Alongside its many beautiful areas of pre-alpine moorland, the biosphere reserve has earned UNESCO recognition for its unique karst landscapes.
Situated within the strictly protected core zone, the «Schratteflue» – the most striking karst mountain in the biosphere – is one of Switzerland’s prime karst landscapes. From a distance, it appears to be almost completely devoid of plant life, and indeed vegetation is sparse. The Schratteflue is impressive not only for its strange karst formations above ground, but also for its extensive underground cave system. Owing to the hole-filled surface, water trickles straight into the depths and drains into the huge and highly complex underground water network.
Pretty cushion plants and alpenrose (known locally as «Steiröseli») grow on the Schratteflue. On the north face, the rugged, steeply sloping rock faces with large gravel fields merge into alpine pastures and moorland. Thanks to its range of habitats, this area supports a wide variety of animal and plant species.
Karst describes an area of land mainly made up of limestone. The appearance of the rock in karst areas is created by weathering from slightly acidic rain, which erodes the soluble limestone and forms myriad patterns and hollows. The Schratteflue is the global type locality for the Schrattenkalk Formation, marine sediment from the early Cretaceous period (‘type locality’ indicates that a rock or mineral was scientifically documented for the first time at this particular location). Embedded in the Schrattenkalk Formation are numerous fossils (petrified mussels and other sea creatures) from a primaeval sea.
The limestone layer has an average thickness of 80-100 metres. The pavement of Schrattenkalk limestone features highly intricate surface patterning: karren, razor-sharp rillenkarren (‘Schratten’), dolines (sinkholes) and much more.
The Schratteflue range is made up of sediment from the ancient Tethys sea, deposited in northern Italy some 100 million years ago and transported north as the Alps formed. As the Alpine divide formed, marine sediments were driven over the layers to the north, which explains why the Schrattenfluh resembles an oblique plate sloping sharply northwards. Plant life on the limestone pavement of the Schrattenfluh depends on altitude, with the lower elevations forested with conifers and deciduous trees. Above the tree line, moors alternate with meadows. At its highest elevation, the limestone pavement is completely devoid of vegetation. This gradation is partly due to a lack of ice coverage at higher altitudes during the last ice age.
The Schratteflue is home to a widely branching cave system over 50 kilometres in length. Although almost all of the caves are difficult to access and closed to the public, explorers have found interesting remains of bears, moose and other vertebrates in many of the caves. In the course of cave explorations in 1969, a small insect was discovered which has only ever been found in the Schratteflue: the pseudoscorpion Pseudoblothrus thiebaudi, which measures just 2mm. The caves also provide an important wintering site for bats. Guests can visit the Silwängen cave and see its bizarrely shaped stalactites on a guided excursion.
Various speleologists have studied the many fissures of the Schratteflue since 1959. The largest cave, the Neuenburgerhöhle, was discovered very early on in these explorations and named after the home base of the explorers. Spanning 7.5 kilometres, it remains the longest cave found in the karst region to date. With many other caves ranging in size and depth, the Schrattenfluh conceals an unimaginably large water network. Rain takes just seconds to trickle through the exposed holes of the limestone pavement, draining as far as the underlying impermeable layer of stone (Drusberg marl) before disappearing into hidden subterranean streams and rivers. In the course of a water tinting exercise in 1970, it was found that water coloured in cave P55 (in the middle of the Schratteflue) did not, as expected, reach the inlets of the large Emme or Waldemme rivers, but travelled an incredible 20 km underground before emerging in Lake Thun 38 hours later. By contrast, more recent studies have shown that eastern parts of the Schrattenfluh drain into the Waldemme as expected.