Dünnwalder Wald

The Prussian original survey of 1844 still shows wide stretches of open heath here. By the time of the Prussian resurvey of 1893, large parts had already been planted in regimented rows with Scots pine, a tree not native to the Lower Rhine Bay. Farming and military use kept pockets of open, species-rich habitat intact until the second wave of afforestation after the war, for example in the Dellbrücker Heide nature reserve and around the Schlebusch dunes. Building development, afforestation, gravel extraction and later recultivation destroyed almost all of these areas as well by the 1980s at the latest.

In 1956, Cologne's city administration and the Schutzgemeinschaft Deutscher Wald (German Forest Protection Association) launched an afforestation programme for the right-bank part of the city to shield residential areas from exhaust fumes and dust. Because the soil of the right-bank middle terrace consists mainly of sand and gravel, the first plantings were mostly mixed woodland with many conifer stands; pines and birches grow best on such poor soils. Several decades later, the forestry authority began gradually converting the woodland into broadleaf forest. Since natural nesting sites are scarce, many nest boxes were put up. A forest fire on 21 April 1996 affected only a small part of the woods, which have since fully recovered.

On the northern edge of the forest, near the city boundary with Leverkusen-Schlebusch, lies the "Am Hornpottweg" nature reserve. This former gravel pit developed in the 1980s, a few years after it was decommissioned, into a habitat for numerous animal species, especially birds. Alongside resident birds, many migratory species use the pit as a resting place. A circular path runs around it and offers good观察 points for birdwatching. In Bergisch Gladbach, near the district of Schildgen, the "Nittum-Hoppersheider Bruch" is another nature reserve within the Dünnwalder Wald.