The landscape's unique 'petgaten' (peat holes) were created by 18th-century peat harvesting, where turf was cut and spread on narrow balks to dry.
The reserve is an official Natura 2000 site, designated for its high ecological value as a fenland ecosystem.
It is home to the rare large copper butterfly, which depends on specific water dock plants found in the marshland.
The hydrology of the site is carefully managed to prevent the peat from drying out and releasing carbon.
The area functions as a biological corridor connecting various wetland habitats across Friesland.
De Deelen is a protected peatland nature reserve located near Heerenveen, characterized by shallow pools, quaking bogs, and extensive reed beds. The landscape was formed by centuries of peat extraction, creating a distinctive pattern of elongated ponds separated by narrow strips of land. It serves as a vital habitat for rare flora and fauna, including the marsh harrier and various dragonfly species. The area is managed by It Fryske Gea, which maintains walking routes and boardwalks throughout the reserve. It is a critical region for breeding birds that rely on the mosaic of water and wetland vegetation. The geography includes both open water areas and dense, swampy thickets that are difficult to access without prepared trails.
From the elevated wooden viewpoints overlooking the open water of the peat holes during golden hour.
Wear waterproof, sturdy footwear, as the paths can become muddy and uneven after rainfall.
Bring binoculars for birdwatching, particularly to spot marsh harriers and bearded reedlings.
Stick to marked trails, as the terrain off-path consists of fragile and potentially unstable bog soil.
Attempting to walk off the maintained paths, which risks damaging the fragile peat structure and potentially sinking into soft mud.
Keep dogs on a leash to protect ground-nesting birds; do not pick plants or disturb wildlife.
