Kortenhoeff wetter and richer in species: forester Imke van Gisbergen talks about it

Grenspark Kalmthoutse Heide is surprisingly versatile: from drifting dunes to forests, heathland and fens. In the small nature reserve Kortenhoeff of about a hundred hectares, you come across all these biotopes. The area lies in the Grenspark, between Hoogerheide and Huijbergen, and is managed by Staatsbosbeheer. Forester Public Imke van Gisbergen talks about the nature restoration that was recently completed.

What do you think makes Kortenhoeff such a special area?

"For me, Kortenhoeff is really a little pearl on the Brabantse Wal. The area is small-scale, but incredibly rich in variety: wet and dry heathland, shifting dunes, two weakly buffered fens and an acidic fens. Because of this mix of biotopes, many unusual species can be found here. The area also has an interesting history. During World War II, for instance, a fake landing strip with wooden planes was located here as a diversion for Woensdrecht airbase. Later, an attempt was made to start an orchard; the old fruit shed is still a nice remnant of this. It makes Kortenhoeff a place where nature and history coincide."

You have been working hard on nature restoration at the Forestry Commission recently. What exactly did you do?

"In the past few months, we have been working on humidifying the area. In short, we want to retain water longer instead of draining it quickly. This may sound crazy when you consider that visitors in the winter of 2024 were going through the area on wellies, but if you think of a couple of freakishly dry summers, it becomes clear why this is necessary. The dry spells are falling earlier and earlier in the year and that affects species that depend on fens."

Why was humidification necessary?

"If the water level drops too early and for too long, species that are so characteristic of this area disappear. Ponds may periodically run dry in summer, but too early and too long is very bad for larvae of dragonflies and amphibians. They cannot survive a dry spring, for instance. Even flora such as the bone broom, a rare lily-like plant that likes to grow on acidic and moist soil, is in danger of disappearing if drought persists. And when fens run dry, the whole system changes: plants die, nutrients are released and young trees establish themselves in the fens soil. For the fen whitethroat dragonfly, for example, this is disastrous."

How did you do that?

"We have deepened or filled in ditches in several places. These are mainly ditches that drain water from the area, which is exactly what we want to prevent. Special sand was brought in that meets strict requirements for use in nature reserves and matches the soil already present in the area. At the same time, we have raised paths so that visitors can continue to experience the area. It is important that people also see and feel why this nature is worthwhile."

What does this mean for nature in Kortenhoeff?

"By retaining relatively nutrient-poor water longer, we can better regulate the water level and improve the internal water balance. This directly helps preserve nature target types such as wet heath and fens. Ultimately, it's about preserving, restoring and promoting the species that belong to this landscape."

Which species benefit?

"Because the area is so diverse, many species benefit from humidification. Take for instance the fen whitethroat dragonfly. This is a beautiful dragonfly species that is listed as vulnerable on the Red List and is clearly declining in numbers. It lives in the riparian zone of fens, which are fed by rainwater and are therefore very sensitive to fluctuations in the water level. During a dry spring or summer, these places fall dry and the larvae do not survive that period. Water retention allows these fens to stay wet longer, giving the dragonflies a chance.

But other species also benefit: among dragonflies, the dragonfly glazier, among birds the little grebe, among amphibians the crested newt and moor frog, and among reptiles the viviparous lizard. Among the butterflies, the butterfly species include the heath blue, the greenshank and the spotted tadpole. And among the plants several bog mosses, but the bone break really stands out. When you see those little yellow flowers in June, you know the water balance is doing well."

And now that the work is finished: what do you expect for the future?

"We can now maintain the water level better, making the system more robust for dry summers. Ultimately, this will result in richer biodiversity, with species that belong here and that make Kortenhoeff so special. For me, it is extra nice that visitors can continue to experience this area. When people soon see dragonflies flying above the fens or the bone broom in bloom, you know: this is what we do it for."

Discover it yourself

"Visitors may still experience a slight inconvenience because the applied sand on some paths is still a bit loose. This needs some time to harden, so it will be easier to walk in the future. Just a matter of patience," says Imke.

Walkers can discover the area via walking route Mouse (1.8 km) and walking route Owl (3 km). Both routes can be accessed via the digital experience map of the Grenspark: