Although Flanders is not richly endowed with vast old-growth forests and other pristine habitats, the number of nature reserves and protected areas is steadily growing. The majority of these areas and reserves, however, have not met all the requirements set out by the EU in its European Habitats Directive. That said, the Capuchin forest surrounding the arboretum allows the visitor to experience certain types of habitats and ecotopes that nearly meet the EU’s directives. Rejuvenated towards the end of the 19th century, the oak forest here is fairly old and is home to other tree species such as ash and beech. Also in the mix are elm and lime trees, and here and there are cherry trees and species of birch. Less natural are the younger stands of coniferous trees like Douglas fir, hemlock, and Westen red cedar, species that nonetheless make the landscape more attractive. Black pine grows on the sometimes steep, sandy slopes on the south side, adding more charm to the domain. The hardy Scots pine is also very much at home here. On the Keienberg area, an open space has been designated as Brabant heather, a semi-natural landscape type that used to be more common here and that was grazed by sheep.
Needless to say, the arboretum is not an example of a local ecosystem, but the meadows in between are nonetheless noteworthy from an ecological standpoint. And important, too, because they happen to be rare. They can be classified as a type of species-rich Nardus grassland. These meadows are not very flowery or colorful at first sight, but there are areas here that are full of species that we would typically find in such habitats: varieties of Tormentil, a herbaceous perennial plant, trailing St John’s-wort, heath bedstraw, and other smaller plants of modest flowering.
Lurking in the forest and crawling across the grass leaves, less visible to the eye, is a teeming insect fauna. Certain butterflies are easier to spot on the grasslands, such as the ringlet butterfly and the so-called meadow brown. In the forest, with some luck, the visitor might spot the striking silver-washed fritillary. Higher up, in the quiet shelter of the treetops, are the purple hairstreak and the graceful purple emperor butterfly. The best time for birdsong is the morning. In the evening the visitor can hear the Tawny owl hooting. Hungry buzzards, sparrowhawks and a single goshawk seek prey throughout the day. Breeding on the scattered pools here and there are various types of frogs, toads and salamanders.
Foxes and roe deer make up the bigger mammalian fauna. The best time to see a family of roe deer or a solitary roebuck is early in the morning or just before dusk. A recent newcomer here is the wild boar. In principle, a large forest can certainly accommodate wild boars searching for a place to live, but this gets problematic in the Sonian urban peripheral forest, with its intensive recreative use and its nearby traffic roads and residential areas. If you encounter a wild boar, it is best to keep calm and refrain from approaching or teasing the animal. Keep out of its way. A wild boar is not aggressive by nature. They are rather shy. But, like any frightened animal, they can be dangerous if they feel threatened or harassed.