Water for aquatic nature

The map shows the nature value of wet and humid ecosystems in the Netherlands. The map is based on observed plant species (per km²) from the Floron Foundation database (FLORBASE-2N), combined with a nature value calculation with the model DEMNAT (Deltares) based on the degree of development. Areas with high natural value depend on the availability of good quality water to allow for the development of rare species. This map is thus an indication of areas where good quality water is available for aquatic and terrestrial nature. In the Netherlands, roughly five types of nature can be distinguished: 1. High sandy soils with forests and dry heath 2. Wet nature with high water levels such as the IJsselmeer, the weather ribs and surface water-fed peat lakes. 3. Tormented nature that is often found in brook valleys. 4. Flooding nature, such as the floodplains in the river area. 5. Dunes and beaches Aquatic nature is in Type 2 and 3. Salt-dependent nature is bound to high groundwater levels and groundwater with a specific chemical composition (bass rich and not contaminated). The tormented nature reserves are mainly found in stream valleys, but also in other areas where there is a torment situation, such as along the Hondsrug, the Utrechtse Heuvelrug and the Veluwe where nature is influenced by groundwater. Other systems that are highly dependent on the groundwater situation are high bogs and fens. Also in dune areas, nature is often dependent on specific influence by groundwater. In much tormented nature there is dehydration and acidification due to low groundwater levels in surrounding areas (through drainage) or by groundwater abstractions (Aggenbach, 2005, Witte et al. 2007). Also, in aquatic ecosystems, dehydration can occur when too much water drains away, to surrounding drained area with lower water levels. To compensate for this, foreign water is allowed in, which often does not have the desired quality. Both aquatic and terrestrial ecosystems often involve fertilisation due to food-rich groundwater or surface water. All these bottlenecks lead to a decline in biodiversity (Aggenbach, 2005, Witte et al. 2007). Multiple ecosystem services use the same water supply. For aquatic nature (rivers, streams, ditches and creeks) it is important that there is sufficient water of good quality. Available groundwater resources play a crucial role in this, not only for the supply of sufficient water, but also of the right quality. The capacity of these stocks decreases through use for other ecosystem services, such as abstractions for irrigation and drinking water (Figure 1). Other developments that interfere with groundwater levels and altitudes, such as (increase) drainage in agricultural areas, can also have a significant restrictive effect on torment-dependent nature.