(nsg.naturschutzinformation.nrw.de), is a nationally significant example of how man has created second-hand nature. On the one hand, gravel quarrying represents a strong intervention in the landscape and testifies to the dynamic transformation of nature by man against the background of economic interests. On the other hand, the sandbanks, shallow water zones and steep banks created by silting offer habitats for numerous plant and animal species, some of which have become rare, especially for waterfowl. The so-called Monbag Lake is listed, among other things, as a nationally important resting place for cormorants (Biological Station Urdenbacher Kämpe e.V. 2002 and biostation-d-me.de).
It is the largest of numerous other lakes that were created in the course of industrial mining of the raw materials sand and gravel in the city triangle of Monheim am Rhein, Leverkusen and Langenfeld and thus represent an anthropogenically shaped cultural landscape of quarry ponds. The other lakes include the three nature conservation lakes Klingenberger See, Oerkhaussee and Krapuhlsee and the smaller outcroppings of the Great Laacher See, Blue Danube, Buschbergsee, Hitdorfer See, Stöckenbergsee, Waldsee, small and large Dehlensee and the Widdu lake group.
The local raw material deposits were decisive for the settlement of industrial companies in the "stone and earth" sector, such as P. Odenthal's roof tile factory in Monheim in 1868, to which numerous quarry ponds can be attributed (Pracht-Jörns 2015).
The riparian shrubs and shrubs, gravel banks, bluffs and, last but not least, the bodies of water themselves deserve special mention as cultural landscape elements and structures worthy of protection for all lakes. If a near-natural state has been established, for example through renaturation measures, properly designed and planted quarry ponds can significantly increase the experience value of the landscape increase and also serve as important biotopes for flora and fauna (Kremer 1997).
While the nature reserves MonbagSee (with a few exception zones in the south), Klingenberger See and Oerkhaussee are not accessible, numerous excavated waters are now used for subsequent human use: they serve for recreation and leisure activities, for example as bathing lakes, for fishing or sailing.
(Maren Lenz / Biological Station Haus Bürgel - City of Düsseldorf - District of Mettmann e.V., 2019)