The lowlands of Hokkaido, the northernmost of the four main islands of Japan, represent a transitional zone between cool temperate forests to the south and subarctic forests to the north. The lowland deciduous forests of the island form an ecoregion consisting of oaks, basswoods, ash, and conifers with a dwarf bamboo understory. While there is very little endemism, the ecoregion contains a number of northern Endangered species of that are not found in the rest of Japan, including Blakiston's fish owl (Ketupa blakistoni). Logging, overgrazing, poaching of wildlife for subsistence purposes threaten the remaining habitats.
Location and General Description
This ecoregion covers the low hills and plains of Hokkaido in the Japanese archipelago, and covers all of Hokkaido north of the Oshima Peninsula. The island faces the Sea of Okhotsk and is separated from Honshu by the Tsugaru Strait and from Sakhalin by the Soya Strait. The lowland deciduous forests of the island are dominated by species such as oaks (Quercus – especially Mongolian oak (Quercus mongolica)), basswoods (Tilia), and ash (Fraxinus), typically with a Sasa (dwarf bamboo) undergrowth. Hokkaido represents a transitional zone between cool temperate forests to the south and subarctic forests to the north, with the exception of the Oshima Peninsula. The base of the Peninsula forms a boundary known as the Kuromatsunai line. Cold winter temperatures to the north of the Kuromatsunai line prevent the establishment of beech forests in this region.
Hokkaido has an average temperature of eight degrees centigrade and receives an average annual precipitation of 1,150 millimeters (mm).
The faunal diversity in this area is relatively low, and there are no endemic species.
More than 200 species of birds are found in the ecoregion. Hokkaido contains a number of bird species associated with northern latitudes that are not seen in the rest of Japan, including Vulnerable Stellar’s sea eagle (Haliaeetus pelagicus), white-tailed sea eagle (Haliaeetus albicilla), common merganser (Mergus merganser), tufted puffin (Lunda cirrhata), hazel grouse (Tetrastes bonasia), three-toed woodpecker (Picoides tridactylus), and willow tit (Parus palustris). An endemic sub-species of hazel grouse (Tetraste bonasia vicinitas) is also found in the ecoregion.
The Endangered red-crowned, or Japanese crane (Grus japonensis) is considered a Natural National Monument. The Hokkaido red-crowned cranes are resident year-round on the east coast of the island while the mainland populations of red-crowned cranes are migratory.
Blakiston's fish owl (Keputa blakistoni) is a rare, Endangered bird found in this ecoregion. With a very limited range, it range is believed to be from the Hidaka mountain range to Nemuro and the Shiretoko Peninsula. This species is listed as a natural monument though no habitat has been specifically designated for it. Approximately 120 individuals are found in Hokkaido, though perhaps 1,500 birds combined are found in Russia and China.
There are approximately 37 species of mammals in the ecoregion. These are mostly small mammals such as microbats, rodents, rabbits, and small mustelids. Red foxes (Vulpes vulpes) are present. There is an Endemic subspecies of the more widespread Sika deer (Cervus nippon yesoensis) which the IUCN considers Data Deficient.
Hokkaido is the only portion of Japan which supports a population of brown bears, and the Hokkaido brown bear is considered a subspecies (Ursos arctos yesoensis) which is also found on the neighboring Russian controlled islands. The brown bear is an area-sensitive focal species for conservation planning in the ecoregion. There are five subpopulations on the island, and they are quite restricted in their distribution in the lowland ecoregion where they tend to overlap with human areas.
The conservation status of these ecotone forest communities is not satisfactory. Only thirty percent of the Blakiston's fish owl nesting sites are protected within National Parks or Wildlife Protected Areas and there is no regulation for general protection of the owl habitats. Excellent stands of the mixed forests have mostly been exploited for logging and the remaining forest communities have heavily been affected by grazing of horses and cattle. Rapid population decline of the endemic hazel grouse subspecies has been observed in the past three decades possibly due to the replacement of natural deciduous mixed forest with pine plantations. The most prominent examples of intact tracts of this forest ecoregion are found in the state reserves of Mt. Moiwa and Maruyama Hill in central Hokkaido.
Types and Severity of Threats
Logging and overgrazing are the two main causes for habitat destruction. The poaching of wildlife for subsistence purposes and harvesting of plants for traditional medicine are also major threats to wildlife.
Habitat loss and degradation, in the form of continued agricultural and industrial development constitute the principal threats to red-crowned cranes in Hokkaido. However, two active habitat management measures have allowed the Japanese red-crowned crane population to increase: winter feeding stations and the installation of conspicuous markers on utility lines. This latter action has reduced the rate of mortality from collisions approximately 60%.
On Hokkaido Blakiston’s fish-owl is threatened by traffic collisions, powerlines, and drowning in fish-farm nets.
Brown bears on the island are impacted by hunting for sport and damage control as well as vehicular collisions, but the greatest threat is the conversion of hardwood habitats into conifer plantations. The bears’ distribution has been contracting and there is evidence that annual harvests exceed sustainable levels. Efforts directed at public education regarding human-bear interactions and the need to conserve and plan around bear habitat have been identified as priorities.
Justification of Ecoregion Delineation
Hokkaido is the northernmost of Japan’s four main islands. The ecoregion consists of deciduous forests in the lowland areas dominated by Mongolian oak (Quercus mongolica) with dwarf bamboo (Sasa spp.) undergrowth. It belongs to the transitional zone between cool temperate and subarctic, which extends to the north of the Oshima Peninsula, the so-called Kuromatsunai line. Cold winter temperatures to the north of the Kuromatsunai line (through Suttsu, Kuromatsunai and Oshamanbe) prevent the establishment of beech forests in this region. The boundary of this ecoregion follows the Saso-Fagion crenatae region in Hokkaido from Miyawaki’s Potential Vegetation Map of Japan. The line between Hokkaido and the Japan Sea floral districts in Shimizu corresponds to the southern boundary of the ecoregion.
Additional Information on this Ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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- Environment Agency of Japan. 1992. Nature conservation in Japan: the 3rd Edition.
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- Numata, M., editor. 1974. The flora and vegetation of Japan. Kodansha, Tokyo, Japan.
- Servheen, C., S. Herrero, B., Peyton, (compilers). 1999. Bears, Status Survey and Conservation Action Plan. IUCN/SSC Bear and Polar Bear Specialist Groups. IUCN, Gland, Switzerland & Cambridge, UK. ISBN: 2831704626
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