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The state of our natural environment
New database of natural habitat types
The art of maintaining watercourses
Lake restoration
New knowledge on game wounding
Biodiversity in tropical rainforest
Zakenberg Ecological Research Operations (ZERO)
Greenland white-fronted geese travel far

Nature management

NERI’s work encompasses the problems associated with the use of our natural environment, including land use (agriculture, transport infrastruc-ture, etc.), fishing, tourism, hunting, and other outdoor recreational activities.

The state of our natural environment

Endeavours to protect and strengthen the natural environment and animals and plants are paying off. That is the conclusion of a new NERI report summarizing the results of a decade of monitoring nature.

The natural environment in Denmark has always been changing. In our day and age, it is mainly man’s use and consumption of nature that is the cause of the changes. Initiatives need therefore to be taken if the impoverishment of nature is to be avoided.

Efforts to protect and strengthen nature through legislation, nature management and nature restoration have yielded good results. The pyramidal orchid has once again established a vigorous population after having been close to extinction, a negative trend has been reversed for many clean-water insects, the otter and the tree frog are recovering, and even several large bird species have become reestablished, among others the white-tailed eagle. Common for each of these success stories is that the species in question was the subject of specific protection and rehabilitation efforts.

The new report – published in NERI’s Danish language popular science theme report series (TEMA-Rapport No. 22) – also stresses that the open types of natural ecosystem are in urgent need of attention if biodiversity is to be preserved. Commons are among the ecosystem types where the greatest percentage of species are threatened. While the Nature Protection Act provides possibilities to protect commons against cultivation and building, etc., there is no requirement to maintain grazing and reduce fertilization, these being prerequisites for the preservation of a large number of the characteristic species inhabiting our commons.

The number of species in the forests is large, and it is therefore natural that the forests also accommodate many of our threatened species. This was already clear from the previous Red Data Book of rare, vulnerable, endangered and extinct species from 1991. A subsequent revision of the Forestry Act in 1996 stipulated that the forests have to be managed in an environmentally sound manner. Moreover, the Natural Forests Strategy entails the establishment of a total of 50 km2 of natural forest in Denmark. Both initiatives should be of decisive positive significance for the threatened species in our forests.

A similar lesson can be drawn from the newly revised Red Data Book. The threat has worsened for those groups of species for which the basis for continued existence no longer exists. Butterflies are an example of a group of animals where the populations of several species are now so small and isolated that continued disappearance of species must be expected, irrespective of possible initiatives to reverse the trend.



Photo: CDanmark



Photo: CDanmark

Temarapport nr. 22/1998

NERI’s theme report on the state of Danish nature shows that the concerted efforts made in recent years to protect and strengthen nature are paying off. Populations of a number of animals and plants are improving. In other areas, things are not going so well. In particular, efforts are required to save the plants and animals inhabiting natural eco-system types in the open countryside such as commons, bogs, heaths and meadows.

In cooperation with the National Forest and Nature Agency, NERI now undertakes limited monitoring of our nature. At the international level, however, there is increasing pressure to expand monitoring of nature through the EU and international conventions. Hence there is good reason to believe that monitoring of nature will come to play an increasing role in NERI’s work in the future and thereby contribute to a wellneeded improvement of our understanding of the trends in nature.

New database of natural habitat types

Over the past 50 years, Danish botanists have drawn up thousands of lists of plants in various types of natural habitat. Despite this, no comprehensive description of Danish vegetation yet exists. NERI has therefore established a new database of information on the plant community at more than 9,000 test plots. The database can tell the type of plants that can grow in an area when one knows the habitat conditions. Conversely, it can also tell the type of habitat involved and the extent to which it is affected by man when one knows which plants grow there.

It is not easy to be nature in Denmark. But it is nearly just as difficult to be a botanist or a nature management official. The EU Habitat Directive, for example, requires the authorities to protect particular plant communities. But what plant communities are actually found in Denmark? Are there overlooked plant communities that in the long run eventually will need protection by the Habitat Directive?

In order to make life easier for nature management officials, NERI has now collated all available studies on vegetation and soil, hydrology, etc. in a major database in which the various types of habitat are classified. In a short time it will be made available for users - first and foremost the Counties, the National Forest and Nature Agency, and the research world. This is the first time in Denmark that all the information has been collated in one place in this way.

Models associated with the database make it easy to search in the comprehensive data material. If one types in data on the habitat conditions in an area, one can learn what should be able to grow there naturally. Among other things, this could be useful when considering nature restoration projects, etc. Conversely, when the botanist has investigated the plants in an area, the database will be able to tell what type of plant community the plant composition best resemble. Many habitat types are markedly affected by man. The database can tell which species are "missing" from the list of plants, and which species are "foreign" in relation to the natural plant community. This will make it easier for botanists and planners to obtain a general impression of the state of the area investigated.

The work on collating the information on Danish plant communities has revealed a considerable need to update the many 30-50 years old vegetation surveys. It has also become clear that there are large areas of Denmark for which no information is available.

In a short time, a test version of the database is to be tested by users. When testing is complete, the database will be made available via NERI’s Internet homepage.

Photo: Rasmus Ejrnæs, NERI



Photo: Rasmus Ejrnæs, NERI



Photo: Rasmus Ejrnæs, NERI



Photo: Rasmus Ejrnæs, NERI

NERI has now collated studies of Danish vegetation and habitat con-ditions in a database that provides the first comprehensive overview of Danish plant communities.

The art of maintaining watercourses

Some 15 years after the revised Watercourse Act entered into force, the Danish EPA has asked NERI to assess the effect of the changes in watercourse maintenance practice. Based on information from the Counties and Municipal-ities, NERI concludes that considerable changes have taken place in the direction of more gentle mainten-ance of the larger water-courses (county and municipal watercourses). However, the study also shows that clearance of aquatic weeds is now being undertaken more frequently than before.

When the Watercourse Act was revised in 1983, the purpose of the Act was extended from solely ensuring water drainage to also include consideration for the environ-ment. This opened up the possibility for more environmentally sound maintenance of the watercourses. Maintenance here means clearing the weeds from the water-course and along its banks, and dredging the bed free of sand and sediment.

The introduction of more gentle maintenance practice has meant that more weed is allowed to remain in the watercourse. The bed conditions in many watercourses have therefore been changed from uniform sandy reaches to more varied conditions with the presence of both gravel and stones. Moreover, as a result of the new maintenance practice the current channels have generally become narrower. In many places it is therefore necessary to revert to more hardhanded maintenance in order to meet with drainage requirements. There is consequently a need to revise watercourse maintenance guidelines if the environmental benefits already attained are to be preserved or enhanced.

NERI has investigated the significance of weed clearance practice in the river Gels in southern Jutland. The results show that regular weed clearance leads to changes in the species composition of the aquatic plant community, with rapidly growing species being favoured. In addition, there was a high density of sea trout in a reach where weed clearance had not been undertaken for 22 years, with no sea trout being found in two other reaches. From a few other studies it is known that the macroinvertebrates are also affected. In watercourses where drainage is unimportant, it can therefore be beneficial to cease weed clearance and sediment dredging completely. The setaside of riparian farmland and the reestablishment of riparian wetlands will typically entail a reduced need for drainage and will also reduce the transport of nutrients in watercourses.

During the course of the project it has become clear that documentation for the effects of the changes in watercourse maintenance practice is sparse. In future the effect of new measures directed at watercourses should therefore be documented more fully. NERI’s report on the effect of the changed watercourse maintenance practice is expected to be published in the spring.

In the coming years, NERI will continue the ongoing accumulation of knowledge in this area in connection with specific projects. In autumn 1999, NERI will hold a 2-day seminar for county and municipal authorities on present knowledge about the environmental effects of watercourse maintenance and restoration.



Photo: National Forest and Nature Agency, Bent Lauge Madsen


Photo: National Forest and Nature Agency, Bent Lauge Madsen

Photo: National Forest and Nature Agency, Bent Lauge Madsen

It is the river keepers who maintain the watercourses. In order to introduce more gentle maintenance practices, the Counties and the Freshwater Centre have run courses at which river keepers have learned how best to give due consideration to the environment when clearing weeds and dredging water-courses.

Lake restoration

The majority of Danish lakes continue to have turbid water and large numbers of phytoplankton. In many cases, however, the lake’s natural state can be re-established by some form of intervention. NERI has just completed a review of Danish experience with lake restoration.

The review shows that a number of conditions have to be met if lake restoration is to be successful. First and foremost, one has to clarify the reason for the lake’s turbid state. Is it due to excessive input of nutrients, or to the release of phosphorus accumulated in the sediment, or to a reduced population of zooplankton due to the presence of an excessive population of zooplanktivorous fish (roach and bream)?

The lake water phosphorus concentration is the decisive factor in determining what strategy to select since phosphorus is normally the key to limiting the growth of algae in lakes. Based on Danish experience, NERI recommends primarily undertaking restoration of lakes when the phosphorus concentration is below 50-100 microgrammes per litre, and even lower in the case of deep lakes (20-50 microgrammes per litre). Only then can one reasonably expect a permanent effect.

NERI has reviewed 20 practical examples of biological intervention. Danish experience mainly concerns reducing the lake stock of roach and bream in order to re-establish the zooplankton population so that it can control the phytoplankton. In order to achieve an effect, it is important to remove as great a percentage of these fish as possible: At least 70% have to be removed within a maximum of 1-2 years. The cost of reducing the fish stock in the examples reviewed lay in the range DKK 2–10,000 per hectare.

As an alternative or supplement to reducing the roach and bream populations one can stock the lake with piscivores in the form of young pike. Danish experience shows that it is necessary to release 1,000-1,500 young pike per hectare. NERI scientists have also experimented with the transplantation and protection of submerged macrophytes, among other places at lake Engelsholm.

Photo: Martin Søndergaard, NERI



Photo: J.A. Tvedebrink




Photo: CDanmark



Photo: CDanmark

In December 1998, NERI freshwater biologist Erik Jeppesen defended his DSc thesis entitled "The ecology of shallow lakes - Trophic interactions in the pelagial". Apart from working towards a basic understanding of lake ecology, Erik Jeppesen and his colleagues in Silkeborg are among the World's leaders in the field of lake restoration methods.

Physical-chemical intervention can sometimes be necessary, especially if large amounts of phosphorus have accumulated in the lake sediment and this internal phosphorus pool has a significant effect on the lake water phosphorus concentration. Intervention to reduce internal phosphorus loading is recommended if the summer phosphorus concentration is much higher than would otherwise be expected.

Only few physical-chemical methods have been tried in Denmark. By far the most expensive method is removal of the sediment. Largescale sediment removal has only been undertaken in lake Brabrand. A considerably cheaper method is oxygenation of the bottom water, with the price being in the same ranges or slightly more expensive than intervention in the fish stock. Oxygenation of the bottom water can only be used in stratified (deep) lakes, however.

In the long run it would be useful to return to the restored lakes to assess their longterm stability since the present conclusions are mainly based on relatively few years of postrestoration experience. It seems that it can take many years for the lakes to reach a new equilibrium.

The review of Danish experience with lake restoration has been published by the Danish EPA and is also the topic of a recent issue of NERI’s Danish language popular science theme report series (TEMA-Rapport No. 24). In the coming years, NERI will continue work on elucidating the mechanisms determining the shift between the clearwater and turbid states in lakes.

New knowledge on game wounding

New studies from NERI show that only few wounded pheasants are found after commercial hunting. On the other hand, NERI scientists have found shotgun pellets in one in five mallards. A practical study of eider duck hunting from motorboats showed that 85% of wounding can be avoided by simply adhering to good hunting practice.

Game wounding is the shadowy side of hunting. Considerable attention was aroused when a 1996 NERI theme report revealed that one wounded bird survives with pellets in its body for each bird bagged by hunters - at least in the case of hunting for eider duck and pinkfooted goose. The study led the Game Management Council to draw up an action plan to limit game wounding. An important element in the plan was a broad build-up of knowledge on the extent of game wounding in other game species and of the reasons for game wounding under the various forms of hunting. NERI evaluated the first results of these further studies in 1998.

Radiographic studies of pheasants revealed that very few birds had shotgun pellets in their bodies. It was therefore concluded that commercial pheasant hunting results in less game wounding than hunting for geese and eider ducks. This finding did not surprise the scientists because commercial pheasant hunting is a very well-organized form of hunting where the game is effectively retrieved using dogs.

NERI has also initiated studies of roe deer and foxes, but an insufficient number of animals have so far been investigated to enable any conclusions to be drawn. On the other hand, the preliminary results for the mallard indicate that game wounding could present a problem in this species. Out of 127 mallards X-rayed, 21% contained shotgun pellets in their bodies. New studies of the pink-footed goose showed that the percentage of both young and old geese containing shotgun pellets in their bodies was significantly lower than found in the earlier study. It is uncertain whether the fall is solely attributable to improved hunting practice, however. Hunting pressure on the species has fallen, which in itself will lead to fewer cases of game wounding.

Photo: J.L. Jeppesen, NERI

Photo:  C.R. Olesen, NERI

In cooperation with the National Forest and Nature Agency and the Danish Federation of Hunters, NERI has initiated a number of studies on the causes of game wounding under various forms of hunting. The results very much substantiate the assessment given in the 1996 theme report, namely that too long a firing range is the single most important reason for game wounding. This was clearly demonstrated in a study of so-called twilight hunting for mallard, a form of hunting practised until 11/2 hours after sunset. The results showed very clearly that the game wounding rate fell gradually as it became darker. The reason was that the firing range decreased from an average of 27-28 metres at sunset to 15 metres an hour later.

Another study has examined eider duck hunting from motorboats. To investigate how much game wounding can be reduced by following good hunting practice, only highly experienced hunters participated. The preliminary results suggest that if hunters were more conscientious about observing recommended firing ranges, game wounding could be reduced by 85%.

NERI’s status report will be utilized by the Game Management Council in its efforts to further reduce the incidence of game wounding. NERI will continue the investigations in the coming years.

NERI meets the hunters

Over the weekend 17-19 April 1998, NERI met with hunters at the exhibition "Hunting and Fishing 98" in Odense. NERI and the National Forest and Nature Agency shared a stand at which the main theme was game wounding. Over themes were modern satellite tracking methods for migratory birds, arable land as a habitat, the roe deer, set-aside fields, and pesticide-free border zones. Some 19,000 persons visited the exhibition. NERI's contribution attracted considerable attention and was well received.

Biodiversity in tropical rainforest

The rainforest is the essence of biological diversity. Although encompassing just 7% of the Earth’s surface, rainforests boast around half of all the World’s animal and plant species. In areas with high human population density, however, the rainforests are threatened by man who clears the forest to procure timber or land for grazing. NERI is heading a Danish-Latin American project that is helping strengthen the basis for sustainable management of the mountain rainforests along the Andes.

Biological diversity in the Andes area is already partly protected in national parks and reserves. The protected areas are not always located where there is most need for them, however, but are sited in thinly populated areas based on the desire to avoid conflicts. Conversely, the areas in which people decide to settle often contain many rare species or have a high biological diversity. In practice, the species most in need of protection are often the ones that are least protected. The results of the studies indicate that the following measures can help improve the situation:

The project will be brought to an end in 1999. The results have been made available to the local authorities - as well as to Danish authorities involved in aid projects in tropical rainforest, primarily in South America, but also in Southeast Asia. Finally, the results are summarized in a recently published issue of NERI’s popular science theme report series (TEMA-Rapport No. 25).

Zackenberg Ecological Research Operations (ZERO)

Fluctuations in nature have to be followed for many years before it is possible to determine whether changes are anthropogenic. The Arctic is probably the part of the World where least is known about natural fluctuations. At the same time, it is the area most sensitive to pressures such as global warming. From 1998, NERI has therefore taken over responsibility for the biological monitoring programme at Zackenberg field station in northeast Greenland.

The field station at Zackenberg was established by the Danish Polar Centre in 1995 to create facilities for a longterm interdisciplinary research. The Zackenberg valley distinguishes itself by having an unusually broad range of habitat types and lying close to the boundary between the relatively mild and fertile southern part of northeast Greenland and the more barren High Arctic region. One can therefore expect to see particularly clear reactions to changes in for example snow cover, summer precipitation, solar radiation and temperature.

NERI’s biological monitoring in the area, which is financed by the Arctic Environment Programme under the Danish Environment and Catastrophe Support Scheme, follows a broad range of organisms, the focus of attention being on the occurrence and distribution of plant communities, arthropods, birds, lemmings and musk ox. There are also monitoring programmes for climate and geographic processes run by the Greenland Survey and the University of Copenhagen, respectively. All the monitoring programmes are longterm.

Zackenberg also serves as the base for research projects aimed at elucidating the function and dynamics of Arctic ecosystems. NERI has hitherto been involved in two research projects at Zackenberg, a study of nutrient and organic matter turn-over in Young Sund and a survey of the lakes in the area.

In the coming years, NERI will continue work on the two research projects. The objective is detailed elucidation of Arctic marine and freshwater ecosystems and their sensitivity to climate changes. Further information on the activities at Zackenberg can be found on the Danish Polar Center’s Internet homepage: www.dpc.dk






Photo: Hans Meltofte, NERI




Photo: Hans Meltofte, NERI

The field station at Zackenberg serves as the base for research and monitoring activities that can help demonstrate the effects of global changes in the environment and climate, both natural and anthropogenic.

Greenland white-fronted geese travel far

NERI has shown that the Greenland white-fronted goose has important staging areas in western Greenland. The geese stage there for 10 days during the spring migration, eating around the clock before flying on to the breeding grounds. In order to safeguard the populations it is therefore important to protect the geese against disturbances from mineral exploration and tourism during that period.

The Greenland white-fronted goose is doing well. The population is increasing after hunting restrictions have been imposed while it overwinters in Ireland and Scotland. Nevertheless, the population totals only 30,000 birds and therefore needs protection.

In order to protect the goose all year round it is necessary to know its fly way and in particular the staging areas where it refuels during the spring migration. This last refuelling is of vital significance for its breeding success. The attachment of satellite transmitters to the back of the geese is a particularly useful method of studying their movement since the transmitter informs the biologists how long the geese remain at the staging areas.

The results confirm that the Greenland white-fronted goose uses staging areas in both Iceland and western Greenland during the spring migration. The total fly way is 3,000 km, and underway the geese reach speeds of up to 100 km per hour. The stopover in western Greenland is important because the geese eat around the clock while they are there. They stay in snowfree marsh areas in the central part of western Greenland, particularly feeding on the nutritious lower parts of cotton grass stems.

The staging areas lie in an area where exploration for minerals is growing rapidly. NERI has therefore recommended to the Bureau of Minerals and Petroleum, Greenland that helicopter flights and other activities causing disturbance should be restricted in the vicinity of the newly discovered staging areas when the Greenland whitefronted goose stages there, i.e. 1-20 May.

Photo: Christian Glahder, NERI

Greenland white-fronted goose with satellite transmitter attached to its back. The small transmitter was glued in place and secured with an elastic harness.

NERI’s studies showed that the geese stay in their breeding grounds for approx. 4 months before starting their autumn migration in mid September. Upon their return to Ireland the geese had lost the satellite transmitters, which by then had fulfilled their purpose. The geese still had their neck rings, though, and these could be read with the aid of a telescope. None of the geese brought young with them on their return.

NERI biologists will mark yet another group of geese in 1999 so as to gain further knowledge of the staging areas in western Greenland, which are spread along a 500 km stretch from Nuuk in the south to Ilulissat in the north.

Migratory path of 4 Greenland white-fronted geese indicating the staging areas and breeding grounds. By attaching satellite transmitters to the back of the geese, NERI scientists have confirmed that this relatively small goose population has important staging areas in western Greenland.

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