HYDROLOGICAL SYSTEMS BEYOND A NATURE-RESERVE, THE MAJOR PROBLEM IN WETLAND CONSERVATION OF NAARDERMEER (THE NETHERLANDS)

Ecological relations within a wetland depend on it is hydrology, but this is determined largely by what happens outside the wetland area. These statements are illustrated with respect to the Naardermeer nature reserve in the Netherlands. Succession and eutrophication have led to a reduction in the variety of vegetation types in the area. Eutrophication has been caused by a lowering of the water levels, deposition of guano in bird colonies, pollution of surface water and groundwater, and atmospheric deposition. The fact that most restoration activities have to be executed outside the wetland demonstrates that the management of the conservation of wetland ecosystems needs to operate on a regional scale. The conservation of a wetland depends on water bevels. However, the qualitative aspects of hydrology are also important. Since landscape ecological relations with the surrounding area provide for transport of nutrients, a wetland is not isolated. Changes in hydrology have an impact on processes that affect the ecosystems in different ways. These relations ave illustrated from a reserve in the centre of the Netherlands.