De Levende Natuur nummer 3 van 2005 (English summary)

A century Naardermeer and its breeding birds

Wijs, W.J.R. de

Naardermeer is a natural lake and marsh area. It survived several attempts to make it a polder in previous centuries and survived an attempt to be turned into a rubbish tip. The latter provoked action of naturalists, resulting in the founding of Vereniging Natuurmonumenten in 1905. From then on natural succession in the area turned some reedbeds into woodland, but there is still 150 ha (23%) of reedland present. The most important breeding birds are colonial species such as Spoonbill, Purple heron, Cormorant and Black tern, but also Great reed warbler, Savi’s warbler and several other rare marshland species. The colonial species, which suffered strong prosecution in earlier centuries, found a safe haven here, although populations showed strong ups and downs. The Spoonbill abandoned the area after severe disturbance by foxes in 1988. Reedland warblers have been counted as early as 1943, enabling a comparison with later years. Savi’s warbler and Sedge warbler have increased since then, Great reed warbler has decreased. The other species show less obvious trends. Recently the large population increase of Greyleg geese has resulted in poor reedbed quality and quantity. This caused a population decrease in Reed warbler and changes in distribution of Reed warbler and Great reed warbler. Several measures have been taken to ensure this nature reserve can maintain or improve its natural values. Water is managed thoroughly, both in quality and in quantity. It is believed this will ensure its existance for the next century.

Changes in the management of the forests of Natuurmonumenten

Frentz, W.I. & H.N. Siebel

Natuurmonumenten manages forests for almost a century. The first deecades the management aimed mainly at timber production. The money was needed for the purchase and management of the nature reserves. Apart from that, knowledge was lacking about management which tries to increase the values for plants and animals. This changes after heavy storms in 1972 and 1973. The fallen trees were used by biologists to discuss changes in the management of the forests. Since then the management of Natuurmonumenten has been aimed at the realisation of more natural forests, a.o. by creating open gaps in the forest. It is assumed that also in the long run in many forests an active management will be needed to ensure a high biodiversity since natural processes are not strong enough.

Heathland management by Natuurmonumenten

Dirks, P.H.A.M. & N. van der Ploeg

The amount of heathland in The Netherlands has strongly decreased from about 400.000 ha in 1900 till 36.000 ha nowadays. Natuurmonumenten owns and manages about 6000 hectares. During the last 15 years these 6000 ha has been intensively managed. Most common management regimes were mowing, removing of the topsoil and grazing by cattle. Over 5000 ha is currently grazed. Due to the management the cover of grasses has been reduced, but still several plant species are diminishing in number due to acidification and desiccation. This is especially the case for species characteristic for growing in weakly buffered habitats. Several bird species (Black grouse, Great grey shrike) are diminishing in number as a result of the decrease in the area of heathland. However, it is the loss of variation in structure that is the main cause of the decrease in numbers of many species of evertebrates. During the last years management has already become more small scaled, but further improvement is necessary. For the future of the Dutch heathland and its characteristic species it is necessary to reduce the problems of separation of small heathlands, acidification, eutrophication en desiccation. Assistance of the government is needed to solve these problems.

Dutch fen areas: decrease or increase?

Piek, H. & A. Boosten

Between 1998 and 2003 Natuurmonumenten carried out an extensive bog restoration project in the Fochteloërveen. Already in 1985 dams had been constructed in the strongly desiccated and grass (Molinia) covered Fochteloërveen in order to improve the conservation of the rainwater surplus. In spite of the encouraging results, considerable parts became too wet or remained too dry for bog restoration. By constructing wooden sheet piles the size of the earlier compartments is reduced and their number increased. As a result the (ground) water levels increased and its fluctuations have reduced over an area of about a 1000 ha, creating favourable conditions for growth of peat mosses. Despite the high nitrogen deposition and the unnatural drainage the first results for vegetation development are encouraging (Altenburg et al., this issue).After many years of decline for characteristic bird species, for example Tetrao tetrix, Limosa limosa and Numenius arquata now a change seems to take place. Most striking is the establishment of the Grus grus, which seems to profit from the large, undisturbed open space, the rewetting and the presence of extensively managed agriculture fields surrounding the bog. This border area also plays an important role as a foraging (particularly geese and birds of prey) and breeding area for other bird species. The number of water - and marsh birds such as Luscinia svecica, Porzana porzana, Tachybaptus ruficollis en Botaurus stellaris increased as a direct result of the rewetting.Some characteristic bog species such as Saxicola rubetra, Saxicola torquata, Coronella austriaca, Rana arvalis en Coenonympha tullia remained stable or showed a significant increase. By building tunnels under and fences alongside roads the number of traffic victims under reptilians, amphibians, mammals and birds strongly decreased.

Bog vegetations in Fochteloërveen

Altenburg, W., M. Groeneweg & K. van der Veen

Fochteloërveen (1500 ha) is a remnant of a once 10,000 hectares large raised bog area in the northern part of The Netherlands. The typical bog vegetation is currently heavily degraded, caused by agricultural use in the 19th century (buckwheat cultivation), lowering of the groundwater level and increased atmospheric deposition in the 20th century. The owner of Fochteloërveen, Natuurmonumenten, has taken measures by building a number of dams in the bog in 1984/85 and 1999-2001, in order to raise the average water levels and to restore part of the bog vegetation.As a result of these measures, Fochteloërveen has became much wetter. The ubiquitous Molinia caerulea has shown a strong decline, while especially Sphagnum cuspidatum, Eriophorum angustifolium and Eriophorum vaginatum show a strong increase. Also the characteristic bog species Sphagnum papillosum, S. magellanicum and Andromeda polifolia show a profound increase.The present-day conditions of Fochteloërveen are not those of a healthy sphagnum bog; especially the high levels of atmosferic nitrogen deposition is a point of concern. Nevertheless the first results of the restoration efforts indicate that well planned hydrological measures can lead to a swift increase of typical bog species in Dutch bogs. The coming years will show if an ongoing increase of these species is possible in Fochteloërveen, despite the relatively high atmosferic deposition.

100 years searching for balans between nature recreation and nature conservation

From the beginning of Natuurmonumenten people started visiting nature areas. First there was just a small elite group. In the 1950’s more people of the workingclass became able to enjoy nature. It started to get busy in some nature areas. And as a result also the concerns about damage to nature started. On Texel for example the manager decided to close ‘De Zandkuil’, an insect reserve, because walkers damaged the vulnerable insectworld in their sandholes. In the 1990’s the rangers started looking for more possibilities for nature recreation, under the pressure of more and more visitors. Zoning the areas is a way to keep some areas quiet for nature and let people enjoy other parts which are less vulnerable. The concern for the future is ‘where does it stop, how much more visitors can nature handle?’. We want to show people the wonders of nature, so they will understand and help to protect, but we also want to protect nature for the animals and the plants. Isn’t that why Thijsse set up Natuurmonumenten in the first place?

The interest of Natuurmonumenten in the beauty of the landscape

Lochem-van der Wel, S. van & M. Purmer

In the past 100 years, landscape became an important issue in the work of Natuurmonumenten. Attention shifted in the society as well as for Natuurmonumenten from a more ethical point of view, ‘the beauty of the landscape’, to the appreciation of the historical landscape. Nowadays Natuurmonumenten stresses the unity of nature and historical values in the man made Dutch landscape. For the future the organisation hopes that new interest in the beauty of the landscape can help to preserve it for the next generations.

100 years of wildlife management by Natuurmonumenten

Broek, T.G.Y. van den

From the beginning Natuurmonumenten was very critical to hunting and the law on hunting. In the early years, hunting in the organisation’s nature reserves was allowed, because the rent could be used in managing existing reserves and purchasing new ones. In the seventies, however, increasing opposition among its members to hunting made Natuurmonumenten change its hunting policy from ‘yes, provided that’ to ‘no, unless’ in 1979. At this moment, 87% of the total land area owned by Natuurmonumenten is free of hunting agreements.

Small fauna and the development of species management

Broek, T.G.Y. van den & T. de Groot

This paper describes the increase in attention paid to the small fauna in nature conservation. At the end of the seventies, volunteers became more interested in identifying and mapping these groups. Important tools were newly published field guides and an affordable fieldworkers atlas and digital distribution files. Due to this increase in knowledge of species distribution, ecology and endangerment, conservationists developed a better idea of which species are important to their management goals. Examples of small-scale management measures employed by Natuurmonumenten are given for some (groups of) species. In the future these species action plans will be united into area action plans.

30 years of grazing by Natuurmonumenten

Piek, H.

In this article the author shows the effects of grazing in different nature areas managed by Natuurmonumenten. There are differences between horse grazing and by cattle, yearround and just in summer, in the dunes or woods. The positive experiences of the last thirty years stimulate Natuurmonumenten to continue this way of management.

100 year documents about the nature in the reserves of Natuurmonumenten

Aanholt, M.R.C.G. van den & W.M. de Bie

The library of the 'Vereniging Natuurmonumenten' has a collection containing over 26.000 titles of publications, mainly dealing with research about the reserves of the Association. Research material dating from the period before 1945 is few but is of special importance because of its unicity. From 1945 a scientific approach of nature preservation starts. So from 1945 onwards all kinds of inventory research is available. Initially this mainly consists of flora- and (breeding) bird data. From the seventies onwards the collection enlarges steadily and the planned way of working more and more influences the research. The focus of inventory and research enlarges gradually, including more animal groups. From the eighties onwards also research about topics such as recreation, hydrology and cultural history enter the collection.

100 years of changes in nature management

Piek, H. & B.F. van Tooren

The development of nature management in the nature reserves of Vereniging Natuurmonumenten is described. During the first 50 years continuation of the former (agricultural) use was dominant within the reserves. The last 50 years a more scientific base of nature management developed, strongly stimulated by the search for solutions for problems like acification, eutrophication and lowered water tables. For the next 100 years the authors expect that apart from spatial planning which was a major issue also during the past century, biodiversity from an international point of view (Habitat and Bird Directives) and climatological changes will strongly affect nature management.