There are many protected areas on Bornholm, and the conditions here have enabled not only unusual plants but also animals to thrive.
The landscape on Bornholm has been influenced by human activity over the past 10,000 years. Stone Age and Bronze Age peasants burned the forests to adapt the land for farming and grazing. During the Iron Age, most of Bornholm was used for agriculture. Over the last 100 years, the natural landscape in non-forested areas has shrunk intensively due to the development of agriculture. The development of built-up areas, extraction of natural resources and planting of fir forests have also contributed to the reduction of natural habitats on the island.
Most of Bornholm is now used for agriculture. Huge cultivated fields leave no room for natural, primeval nature.
The east, north and west coasts of the island are rocky, with cliffs up to 80 m high (the massif of the northern tip of Hammeren), while the southern coasts are formed by wide, sandy beaches. The northern and central parts of the island are hilly, while the southern part is mostly flat and dunes. The highest elevation, Rytterknaegten, is 162 metres above sea level and is situated in the centre of the island. Several short rivers flow through the island (some are intermittent), the longest of which Øle Å is 22 km long. There are also several small glacial or mine-lined lakes on the island, the largest of which is Hammerso (650 m long, 150 m wide and 13 m deep).
Bornholm has a very varied landscape. Particularly impressive are the rocky coastlines, such as Jons Kapel, north of Hasle, North Cape Hammeren and almost the whole north coast of the island from Allinge to Svaneke. Along the north coast, the bedrock emerges directly from the sea and rises steeply upwards. Although the north and east coasts are in the form of high cliffs, in some places small sandy beaches, coastal meadows and reed swamps can be found between the low coastal cliffs.
The southern part of the island is covered with dunes and vegetation. From Nexo and Snogebaek, the sandy coastline is low and wet, but further west towards Dueodde it becomes a kilometer-wide dune coastline of fine sand. The sandy beach extends westwards. Instead of wide dunes, there is a sandy cliff that is gradually eroded by the sea and blown away by the wind.
The island owes its present appearance to glacial activity, which took place twice 15,000 and 12,000 years ago. Characteristic of the glacial advance are the rift valleys, the largest of which, Ekkodalen and Døndalen, were created by tectonic fractures. These rifts were deepened by the advancing glacier and their upper edges smoothed by the ground moraine. As a result of glacial erosion, there are also numerous smoothed granite hills in the northern part of the island and numerous erratic boulders and pebbles. The complexity of the geological structure of the island makes it highly diversified in terms of landscape and mineral resources, which are the basis of the local industry and handicraft.
Streams have formed in the rock chasms, which have their origin in the higher parts of the island, from where they flow into the sea. The deep valleys of the clefts protect from the wind in winter and provide shade and coolness in summer, creating excellent conditions for the development of fauna and flora.
Until the mid-18th century a large part of Bornholm was covered with heath. This was a typical cultural landscape, a result of cattle grazing in the central part of the island. There are still isolated fragments of heathland that have been preserved.
Thanks to conservation efforts, you can experience the atmosphere of old times in the open areas of Hammerknuden. In Paradisbakkerne and the central part of Rutsker Hojlyng, attempts are being made to preserve the remains of the original wild heathland for future generations. Balkalyngen heath, Denmark's only sandstone heath, is a great rarity.
Bornholm is the most forested county in Denmark. More than 20% of the island is covered by forest. Almindingen, with its adjacent forest plantations, is the third largest forest complex in Denmark. Situated on a bedrock it towers over the surrounding area. Much of Bornholm's forest was planted on the site of former heathland.
However, there are places on the island along the coast and along the many streams where fragments of original forest remain, with a mixture of Bornholm's characteristic hornbeam and cherry trees. In addition, there are plenty of small woods and gallery forests along the creeks and streams.
Hammerso is actually the only large lake on Bornholm, and the only lake in Denmark with a mountainous character.
However, there are many marshes and shallow lakes, both in the open and in the wooded areas. Peat was extracted from the marshes in many places during World War II, and the small, undeveloped lakes are a remnant of this.
The lakes, ponds and marshes are home to a variety of often rare organisms. An unforgettable impression is the possibility to observe the mating dance of cranes or the concert of water frogs on a moonlit spring night.
The Bornholm subsoil contains interesting and very varied geological deposits, which form the basis of the local quarrying industry. Granite is quarried for monuments, road-building, water-building and gravel. Limestone and sandstone have been used in house building and cement production since the Middle Ages.
Many places on the island produce building materials based on gravel and clay. Charcoal was used as fuel during both world wars. Feldspar, which is used to make glass, kaolin, which is used to make porcelain, phosphorite, which is used in fertilizers, and alum, which is used in leather tanning, are among the many special industrial raw materials found on Bornholm.
Copper has also been found in the Bornholm subsoil but has not yet been exploited. Numerous industrial pits and quarries are scattered around the island, creating a specific "cultural landscape". Many of these pits are filled with water or overgrown with vegetation. Others show deposits from different geological periods and thus offer an opportunity to get to know the geological history of the island.
The terrestrial fauna of the island is similar to that of Denmark and southern Sweden. An artificially bred mammal species is the fallow deer. The island is known for its large number of large hedgehogs, which are sometimes a problem (especially at campsites).
The ornithoid fauna is rich, mainly represented by sea birds and birds migrating from Scandinavia. Ornithological reserves are located around Nexo and on the island of Graesholm (within the Ertholmene archipelago).
Bornholm has herring, cod, salmon, sea trout, flounder and other Baltic fish.
Bison were also brought to Bornholm from Poland. Thanks to a new way of listening for bats, the existence of six new species of these mammals has been discovered in the last 10 years. Bones of many animals have been found on the island, including reindeer, deer, beaver, wild boar and marten.
The island is known for its gentle roe deer and they are hunted here unusually often, deer have large antlers here.
Birdlife has been well studied here, with more than 100 new species discovered every year. Two genera in particular, namely the Grey Nightingale and the Rook are more common here than elsewhere in the country.
The migration of the Black Woodpecker to the island in the early 1960s brought an increase in the number of hollows in the forests, which favors breeders of birds such as jackdaws, pigeons and owls. There are more and more of them, and Bornholm is the only known breeding ground for them. The migration of birds in spring and autumn on the island is enormous, especially flocks of cranes and wagtails, which makes the island unique. In warm springs, the island is visited by migratory birds such as the common pochard.
The reptile fauna is not very different from the rest of the country and only 5 species are well reproduced. Most of them are found in the moors in Hammerknuden. There are nine types of amphibians here. The dusky frog is found throughout Denmark, with only on Bornholm are half of them found in ponds on the island.