The purpose of the 1997 Red List is partly to form a basis for work connected with maintaining the biodiversity in Denmark and partly to fulfil Danish obligations according to the Convention of Biodiversity.

The goals of the 1997 Red List are: to draw attention to species which have disappeared, are about to disappear or are rare to form the basis on which priorities in Danish nature monitoring should be made to form the basis for nature management and protection, nationally as well as internationally to fulfil the Danish obligations according to the Convention on Biodiversity by regularly publishing red lists of species in Denmark which have disappeared or are threatened The 1997 Red List deals with 19 groups of plants and animals. The overall number of species in these groups is ca 10,600 or about one third of all known species in Denmark. Of these 10,600 species, ca 4,000 are fungi or lichens, ca 1,050 are vascular plants, ca 5,300 are insects and 309 are vertebrates.

The 1997 Red List only includes plant and animal groups for which both present and former distributions in Denmark are sufficiently well known. These groups include fungi, lichens, vascular plants, mayflies, stoneflies, dragonflies, shield bugs, beetles, caddisflies, moths, burnet moths, butterflies, hoverflies, blackflies, fish, amphibians, reptiles, birds and mammals. The species in the 1997 Red List are classified as: "disappeared" (Ex), "critically endangered" (E), "vulnerable" (V) and "rare" (R). The category "disappeared" (former extinct) includes species of which self-reproductive populations were present after 1850, but which are now believed to have grown extinct in Denmark. The categories "critically endangered" and "vulnerable" include species which are threatened by extinction in the near future if the current negative trends continue. The category 'rare' includes species which are scarce in Denmark for natural causes.

In total, 3,142 species are included in the Danish 1997 Red List (table 1), of which 343 have disappeared, 1,608 are threatened ("critically endangered" or "vulnerable") and 1,191 are rare. It is only natural that 10-15 % of all species in a given area are rare. It should be mentioned that when summing up all species of a single category, the very large groups of often inconspicuous organisms seem unreasonable large (e.g. lichens, fungi and insects). Hence, the 19 groups of organisms should be considered independently. The Red List focuses - and must focus - exclusively on species which have disappeared, are threatened or rare, and not on species which currently are immigrating or generally increasing. Thus, the Danish 1997 Red List does not give a status of the general nature development in Denmark. A considerable number of plant and animal species have immigrated since 1850 and the majority of these are not included in the 1997 Red List. Concerning the status and development of Danish nature we refer to the NERI thematic report "Hvordan stĺr det til med naturen?" (Stoltze 1998b) which outlines tendencies in Danish nature based on 10 years of monitoring. Compared to the Danish 1990 Red List, the overall changes are insignificant and basically result from the inclusion of new groups of organisms and small changes in the criteria on which definitions are based. In the category "disappeared" the number of species has decreased since 1990. The many new records of species which in 1990 were listed as "disappeared" must be results of increased efforts to search for these particular species produced by the 1990 Red List. However, in many cases, the species have actually re-immigrated, e.g. white-tailed eagle, black stork and eagle owl. In total, 27 species have been found which were listed as "disappeared" in 1990, whereas 11 species have disappeared in the same period. The species which have disappeared include: Rhodocybe stangliana (fungus); Mertensia maritima, Genista germanica, Ranunculus nemorosus, Lycopodium alpinum and Orchis militaris (vascular plants); Lycaena tityrus and Coenonympha arcania (butterflies); Crex crex, Larus minutus and Acrocephalus arundinaceus (birds). Beside these 11 species, a large number of species of fungi, lichens and insects have not been observed after 1990, without being regarded as "disappeared". It should be emphasised that in a given area the species composition will always change from time to time due to the immigration, emigration or the growing extinct of individual species. During periods when habitats change, e.g. in connection with the change from glacial to interglacial periods or other changes in climate, the growing extinct and/or immigration of species may increase markedly and become larger than during any period since 1850. During the present stable climatic conditions in Denmark the natural disappearance and immigration of species probably is insignificant. Therefore it is considered likely that the current level of disappearance and immigration is human-induced. However, changes in species distribution occur which cannot be explained by our current knowledge. In the Danish 1997 Red List each group of organisms is treated in separate chapters. The 1997 Red List indicates a general positive trend for fresh water organisms (particularly mayflies, stoneflies, caddisflies and blackflies) and a general negative trend for butterflies. For the other groups of organisms no clear tendencies are detectable compared with the 1990 Red List. On species level notable positive trends include: increase in numbers for the orchids: Cypripedium calceolus, Anacamptis pyramidalis, Orchis ustulata (the latter is still critically endangered because it only survives in small numbers on a single locality) marked increase for the green tree frog Hyla arborea which no longer is included in the Danish Red List re-immigration of the large birds: white-tailed eagle Haliaeetus albicilla, black stork Ciconia nigra and eagle owl Bubo bubo clear signs of considerable increases in the Danish otter Lutra lutra population after an estimated minimum of 200 individuals In several cases, the positive tendencies are the results of effort to maintain the population levels of individual species (e.g. the green tree frog). On species level notable negative trends include: decrease in numbers for the orchids: Gymnadenia albida spp. albida and Gymnadenia conopsea the Astacus astacus (crayfish) is threatened by the crayfish disease which is spread by the introduced Pasifastacus leniusculus the birds white stork Ciconia ciconia and black grouse Tetrao tetrix are about to disappear despite great efforts to maintain them as part of the Danish fauna the crested lark Galerida cristata is rapidly decreasing and is now considered "critically endangered" the barred warbler Sylvia nisoria and hobby Falco subbuteo are continuously decreasing and are now considered "critically endangered" the garganey Anas querquedula, ruff Philomachus pugnax and oriole Oriolus oriolus are all decreasing and are now considered "vulnerable" In addition, all three forms of trout Salmo trutta occurring in Denmark, i.e. Salmo trutta f. fario, Salmo trutta f. lacustris and Salmo trutta f. trutta, have now been included in the Red List. The decline is caused by large-scale introduction of foreign trouts, even to watercourses where breeding conditions are not present. The remaining original and sustainable populations of trout occur on Bornholm and in a few other places in Denmark. These self-reproductive populations are stable and relatively well protected and therefore considered "rare". The habitats of the 1997 Red List species are presented in table 2.

More than half (54 %) of the redlisted species occur in forest. Next to forests grasslands have the highest proportions of the redlisted species (15 %) followed by waters and marshes with 12 and 10 % of the redlisted species respectively. An analysis has been carried out for vascular plants, butterflies and hoverflies which compares the number of species on the 1997 Red List in various categories with the total number of species in 11 habitats (see chapter 8.2). For these three groups of organisms the analysis showed that the pressure on open, natural habitats, each of which have a considerably lower number of species than forest, is greater than the immediate impression given by the summarised figures for groups on habitats (table 2). However, to evaluate the threats on each habitat, detailed analyses should be carried out for all groups of organisms.

The negative factors (called threats in the Danish 1990 Red List) affecting the species on the Red List are evaluated in the introduction to each group of organisms and discussed in general terms in Chapter 8.3. The impact of negative factors on individual species are poorly documented in general. On the other hand quite a lot of knowledge of the impact of negative factors on ecosystems are available. From this knowledge it is often possible to deduce or evaluate the impact of various factors on individual species. This deduced knowledge and qualified evaluation to a great extent form the basis for the evaluation of the status of each species. It is concluded that considerable research and monitoring is needed to achieve better knowledge about the factors which have an impact on the various species. Case studies on the species' ability to survive fragmentation into small and isolated populations is of particular interest to nature management. In addition, thorough studies on the impact of various farming methods on biodiversity are needed for most habitats. Even among groups of organisms treated in the 1997 Red List the knowledge of distribution and changes in populations are inadequate for a great number of species and even if the knowledge exists it is often hard to get at and very old. Thus, for most groups a clear need exists to strengthen monitoring and developing databases containing easily accessible information on the species included in the Danish Red List. Furthermore, it is concluded that five negative factors have been identified which affect most groups of organisms (in random order): eutrophication by direct outlets into nature and by the atmosphere overgrowing of extensively used habitats such as meadows, grasslands, heath land etc. eutrophication, drainage and subsequent overgrowing of open ponds and marshes drainage and intensive forestry isolation of populations In addition, disturbance is an important issue for birds and mammals, while releases of dense breeding populations of fish and ducks affect fresh water organisms.

Based on the Danish 1997 Red List it is assessed that long-term and appropriate maintaining of the biodiversity in Denmark may be achieved by (in random order): reducing eutrophication of natural ecosystems stop for fertilising meadows, grasslands and similar extensively used habitats adequate grazing of meadows, grasslands and similar extensively used habitats securing high water levels in pools and marshes and forests identifying and securing untouched or extensively managed woods restoring grasslands, heath land, meadows, pools, marshes, etc. taking appropriate action for single species, whenever needed.