Hokkaidō is the second largest island of Japan and comprises the largest and northernmost prefecture. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel.
There are three populations of the Ussuri brown bear found on the island. There are more brown bears in Hokkaidō than anywhere else in Asia besides Russia. The Hokkaidō brown bear is separated into three distinct lineages. There are only eight lineages in the world. Those on Honshu died out long ago.
The native conifer species in northern Hokkaidō is the Sakhalin fir, The flowering plant Hydrangea hirta is also found on the island.