Wetlands

by

Paul A. Keddy

• LAST REVIEWED: 25 February 2016
• LAST MODIFIED: 25 February 2016
• DOI: 10.1093/obo/9780199363445-0051

Introduction

Wetlands have always influenced humans. Early civilizations first arose along the edges of rivers in the fertile soils of floodplains. Wetlands also produce many benefits for humans—along with fertile soils for agriculture, they provide food such as fish and water birds, and, of course, freshwater. Additionally, wetlands have other vital roles that are less obvious. They produce oxygen, store carbon, and process nitrogen. Since wetlands form at the interface of terrestrial and aquatic ecosystems, they possess features of both. They are often overlooked in standard books, since terrestrial ecologists focus on drier habitats, while limnologists focus on deep water. Shallow water, and seasonally flooded areas, fall comfortably into neither category. All wetlands share one causal factor: flooding. While wetlands may be highly variable in appearance and species composition, flooding produces distinctive soil processes and adaptations of the biota. Thus wetlands and water are inseparable. This treatment will first introduce you to some basic overviews that explain what a wetland is, what different kinds of wetlands exist, and some key processes that occur within them (General Guides and Introductions). Then we will turn to causal factors: flooding creates wetlands, so it receives a full section. Then we will consider how nutrient availability modifies wetlands. Other Casual Factors, such as salinity, competition, herbivory, and roads, are combined into a third section. Having provided this foundation, we will look at the global distributions (Geography of Wetlands). By this point, you will know what a wetland is, where they occur, and the main factors that affect their abundance and composition. We will then explore two more specialized topics. First, monographs are identified that apply to particular regions of the Earth (Regional Monographs). Second, we look at aquatic plants; they are a relatively small group with important implications for the understanding of wetlands as a whole (Aquatic Plants). We close with a section on conservation of wetlands. Two general obstacles must be met in coming to grips with the scientific literature in this field. First, much of the work on wetlands is scattered across ecological journals and may not even appear under key word searches for wetland; instead, material may appear under a term such as bog, fen, shoreline, lake, floodplain, pothole, playa, peatland, or mire (or a dozen other terms). Second, this discipline seems to have attracted a large number of conference symposia, the findings of which are recorded often in expensive books with a haphazard collection of papers, written by a haphazard collection of people, with no unifying theme whatsoever except that all deal with wet areas. Hence, the need is pressing for a few general principles to structure one’s knowledge. Here we focus on general causal factors and their relative importance.

General Guides and Introductions

To learn about wetlands and communicate with other human beings, we need a common frame of reference. Otherwise, our knowledge is more like a heap of bricks than a properly constructed building. Let us begin with three books that provide this common frame of reference. First, Dugan 2005 is a guide that is accessible to the general reader and useful for the professional. The author begins with two basic topics: What are wetlands and why we need wetlands. He then continues with a two-hundred-page survey of the world’s wetlands, supplemented with maps and beautiful illustrations. Next, Wetland Ecology: Principles and Conservation (Keddy 2010) also begins with a general introduction to wetlands. It then proceeds through a series of causal factors that make wetlands, roughly in the order of their importance: flooding, fertility, disturbance, competition, herbivory, and burial. Each of these chapters begins with general principles and then explores experimental and descriptive work that shows how these principles apply to wetlands around the world. Third, Wetlands (Mitsch and Gosselink 2015) also begins with a general introduction to wetlands. However, unlike Dugan 2005 and Keddy 2010, it then divides coverage into five types of wetland ecosystem, with separate chapters on tidal marshes, mangrove swamps, freshwater marshes, freshwater swamps, and peatlands. Whereas Dugan and Keddy emphasize biological diversity, Mitsch and Gosselink tend to emphasize energy flow and biogeochemistry. If you read these three books, you can consider yourself well informed on wetlands as a whole. You can think of these as the trunk upon which many more branches of knowledge are organized. The interested reader can then proceed in two directions. In the first case, one can deepen one’s knowledge of the causal factors that create wetlands and proceed with topics such as Flooding and Flood Pulses and Nutrients. Or one can focus on the many kinds of wetlands that arise in a local context and proceed with Regional Monographs. Finally, with the above sources as a foundation, one can directly consult specialized journals, such as Wetlands, the journal published by the Society of Wetland Scientists since 1981. Otherwise, much of the specialist work on wetland ecology is scattered across journals that deal with ecology and geography. Further, owing to the commercial importance of animals in wetlands (think ducks, muskrats, fish) many papers can be found in fish and wildlife journals, work that is too often marred by an inordinate emphasis upon production of one or a few species of animals. Many wetlands have been damaged in the name of “wildlife management.”

• Dugan, Patrick, ed. 2005. Guide to wetlands. Richmond Hill, ON: Firefly.

  An illustrated guide to the ecology and conservation of the world’s wetlands. Lucid, comprehensive, beautifully illustrated, and affordable. A starting point for everyone who wishes to explore the topic of wetlands further.

• Keddy, Paul A. 2010. Wetland ecology: Principles and conservation. 2d ed. Cambridge, UK: Cambridge Univ. Press.

  DOI: 10.1017/CBO9780511778179

  The causal factors that create wetlands. Focuses more on wetlands as a whole rather than breaking them into five types. Also an emphasis upon natural habitats and biodiversity conservation in a global context.

• Mitsch, William J., and James G. Gosselink. 2015. Wetlands. 5th ed. Hoboken, NJ: Wiley.

  A popular book in the United States where there is a complicated regulatory framework for wetland management. Focuses more on energy flow and nutrient cycling and, as the table of contents denotes, traditional wetland management.

• Wetlands. 1981–.

  An international journal covering wetland biology, ecology, hydrology, soils, biogeochemistry, management, laws and regulations. Published by Springer on behalf of the Society of Wetland Scientists. Since 2005 a sister publication has been published called Wetland Science and Practice.