Putting wetland science to practice: a review

Book review: 
Causal factors for Wetland Management and Restoration: A Concise Guide 
Author: Paul A. Keddy
eBook ISBN 978-3-031-21788-3
Published: 11 March 2023
Pages: XIII, 158 pp.
Publisher: Springer Cham.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) In these unprecedented times, we find ourselves amidst the sixth mass extinction while simultaneously embarking on the United Nations Decade on Ecosystem Restoration, spanning from 2021 to 2030. As if the stakes were not high enough, this timeframe serves as the ultimate countdown for achieving the Sustainable Development Goals (SDGs), vociferously advocated by scientists as the last window of opportunity to prevent the catastrophic climate change. Amidst this critical juncture, no other ecosystem plays a more pivotal role in achieving SDGs and buffering our civilization against climate change as wetlands. With their ability to regulate floods, purify and store water, produce oxygen, sequester carbon, provide food and showcase unrivalled biodiversity, wetlands stand as the veritable champions of our planet. It is in this regard that Dr. Paul Keddy's 'Causal factors for Wetland Management and Restoration: A Concise Guide' could not be more timely. Through this insightful book, he seeks to equip park managers, landscape architects, consultants, planners and engineers with a succinct and invaluable resource that will enable them to make tangible differences in the conservation and revitalization of wetlands.
General public and policy makers, mostly, assume that wetlands are just waterbodies due to a weak understanding of what wetlands truly are. Dr Keddy, at the onset, irons out this deficit and provides a solid ecological foundation by defining what a wetland is. It is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic processes, which, in turn, forces the biota, particularly rooted plants, to adapt to flooding." Inundation is the predominant feature that characterizes wetlands. These could be seasonally inundated with an ephemeral presence of water for half the year and look like grasslands during the other half. Flooding cuts off aerial oxygen supply to the soil. Wetland life forms must thus adapt to survive both inundation and low oxygen levels. Such wetlands can be categorized into six major types: swamp, marsh,

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bog, fen, wet meadow and aquatic -each experiencing different intensities and duration of inundation.
The second chapter of the book is what might be Dr. Keddy's notable and a seminal contribution to the budding field of wetland ecology-'the causal factor approach'. This approach revolves around identifying and understanding the environmental factors that govern the very essence of wetlands-their composition and functionality. Therefore, this chapter provides a key to a small set of essential tools, offering a simplified lens to comprehend the complexities of wetland ecosystems. In areas where wetlands remain relatively unscathed, managers can focus on preserving the existing state by safeguarding the causal factors at play. In other areas, where wetlands have suffered damage, tweaking these causal factors will be paramount in the pursuit of restoring them to their desired state. The trifecta of flooding, nutrients and natural disturbances (through biomass removal) emerge as the pivotal forces, wielding significant influence over the rich tapestry of wetland variation.
Within the realm of the 'causal factor approach', duration of flooding is the most important factor creating a variety of wetland types along a spectrum of varying water depths -from permanently flooded to temporarily flooded. The link between ecological concepts and their application in conservation is also swiftly described. For instance, it has been advised that while creating new wetlands, a variety of water depths and gentle slopes should be incorporated into the design that will then sustain a matrix of different wetland vegetation types and provide a sanctuary to a plethora of life forms. Such concepts are especially important to perceive wetlands as ecosystems that are implicitly tied to the fate of rivers. Even subtle fluctuation in water depths created by the varying duration of floods holds the power to metamorphose a wetland from a marsh to a swamp, orchestrating a shift from a plant community dominated by tree-less, herbaceous forms to a reign of woody plants. This understanding provides the basis for realizing the effect of dams and river diversion projects on the persistence of wetlands. A single glance at the easily graspable conceptual diagrams that characterize the book helps us to answer questions and anticipate the far-reaching consequences of policies that continue to change the wet landscapes.
The latter portion of the book delves into a myriad of other factors that mould the character of wetlands, including the intriguing dynamics of plant competition, the impact of herbivory, the transformative effects of burial or sedimentation, the influence of salinity, the ramification of roads, the challenges posed by invasive species, and the crucial interplay with human population size. Throughout these chapters, the author skillfully provides tailored guidelines for wetland managers with different objectives -whether their aim is to maintain the existing state of wetlands or to embark on the ambitious journey of restoring them to a desired condition.
As we approach the book's culmination, the concluding chapters weave together a comprehensive synthesis of concepts, shedding light on the interconnectedness of individual wetlands within a vast global network. We come to understand that each wetland, be it nestled within a protected area, situated along a buffer zone, or forming part of a landscapespanning corridor, contributes to a greater whole, a magnificent continuum that extends far beyond the boundaries of any single site. The last chapter serves as an invaluable exercise for wetland managers, presenting a thought-provoking series of questions that once answered by invoking the general principles introduced in the beginning, will pave the way towards achieving practical objectives in the protection and restoration of local wetlands.
Most river basins of Asia are severely degraded and fragmented because of river diversion projects. Based on the principles elucidated in the book, it might be worthwhile to predict how the dynamics of wetlands and wetland complexes strung together to the fate of the rivers might be affected due to decreasing water flow and increasing sedimentation. This will set the stage to examine corresponding impact on the ecological community and society. For instance, what happens when an aquatic wetland progresses towards a marsh and a marsh towards a swamp? Understanding the nature and pace of such a change will enable us to perceive the effect of this change on both biodiversity and dependent human communities (especially fishing communities) as well as the consequence for larger societies. This might then expedite restoration efforts if the change and/or degradation of wetland ecological functions has alarming consequences for biodiversity and society.

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