Plants that are common in the dune area between Egmond aan Zee and Bergen aan Zee are three thistle, bitterweed, bedstraw broomrape, common winglet, dune pansy, large thyme, vetch, common agrimony round evergreen and small beaver. Forest ranger Wouter Bol: “I am surprised that the species richness is so high. I knew that almost all species found were present in the researched area, but the density in which they were found is really unique!”
“In addition, a number of species emerged that I had not yet encountered myself, such as slender water rush, a species that can be found in wet dune slacks. I also noticed that there are still many growing areas of the nationally rare sand pansy, despite the fact that the plant, which is sensitive to foot traffic, occurs in places where many large grazers walk,” says forester Bol.
There are also populations of rare to very rare dune plants in the dune area
found, such as field gentian, parnassia, variegated horsetail, marsh helleborine, harlequin, bocce orchid, bee orchid, rosary (largest population in the Netherlands), small wintergreen, orange-yellow dandelion, dust seed, coltary stone thyme, grooved lamb’s lettuce and the special mosses bushy serpentine and rosette moss.
In 2022, the research agency van der Goes en Groot mapped the area between Bergen aan Zee and Egmond aan Zee on behalf of PWN. A mapping is an area-wide survey in which you make a complete inventory of a group of species (in this case plants) based on a pre-drawn list of species. This is an area of over 1,000 hectares, grazed mostly by Exmoor ponies and Highland cattle. The site is located in the transition area between lime-rich dune sand south of Egmond aan Zee and lime-poor sand north of Bergen aan Zee.
Special vegetation
The coastal strip is fairly dynamic here: there are dust spots everywhere. There is also one large drift, where sand is blown far into the area. The vegetation consists of marram grass with often sea buckthorn or creeping willow thickets on the leeward side. Behind this lie extensive dune grasslands, in which dune rose is the dominant species. In the south this is the calcareous variant of the grasslands, in the north the calcareous variant with many lichens. Due to the large and high dune ridges, many species-rich northern slopes can be found spread over this sub-area. Wet and humid dune valleys can be found in the lower parts, especially in the west behind the foredune.
Low shrubs of pedunculate oak increasingly increase eastward, eventually forming a broad zone of deciduous forest on the eastern border. There are also planted coniferous forests with black pine. Between the oak forests in the north are heaths with mainly heather. Around Egmond aan Zee lies the sea village landscape: a rich variety of fields, dune grasslands, holiday homes and paths provide very varied environmental conditions. Here you will find a very species-rich vegetation of mainly lime-loving species.
There are several reasons for species richness
In this area there are parts with calcareous and calcareous sand, which means that species that are bound to both soil types can occur here. In addition, there is relatively little forest in this dune area. This is partly because the family that managed the southern part of this area, known as the Wimmenummerduinen, used it as a hunting ground for a long period of time. As a result, little or no forest planting took place.
Another reason for the species richness is that two decades ago this part of the dunes was very grassy due to nitrogen deposition and the disappearance of rabbits. That is why area manager PWN has switched to grazing with exmoor ponies and Scottish Highlanders. The grazing pressure has been very high for a number of years, causing the dunes to become barren again. In addition, the animals kicked open the ground in many places. Partly due to the fact that there are very rich dunes in this area, dynamism returned to the landscape on a large scale. This means that there are many open spaces and the sand from these spaces is spread throughout the dune. This dynamic of blowouts and the formation of a notch in the strip of sand causes over-powdering of lime-rich and lime-poor sand (sand blown up by the wind). This benefits the special species of the dune.
Finally, the sea village landscape also has a positive effect on the species present. The mixing of light fertilization and the presence of calcareous sand has created a living environment that is very suitable for various dune species such as Silene Silene, Cone Silene, Ear Silene and Broomrape.
This is how a mapping survey works
Over a period of six years, PWN has its dune areas mapped for flora. This will be done in six rounds, because the site with more than 7500 hectares (15,000 football fields in size) is too large to investigate in one go. During the mapping, all growing places per quarter hectare of species that give an indication of the quality of the areas are noted, including species from the Red List, SNL-qualifying, N2000-typical and species characteristic of the dune area. The invasive exotics are also included. Each growing location is given a code and an estimate is made of how many plants of the relevant species are involved. PWN has the mapping carried out in the context of Natura 2000 and its own management evaluation. Comparable mapping is done in other dune areas through SNL subsidies. This makes the data comparable.
Comparison with other dune areas
The difference in species richness in the part of North Holland Dune Reserve mapped in 2022 compared to other dune areas can be clearly seen on the basis of the maps below. This shows the area north of Bergen aan Zee and the Kennemer dunes, south of the North Sea Canal. These areas also have relatively well-functioning dune ecosystems and are known to be rich in species. The maps show that the number of hectares where many qualifying and red list species occur on the Bergen-Egmond site is much higher than that of the other dune areas. A new category was even needed to reflect species richness (21-30 species).
Text: Wouter Bol, PWN & Bernard Oosterbaan, Van der Goes and Groot
Photo’s: PWN