Peat swamp forests occupy the entire coastline of Borneo. The soil of the peat swamp is comparatively infertile, while it is known to be the home of various bird species such as the hook-billed bulbul, helmeted hornbill and rhinoceros hornbill. There are about 15,000 species of flowering plants with 3,000 species of trees (267 species are dipterocarps), 221 species of terrestrial mammals and 420 species of resident birds in Borneo. There are about 440 freshwater fish species in Borneo (about the same as Sumatra and Java combined). The Borneo river shark is known only from the Kinabatangan River. In 2010, the World Wide Fund for Nature (WWF) stated that 123 species have been discovered in Borneo since the "Heart of Borneo" agreement was signed in 2007.