Wetland Restoration, Flood Pulsing, and Disturbance Dynamics

Wetland Restoration: Flood Pulsing and Disturbance Dynamics has a magazine-like personality, with attention-getting headlines and ample illustrations. Among its many positive features are the bibliography with more than 1,000 entries and the two appendices, which provide well-referenced data on hundreds of wetland plants. The first appendix gives seed dispersal modes for each plant listed, the other seed germination requirements. In addition, there is a guide to wetland web sites around the world. Together with the glossary and the index, these sections occupy about one-third of the book’s 388 pages. This book has a mission--to inform with efficiency. The body of Wetland Restoration is filled with tables, subject boxes and figures, giving the entire volume an information-dense quality. The narrative comprises a minor fraction of the book, mainly serving to introduce readers to a topic. Numerous graphs and models are reprinted from the literature, and the author provides many photos from wetlands around the world (unfortunately, most are poorly reproduced). Readers of this book, whom I assume will be advanced university students, professional wetland restoration consultants, and fellow scientists, should be familiar with Middleton’s terse writing style. Nonetheless, confusing definitions in the glossary and various errors in the text (e.g., "hand sewn seeds") are somewhat distracting. Overall, it would be difficult for individuals new to ecology or restoration to follow the arguments and examples. There are six chapters: 1. Disturbance dynamics in wetlands, 2. Restoration theory, 3. From seed to adult: Missing links in restoration (a title whose meaning evades me), 4. Restoration and disturbance dynamics in restored landscapes, 5. Revegetation alternatives, and 6. Case histories. True to the subtitle, Middleton emphasizes the importance of flood pulsing from the first line of chapter 1, "Wetlands are besieged by disturbances from which they recover over time." She illustrates flood pulses in riverine wetlands, cypress swamps and monsoonal wetlands, calling for more attention to the dynamics of wetland hydrology in restoration ("These ideas are completely ignored in the regulatory process." [p. 11]). She describes how dams, channelization, levees, and water diversions alter river flows and gives examples of how large woody debris, beaver, herbivores, fire, and other human and natural disturbances affect various wetland systems. Exactly how to use this knowledge in wetland restoration is less clear, as the book does not collect the various recommendations into a comprehensive set of guidelines. Following the introduction of flood pulsing and disturbance dynamics, the author shifts her attention to succession theory, which she presents as central to restoration ("Succession and restoration are largely the same phenomenon." [p. 70]). Middleton presents a dichotomy in which Gleasonian successional theory is equated with self-design in restoration projects, while Clementsian succession is equated with designer approaches. The glossary is of little help here; it defines Gleasonian succession as "in wetlands, cyclic wetland dynamics in which ’once a wetland, always a wetland.’ Change is brought about by the maturation and fluctuation of species in response to disturbance and environmental change" and Clementsian succession as "synonymous with the terms classical succession, relay floristics, and facilitation." What comprised a lengthy debate in the early ecological literature is not easily reduced to an argument, as presented by Middleton, with frequent reference to the writings of Arnold van der Valk, over whether or not to replant a wetland restoration site. The question for restorationists is not "Should we design plantings or allow vegetation to disperse on its own?" but "When and for which species are plantings needed?" Some sites and some species may need to be planted to achieve certain goals, while other situations may revegetate satisfactorily via dispersal. For example, in southern California salt marshes, Salicornia virginica is so widespread and such an aggressive invader that planting it is rarely necessary; in fact, introducing it to a site early on may hinder the establishment of other desired species. Several halophytes native to the region are poorly dispersed and slow to establish even when planted. Costeffective restoration projects thus rely on both natural dispersal and strategic planting, i.e., both self-design and designer approaches. By establishing two "schools of thought," Middleton does more to perpetuate than settle any lingering debate about how succession operates. In one text box, she asks why Clementsian succession is still included in high school textbooks--another place where the historical debate cannot be treated adequately and, in condensed form, is easy to criticize. Her discussion of historical succession theory stereotypes both Clements and Gleason and does little to resolve restoration planting issues. Middleton’s other discussions of ecological theory involve more useful ideas. For example, she indicates that flood pulses create opportunities for seedling establishment and that island biogeography theory might help predict invasion of restoration sites (sites closer to a source of propagules will more likely be colonized without assistance). Still, the treatment of theory is not well developed. For example, the concept of a "safe site" is introduced as a theory but the creation of safe sites is not discussed as a tool that can help restorationists improve revegetation efforts. The river continuum concept is discussed in three short paragraphs, without indicating how it can be used to plan restoration projects. Likewise, fire is presented as necessary in wetland restoration, but