wetland Ecology . . . . . . . . . . . . . . . . 17
2.1 Causal Factors Are a Simplifying Tool for Wetland Ecology . . . . . 17
2.2 The Importance of Multiple Working Hypotheses . . . . . . . . . . . . . . 19
2.3 Revisiting Protection and Restoration . . . . . . . . . . . . . . . . . . . . . . . 22
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3 Duration of Flooding Is the Most Important Causal Factor . . . . . . . . 23
3.1 Flood Duration Controls Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2 Flooding Changes Wetland Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 Flooding Is a Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 How Plants Cope with Flooding . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.5 Flooding Has Secondary Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.1 Secondary Effects in Swamps . . . . . . . . . . . . . . . . . . . . . . . 28
3.5.2 Secondary Effects in Marshes . . . . . . . . . . . . . . . . . . . . . . . 29
3.5.3 Secondary Effects in Peatlands . . . . . . . . . . . . . . . . . . . . . . 30
3.5.4 Secondary Effects in Aquatic Wetlands . . . . . . . . . . . . . . . . 32
3.6 Flooding Is the Main Causal Factor . . . . . . . . . . . . . . . . . . . . . . . . . 32
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
ix
x Contents
4 Flood Pulses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.1 Changes in Water Level Are Natural in Lakes, Rivers,
and Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.2 Flood Pulses Are a Natural—And Necessary—Occurrence . . . . . . 40
4.3 Humans Are Interfering with Natural Flood Pulses . . . . . . . . . . . . . 42
4.4 Flood Pulses Increase Marsh Area and Diversity:
The Twin Limit Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.5 Flood Pulses Have Other Important Effects in Watersheds . . . . . . . 47
4.6 Vernal Pools: A Special Case of a General Principle . . . . . . . . . . . . 48
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5 Fertility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.1 Nitrogen and Phosphorus Control Fertility . . . . . . . . . . . . . . . . . . . 53
5.2 Peatlands Have Relatively Low Fertility . . . . . . . . . . . . . . . . . . . . . 57
5.3 The Everglades Have Extremely Low Fertility . . . . . . . . . . . . . . . . 57
5.4 Fertilization Threatens a Globally Imperiled Plant Species. . . . . . . 58
5.5 Increased Fertility Causes Many Other Changes in Wetlands . . . . . 60
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6 Natural Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.1 Natural Disturbances Remove Biomass . . . . . . . . . . . . . . . . . . . . . . 63
6.1.1 Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.1.2 Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.1.3 Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.1.4 Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.2 Fire Has Many Effects upon Wetlands . . . . . . . . . . . . . . . . . . . . . . . 65
6.3 Natural Disturbance Is Common along Rivers . . . . . . . . . . . . . . . . 66
6.4 Animals Create Natural Disturbance . . . . . . . . . . . . . . . . . . . . . . . . 68
6.5 Wetlands Recover from Disturbance by Seeds
and Rhizomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.6 Humans Have Big Effects When They Alter Natural
Disturbances in Landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7 Competition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.1 Competition Is a Biological Causal Factor . . . . . . . . . . . . . . . . . . . 73
7.2 Large Clonal Plants Tend to Exclude Weaker Competitors . . . . . . . 75
7.3 Competition Among Plants Drives Plant Succession . . . . . . . . . . . 76
7.4 Competition Among Plants Changes Animal Habitat . . . . . . . . . . . 78
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
8 Herbivory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
8.1 Herbivory Is a Biological Causal Factor . . . . . . . . . . . . . . . . . . . . . 81
8.2 Hippopotamus in Tropical Wetlands . . . . . . . . . . . . . . . . . . . . . . . . 82
8.3 Snow Geese in Northern Marshes . . . . . . . . . . . . . . . . . . . . . . . . . . 84
8.4 Selective Grazing Can Increase or Decrease Diversity . . . . . . . . . . 86