ELSEVIER Ecological Engineering 7 (1996) 251 253

ECOLOGICAL ENGINEERING

Guest Editorial

Ecological engineering and nature conservation

Jos T.A. Verhoeven

This special issue contains papers presented at the workshop 'Ecological Engineering for Ecosystem Restoration' held in Zeist, The Netherlands in November 1994, sponsored by the Contec (the Swiss division of the EU-Comett programme), the International Ecological Engineering Society and the University of Utrecht. This workshop focused primarily on the use of Ecological Engineering approaches to restore or mitigate the floristic or faunistic diversity in deteriorated (semi-)natural areas, or to create nature areas in previously agricultural fields or grasslands. It hosted 41 participants from the Netherlands and the neighboring countries Belgium, Denmark, Germany, Great Britain and Switzerland.

The seven papers in this issue together give a good representation of the topics discussed during the meeting. The discussions clarified the differences between nature restoration and management according to Ecological Engineering principles and the more traditional methods of nature management. Particularly in Western Europe, traditional nature management requires regular, rather drastic human interventions which work against the natural processes of succession or hydrology. Examples are the annual mowing of vegetation, the continuous pumping necessary to maintain water levels or to supply water with a certain quality. Although these measures will still be necessary to conserve some of our botanical richness, they are often the perpetuation of former agricultural practices; it is at least a challenge to try to manage nature reserves in a much less drastic way by creating a set of environmental conditions and 'let nature go', i.e., let the vegetation and fauna sort itself out. Examples of such attempts have been described in the papers by Schrautzer et al., and by Jansen and Roelofs for mesotrophic grasslands.

During the discussions, concern was expressed that this can only work if all potentially suitable species are there or are able to reach the site by dispersal. In cases where nature areas are being developed in formerly agricultural areas, it may be necessary to distribute seeds of a whole range of species in order to enable a development in the desired direction. This is still a controversial topic: most nature conservation agencies act very cautiously and limit seed dispersal to accidental trans- ports between nature reserves through hay left on mowing machines transported from

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252 J.T.A. Verhoet'en / Ecolo,~ical En~,ineerin~, 7 ( 1996~ 251 --253

one reserve to the next. It was emphasized during the workshop that caution is needed in the sense that seeds should always be collected in nearby locations through mowing ol' the whole vegetation; the hay could then be distributed on the newly set-aside area.

Another issue is the conservation of herbaceous plant communities. Natural succes- sion leads to forest in almost all terrestrial habitats in our climate. Examples of more natural ways to conserve a differentiated landscape with open areas as well as forests are the use of large herbivores and the set-back of succession to the very initial stages. Such an approach requires much larger areas, in which all successional stages occur in different sections, which rotate through the area. An example of this is described in the paper by Beltman et al. which deals with the conservation of fen landscapes in the Vechtplassen area. Here, alder forests in turf ponds have been cut and the peat has been dredged, thus restoring the initial stage of the terrestrialization sere. Rather than the annual mowing, once every 100 years dredging of the end stage should create a landscape with all the herbaceous fen stages, provided that the water chemistry is appropriate.

Another topic discussed was the mitigation of damage done to natural values by large construction works associated with infrastructure. This special issue contains two examples of approaches to minimize or mitigate such damage. The paper by Liebrand and Sykora deals with measures designed to restore species-rich river dike vegetation after the reconstruction and enlargement of the dikes. The measures included the use of the original turf removed from the old dike, and the use of seed mixtures. Here, again, the presence of seeds or vegetative diaspores is crucial for a rapid vegetation develop- ment. The paper by Cuperus et al. describes the effectiveness of a whole suite of measures to mitigate the effects of the construction of a large 4-lane motorway. The measures were primarily designed to mitigate the isolating effects of the road on animal populations and consisted of fauna tunnels and overpasses.

Two more general papers complete this special issue. Van Ierland and De Man give an overview of the economic aspects of Ecological Engineering. They discuss the potential uses and values of natural ecosystems, based on their biodiversity and their functioning. Only if society becomes fully aware of these benefits, sufficient pressure will be put on their conservation, rehabilitation or restoration. In Europe, with its small proportion of the area protected as nature reserves, nature restoration and even nature reconstruction on grounds in prolonged use for agriculture is necessary to prevent the loss of biodiversity. Another very important draw-back for the European natural values are the current agricultural practices, many of which are non-sustainable. Jorgensen and Nielsen reviewed the principles of Ecological Engineering for application to agriculture. They show that also in agriculture it is necessary to work with nature's forces and to respect ecological principles, such as the cycling of nutrients and the controls on population dynamics of pest species.

The restoration and development of nature in previously disturbed areas requires a good knowledge basis on natural processes, a well-specified target and some basic agreement among ecologists, nature managers and engineers on the best methods and

J.T.A. Verhoeven / Ecological Engineering 7 (1996) 251-253 253

procedures to reach that target. It is my hope that this special issue may contribute to

these deve lopments .

Jos T.A. Verhoeven

Depar tment of Plant Eco logy and Evolu t ionary Bio logy

Utrecht Univers i ty

P.O. Box 800.84

NL-3508 TB Utrecht

The Nether lands

Acknowledgements

I am especial ly indebted to Johannes Heeb from Wolhusen , Switzer land, who

initiated the Zeist workshop and has successful ly appl ied for support f rom the Swiss

divis ion of EU-Comet t .

References

Beltman, B., van den Brock, T., van Maanen, K. and Vaneveld, K., 1996. Measures to develop a rich-fen landscape with a full range of successional stages. Ecol. Eng.. 7: 299-313.

Cuperus, R., Kanters, K.J. and Piepers, A.A.G., 1996. Ecological compensation of the impacts of a road. Preliminary compensation for the A50 road link (Eindhoven-Oss, The Netherlands). Ecol. Eng.. 7: 327-349.

Jansen, A.J.M. and Roelofs, J.G.M., 1996. Restoration of Cirsio-Molinietum wet meadows by sod cutting. Ecol. Eng., 7: 279-298.

JOrgensen, S.E. and Nielsen, S.N., 1996. Application of ecological engineering principles in agriculture. Ecol. Eng., 7: 373-381.

Liebrand, C. and Sykora, K.V., 1996. Restoration of semi-natural, species-rich grasslands on river dikes after reconstruction. Ecol. Eng., 7: 315-326.

Schrautzer, J., Asshoff, M. and Miilller, F., 1996. Restoration strategies lbr wet grasslands in Northern Germany. Ecol. Eng., 7: 255-278.

van Ierland, E.C. and de Man, N., 1996. Ecological Engineering: first steps towards economic analysis. Ecol. Eng., 7: 351-371.