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English Summary

The entire documentation of the development of Denmark's open natural and semi-natural habitats and their species is sporadic. Nevertheless, the studies available clearly depict a vulnerable nature under heavy stress. The trends particularly affecting the development of these habitat types will be described in the following sections. Some of these development trends are mutually enforced.

1. The debt from the past
During the last 200 years all open natural and semi-natural habitats have been reduced to a fraction of their previous range. Many Danish flora and fauna species are associated with the open natural habitat types and a great part of these species are nowadays red-listed. Even if the number of habitats is stabilised, a further reduction of a wide range of red-listed species is to be expected, as there may be a considerable time delay between the damage of habitats and the consequential extinction of populations. Many species can survive for quite some time in non-sustainable habitats where the final local extinction will only occur at a later stage - typically caused by coinciding instances of natural and manmade fluctuations. Despite the enhanced protection of the remaining nature, the decline has continued for the last 20 years and a further decline in Denmark's biological diversity must be expected before this development is reversed.

2. Progress of the few - at the cost of the many
At present, the open natural and semi-natural habitats are reasonably safeguarded at area level (quantitatively). The core of the present problems and preservation is the quality of the remaining habitats. Thus, the quality is today threatened by eutrophication. Eutrophication favours the few species adapted to nutrientrich habitats at the cost of the many hardy plants and specialist animals that are adapted to oligotrophic open habitats. The nutrients are retained by the soil and hence the eutrophication is at many locations practically irreversible unless drastic action is taken.

3. The open nature becomes overgrown
The open natural and seminatural habitats are threatened by scrub encroachment caused for instance by cessation of grazing and mowing, eutrophication, and lowering of the water table. Reduction of the natural dynamics is also contributing to scrub encroachment. The effects of eutrophication, drainage and ceased dynamics are that habitats, which used to change very slowly after discontinuation of extensive farming practices, are today changing dramatically within only a few years.

4. Nature needs space - and time
Plants and animals living in small habitats are particularly liable to disappear. Small areas are also exposed to an increased impact from the surroundings. In small isolated nature areas it is also difficult to implement nature management methods providing for natural dynamic processes such as erosion, littoral sand drift, water level fluctuations, and the species' need for continuity. Even in large nature areas dynamic nature management proves difficult and in Denmark there are only few large nature areas where nature is not directly or indirectly affected by dune stabilisation, coastal protection, watercourse regulation, drainage or damming.

5. Global changes
Our atmosphere and climate are undergoing changes resulting in rise of temperature and increased water levels in the seas. The impact on nature is unknown but near-shore natural habitat types such as dunes and salt meadows are, of course, especially endangered. Rapid climatic changes will in particular affect those species that have a low dispersal rate and are associated with the most fragmented natural habitat types, thus being unable 'travel' to new habitats.

6. Lack of knowledge
Although the development trends in the terrestrial natural habitat types are well documented, the conclusion is that due to lack of terrestrial research and monitoring we cannot quantify the observed decline and are unable to predict the magnitude of the efforts needed to reverse the development.



Full report in pdf. format (596 KB)
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Helle Thomsen

01.11.2007


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