Wetlands – Your Comments / SILnews 23

Wetlands – Your Comments / SILnews 23

My question in SILNEWS 22, "Wetlands - where are the limnologists?" provoked an interesting and very varied response from several members. All agreed that too few aquatic scientists are working on the numerous wetland projects in progress around the world. The reasons suggested ranged from deliberate exclusion by project co-ordinators wanting rapid, overview analyses, to insufficient emphasis on interactions between ecosystems in the education of limnologists. I was sent several examples of limnologists actively involved in wetland research.

Stephen Hamilton (hamilton@kbs.msu.edu) has been working with S.J. Sippel and John Melack on wetland limnology in the Pantanal of Brazil (e.g. Oxygen depletion and carbon dioxide and methane production in water of the Pantanal wetland of Brazil. Biogeochemistry 30:115-141, 1995.) and with W.M. Lewis and S.J. Sippel on the Orinoco River floodplain (Energy sources for aquatic animals in the Orinoco River floodplain: evidence from stable isotopes, Oecologia 89: 324-330, 1992). He pointed out that, although the study of tropical wetlands is mostly still in the descriptive phase and only a handful of researchers are covering vast areas, in the US they are much further on in understanding wetland ecosystems. He recommended a book summarising the recent work of a committee formed by the US National Research Council, chaired by W.M. Lewis Jr., entitled "Wetlands: Characteristics and Boundaries" (ISBN 0-309-05134-7; 1995. National Academy Press, Washington, D.C. and Oxford [nap@opp.i-way.co.uk]).

Kevin Murphy, Caroline Allan, Jeremy Hills, Vicky Abernethy and Nigel Willby of Glasgow University in Scotland (k.murphy@bio.gla.ac.uk) worked on the plant ecology of the wetlands (including wetland water bodies) included in the FAEWE project that I described in SILNEWS 22 but only some of the results have as yet been published (e.g. Evidence for consistent functional groups of wetland vegetation across a broad geo- graphical range of Europe, Wetland Ecology & Management 4:51-63, 1996; A method for classifying European riverine wetland ecosystems using functional vegetation groups, Functional Ecology 8, 242-252). More recently Kevin Murphy has been working in collaboration with Brazilian researchers Sidinei Thomaz (University of Maringa), Mauricio Bini (University of Goiania) and Antonio Camargo (Universidade Estadual Paulista) on aquatic macrophytes of the channels and associated waterbodies occupying the floodplain wetlands of the Rio Parana in southern Brazil. This area is threatened by a major hydro-electric scheme. Similar schemes elsewhere on the Rio Parana (for example the very large Itaipu Reservoir scheme) have led to major limnological problems, such as the development of mass aquatic weed growths. Funding is currently being sought from the EU to extend this work.

Richard Robarts (robartsr@nhrisv.nhrc.sk.ec.gc.ca) is leading a team at the National Hydrology Research Institute in Saskatoon, Canada, working on wetlands and lakes on the prairies. They focus on the effects of agricultural practices, land uses, climate change and increased ultraviolet radiation on wetland nutrient cycling, biological diversity and productivity, food chain dynamics, and hydrological processes. His biggest problem is getting funds because there is no specific funding program for prairie wetland research in Canada. This probably also applies to other wetland types but peatland researchers get money from several sources, including the peat industry. Richard's experience apparently also suggests that most limnologists face a whole new way of thinking if suddenly asked to turn their attention to wetlands. A limnologist accustomed to deep open water, for example, and a Clarke-Bumpus, or Friedinger sampler on 100 m of rope, is initially challenged by many wetland systems - the water may be only knee deep, and there are all these plants in the way! A bit of a culture shock - so most limnologists stick to what they know. The need for open mindedness in this respect, and on a wider front, is confirmed by the experience of Teresa Vegas outlined below.

Eville Gorham (University of Minnesota) feels that the education of limnologists is at least partly to blame. He responded to my comment by telling me that the US National Research Council has recently published "Freshwater Ecosystems; revitalizing educational programs in Limnology" (ISBN 0-309-05443-5; 1996. 384 pp. National Academy Press, see above) which deals, among others, with the question that I raised. Professor Gorham contributed two background papers to the discussions preceding preparation of this volume ("Wetlands: an essential component of curricula in limnology" and "Linkages among diverse aquatic ecosystems: a neglected field of study") and if the ideas therein are taken up by teachers they may help to reduce the culture shock. His thesis is that traditional courses teach students about lakes and rivers as if they were separate ecosystems and too little emphasis is placed on the interactions even between parts of the overall aquatic system, let alone interactions between aquatic and terrestrial systems.

Maybe this explains why landscape ecologists, with their increasingly sophisticated software and analytical techniques are tending to dominate wetland studies. Perhaps what is needed is not only more inter-ecosystem interaction in education but also more inter- disciplinary interaction between limnologists and other specialists.

Richard added to the above: "There is no real appreciation by students or the general public about the role and value of wetlands in the ecology of large regions of the world. Pond is a word often used for a wetland and it has connotations of being pretty, maybe not quite part of the real world - possibly a holdover from childhood stories of frogs and princesses! Even in the vast area of the Canadian prairies most people living here do not appreciate the value of wetlands. Yet when driving through the prairies most people remark on at least two things: how much sky there is and the beautiful wetlands with their birds and waterfowl - oases in a big sky desert!"

Just as I was finalising the above piece I received the following. My thanks to all contributors to this discussion. Mary J. Burgis

At the water's edge - the limnologists become confused

(Response to the comment "At the Water's Edge - where are the limnologists?", by M. Burgis, SILNEWS 22, 31 March 1997)

Are wetlands terrestrial or are they aquatic? I would answer: both. And this could be the reason why Limnologists, at least in South America , seem to evade their thorough study.

Traditionally, limnology has evolved as the ecology of lakes and later of rivers. Lakes and rivers are conspicuous in the sense that lakes have been viewed as depressions with vertically organized structural dynamics, and rivers as a convergent system of channels with a well defined horizontal direction of flow confined within a channel. Wetlands challenge this orthodox limnological approach: although by definition lakes and rivers are considered wetland systems (IUCN), it seems to me that wetlands refer rather to more unconfined situations where the interaction between water and land creates very tight relationships of ecological interdependence, i.e., they are semi-aquatic systems.

In such systems water accumulates from a few centimeters to about one meter or more above the ground and stays there seasonally or permanently, and their lack of perceptible boundaries is one very important characteristic of wetlands. This makes much more difficult the understanding of the driving hydrological patterns, which are determinants with regard to residence time, throughflow and mass-level of nutrients, and the interconnection of different kinds of wetlands.

In trying to determine the spatial and temporal extent of the water layer, two new issues emerge: the relevance of geomorphology and of the groundwater table. Geomorphological features, especially in flat lands, can be very subtle, but important, determinants of water circulation / accumulation patterns. High groundwater levels are common in wetland systems, providing an additional water supply that helps perpetuate flood conditions.

Finally, the wide variety of biotic communities comprising wetland systems are worth mentioning. In tropical environments, wetland communities comprise not only aquatic organisms living in water-bodies such as oxbow and floodplain lakes, but also other types such as floating and swampy grasslands, swamp forests of different kinds, estuarine and coastal mangroves and palm communities, among others. All of them depend more or less on flooded conditions and many species show particular adaptations to them.

My current area of study is the Orinoco Delta, a giant wetland. According to my own experience, it is beyond the possibility of common limnologists, like myself, to undertake the study of such environments without the support of other professionals. I would say that some of the challenges limnologists have to face when making research on wetlands are:

  • Definition of boundaries that help delimit the study area; this must be necessarily be undertaken using aerial photographs and satellite images.
  • Understanding the highly complex hydrological patterns for which the participation of wetland hydrologists is necessary.
  • Neither aquatic nor terrestrial elements can be isolated for study, because in most cases they are interdependent and need to be considered together; thus the study of the biotic, biogeochemical and biophysical components must be carried out by different specialists.

This awareness necessarily leads to the conclusion that research on wetlands should integrate and harmonize different methodologies, expertise, points of view and even expectations of the components of multidisciplinary teams. Therefore, limnological projects need to be carried out within the framework of this holistic approach.

Dr. Teresa Vegas, GEOHIDRA C.A., Dep. of Ecology and Environmental Quality Caracas, Venezuela epxg134_at_mrv-op-cc-2-ep13@email.maraven.pdv.com