Development

Peberholm is considered to be a biological experiment. Scientists predicted that nature would colonise it and make the island flourish on its own, without any human interaction whatsoever. As of June 2007, scientists from the Biological Society of Lund had registered 454 species of plants on the island.^[3] Also resident to the island as of 2005^[update] were about 20 species of spiders, and approximately 12 species of birds.^[4]

Since 2008, both the quantity of birds and the number of bird species have seen an increase, and now between 20 and 30 species breed on Peberholm regularly. The island is largely inhabited by several kinds of breeding gulls, and some locally threatened species have also found a home here as breeders, including the Mediterranean gull and European rock pipit in some years. Many geese, ducks, great cormorants, and waders rest on the small island and the White-tailed eagle is often observed here in winter. The European green toad, which is rare and protected in Denmark,^[5] was found living in several ditches. In 2007–08 a count found c. 2,500 individuals, which is among the largest populations in Scandinavia. It is assumed that toads from Saltholm have swum across. Three species of mice have also populated Peberholm, from very early on, and since 2010, hares have crossed the ice from Saltholm as well and are now breeding on Peberholm. It is important to keep these populations under surveillance, as mice in particular are known to be potentially dangerous to the rails stability.^[6] From 2015, white rabbits too have been seen. They are assumed to have been released from someone's car.^[7]

In the years 2004–08 surveys focused on insects registered a total of 345 beetle species, 421 species of butterflies, and 18 species of bees. This is considered a relatively low diversity compared to similar habitats of Denmark and Sweden. Still, some of the species found on the island are rare or threatened in the region. The population of butterflies seems peculiarly skewed towards regionally uncommon or rare species, including Epiblema grandaevana (a species of moth), and Bath White (Pontia daplidice). In 2005 the Hobo spider was discovered here, a spider that is only regionally known from a certain spot in Jutland. It is thought that it migrated here by trains from abroad. In 2006, the weevil species Ceutorhynchus resedae was also discovered, a unique find in Denmark.^[6]