Stage 2 – Düsseldorf > Liège
With a total area of 570 ha, the Vallée de la Gueule Natura 2000 site, downstream from Kelmis, consists of several non-contiguous zones in the Three Frontiers region. Outside the forest, it also includes open environments, such as hayfields, meadowsweet pastures at the bottom of the valley, and calamine grasslands, as in Plombières.
A lead-rich ground
The Plombières site is a slag heap or calamine heap, that is to say, a deposit of mining residues, mainly lead and zinc.
How can such a site be a natural habitat? It is in fact a secondary habitat resulting from human mining activities and recreating the very particular conditions of an unusual primary natural habitat found on mineral-rich rocks, which have now disappeared as a result of their exploitation.
A calamine grassland
These grasslands are characterised by very low vegetation and the absence of trees or shrubs. On these contaminated sites, only a few plants manage to develop without completely covering the soil, large areas of which remain visible.
It is the presence of zinc and lead in large quantities in the soil that prevents trees from growing and leaves an open landscape. However, in some places, rainfall has removed part of the deposits, so the heavy metal content is lower and a clear forest of birch and willows takes its place.
Plants that love metal-rich soils!
Only a few plants manage to grow on these mineral-rich lands. Some grow only on these soils and dominate the most contaminated areas: these plants are called "metallophytes". Here we find the calamine catchfly, pennycress and fescue, the sea thrift and,especially, the yellow calamine violet. This small yellow flower blooms in a dense carpet between April and August.
Violets and butterflies
The yellow calamine violet welcomes the eggs and feeds the caterpillars of a pretty butterfly that can be observed in Plombières: the Queen of Spain fritillary. This butterfly can easily be recognised by the large, pearly spots on the underside of its wings while the top is orange, marked with round black patches. Fully protected in Wallonia, it lives in calamine grasslands but also frequents wastelands or wildlands rich in wild violets.
The Plombières site also hosts many other species of butterflies (more than thirty) as well as other insects such as bees and locusts. There are also many birds - along the river you can find the grey wagtail, the white-throated diver or the kingfisher hunting.