Grenspark De Zoom-Kalmthoutse Heide

Grenspark De Zoom-Kalmthoutse Heide is a unique cross-border national park straddling the border between the Netherlands (North Brabant) and Belgium (Antwerp province), covering approximately 2,000 hectares. The Dutch portion is known as De Zoom and the Belgian part as Kalmthoutse Heide; together they form one of the most significant heathland landscapes in the Low Countries. The park was established as a pioneering cross-border protected area in 1990, one of the first bilateral parks in Western Europe. The landscape is characterised by dry and wet heathland, drift sand, pine woodland, and peat bogs traversed by the Belgian-Dutch border.

The park supports breeding populations of European nightjar, woodlark, and European stonechat across its heathland. The wet heath and bog areas are important for Eurasian curlew, which has become rare across the region. Adder and sand lizard are present on the drier sandy sections. Natterjack toad (Epidalea calamita) breeds in the seasonal pools on the sandy heaths. Smooth snake (Coronella austriaca) has been recorded in the park. The park serves as a key stepping stone in the cross-border ecological network connecting the Belgian Campine region to the Dutch Brabant heaths. Roe deer are common throughout, and the occasional wildcat visit has been recorded in the Belgian sector.

Dry heathland dominated by heather (Calluna vulgaris) and bell heather (Erica cinerea) covers the majority of the park. Cross-leaved heath (Erica tetralix) and Sphagnum mosses characterise wet heath areas, with common cotton grass (Eriophorum angustifolium) in the wettest zones. The drift sand areas support pioneer vegetation of sand couch, sand sedge, and lichens. Invasive American black cherry (Prunus serotina) is the primary management challenge and has spread extensively across parts of the park. The Belgian sector contains some of the best examples of humid, species-rich heathland in the Campine region.

The park lies on the Campine Plateau, a low-lying sandy terrace underlain by Pliocene and Pleistocene coversands deposited by the Rhine-Meuse river system. The terrain is almost entirely flat, with only slight undulations created by drift sand movement. Peat has accumulated in wet depressions to depths of up to 2 metres in places. The drift sand areas represent destabilised aeolian sand that has moved episodically since the medieval period. The border between the Netherlands and Belgium runs through the park and is marked by old boundary stones from the 1830s Belgian independence settlement.

The park has a temperate maritime climate similar to other Low Country heathlands. Winters are mild and wet; January averages 2–3°C. Summers are warm with July averages around 17–18°C. Annual precipitation is approximately 750–800 mm. The flat, open heathland experiences strong south-westerly winds that drive sand transport. Drought stress on heathland vegetation is increasing with climate warming. The park is at moderate risk from heathland fires during dry summers, and several significant fires have occurred in recent decades. Cross-border coordination of fire response between Dutch and Belgian emergency services has been formalised.

The heathland on both sides of the border was used as communal grazing land for centuries. During the Belgian revolution of 1830, the border was drawn through the middle of what was previously a single contiguous heathland area managed by local communities. The border location contributed to the area's historical use by smugglers moving goods between the two countries. During World War II, Belgian resistance fighters used the cross-border nature of the area to move people and goods. The boundary stones that mark the frontier are still visible on some of the park's walking trails.

De Zoom was protected as a nature reserve in the Netherlands from the 1970s and the Kalmthoutse Heide was similarly protected in Belgium. The formal cross-border park was established in 1990 through an agreement between the Dutch and Belgian governments, creating a joint management structure—a first of its kind in Europe. A joint management committee meets regularly to coordinate conservation planning, invasive species control, fire management, and visitor programmes. The park has been extended on the Belgian side and serves as a model for transboundary conservation across Europe.

The park has an extensive trail network crossing the border freely; no passport or documentation is required to hike between countries. Walking routes of 5 to 18 kilometres traverse the heathland, drift sand, and pine forest. A border trail specifically follows the historic boundary markers. Cycling routes connect the park to Roosendaal (Netherlands) and Kalmthout (Belgium). The Kalmthout Arboretum, adjacent to the park, contains an internationally renowned collection of rare trees and shrubs. Bird watching is popular year-round, with nightjar listening walks in June and July a seasonal highlight.

The Dutch visitor centre is located near Hoogerheide, providing information on the park and the cross-border area. The Belgian Kalmthout visitor centre is near the Kalmthout village entrance. Car parking is available at multiple access points on both sides of the border. The Dutch section is accessible by bus from Bergen op Zoom; the Belgian section is accessible from Antwerp by train to Kalmthout station. Cycling from Roosendaal and Bergen op Zoom to the park takes 20–30 minutes. The park is open year-round with no entrance fee.

The main conservation priority is heathland restoration through control of American black cherry (Prunus serotina), which has colonised substantial areas on the sandy soils. Joint cross-border management plans address sod-cutting, controlled burning, and grazing with sheep and cattle. A major joint restoration project funded by EU LIFE Nature grants has been running since the 2000s. Fire risk management is coordinated across the border, with joint fire brigade exercises. Both sides monitor adder, nightjar, and sand lizard as key indicator species. Cross-border hydrological restoration projects have raised water tables in the wet heath zones.