While down in the valley the diversity of nature already significantly changed from early in the Neolithic (first agriculture), the rocks make for a safe haven as here nature remains untouched for a long time. Eventually in the 20th century also the rock ecology is disturbed and pushed back to a minimum as the rock is 'cleaned' for climbing.

The impact of climbing is summarized as follows:

The opening of these routes and their maintenance led to the destruction of the vegetation that was deemed annoying. Moreover, earth (that over centuries had slowly formed) was extracted from ledges, cracks and other cavities. The repeated passage of climbers on the limestone walls planes the vegetation and disturbs the birds which nest in the cavities. Finally, the trampling of the top of the rocks leads to destruction of specific vegetation making banal and ruderal species overtake the places." (usually nettles and thorny blackberries)

Paradoxically, the fauna of the Freyr rocks has been little studied so far and the available data are sparse. Only a few species of vertebrates and insects are cited by BUNGART and SAINTENOY-SIMON (2008).

On obsirocbel.com Guy Bungard approaches the impact of climbing carefully, gathering numerous studies:

The reality is complex. The government lists a series of measures taken by the Club Alpin Belge. Elephant paths need to be discouraged, thorns and ivy pulled (recently done on Fromage) and bird nests need to be signaled. Guy's personal account of the authorities' and exploiter's protection is sceptical:

Whilst in some countries appropriate signage seems to offer sufficient protection, we must note that this is not the case in our country, where since 1997, as active observers, we conduct an Information Policy towards the authorities without any significant results. In fact every year we observe that protected species are deliberately uprooted or trampled. - Guy Bungart 6 December 2015

From my own perspective I have been quite disappointed from the few times I reported a nest on Jeunesse. Only seldom an indication is made with a lint, hardly bothering the series of student clubs that booked Freyr. It is also said abseiling and the use of the top rope should be regulated (and if not for ecological reasons then at least for safety), but it remains a common practice of groups, even of the military government. It is time to communicate with the military, time to demand visible contributions from said student clubs, like cleaning the trash and clearly educating their groups.

On several policy levels the site 'Valléé de la Meuse d'Hastière à Dinant' has been established as a region that deserves specific attention. Lots of rocks outside of Freyr remain strictly protected, as well as parts of rocks at the level of Freyr itself.

There are numerous assessments available on the biological riches around Freyr. Biologists of Wallonia's territorial government have delineated several zones where a part of former complex ecosystems is preserved. The rocks of Freyr are sites de grand intérêt biologique (SGIB), which means they're shelters for threatened species and biotopes, making the rocks the heart of the main ecological structure.

Despite the climbing still some specific flowers grow at the base of the rocks, or sometimes in the middle of the climb. Remaining patches of ecologies have been designated Natura 2000 status. E.g.: on top of Cinq ânes is a very unique partly-intact and vulnerable calcareous grassland. In the middle of Merinos is a comparable habitat. Le Ravin du Colébi south of La Jeunesse is not accessible and strictly protected.

Recently the lush forest turned morbid. A majority of the ash trees stuck out dead branches through the canopy. Several fell down and turned the soil up. Culprit is the funghus Hymenoscyphus fraxineus that comes from China and started its advance in Belgium in 2010.

The region is the home of protected fauna. Selected indicating species that are robust yet rely on a (to some degree) diverse thriving ecosystem:

  • Eurasian eagle-owls

  • peregrine falcons

  • kingfishers

  • greater and lesser horseshoe bats

  • Geoffroy's bats

  • pond bats

  • thick shelled river mussels

  • Amur bitterlings (fish from the carp family)

  • Cottus Perifretum which is often referred to as the European Bullhead but is a seperate species known as 'chabot' in French and 'rivierdonderpad' in Dutch

  • brook lampreys (snakelike fishes)

  • Jersey tigers (a colorful day-flying moth)

  • and Northern crested newts.