A challenge to dam improvement for the protection of both salmon and human livelihood in Shiretoko,Japan’s third Natural Heritage Site |
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Authors: | Futoshi Nakamura Eishige Komiyama |
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Institution: | (1) Laboratory of Forest Ecosystem Management, Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo 060-8589, Japan;(2) Wild Salmon Laboratory, Aza-Yobihito 159-119, Abashiri 099-2421, Japan |
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Abstract: | The Shiretoko Peninsula was placed on the World Heritage List in July 2005 as Japan’s third Natural Heritage Site, being valued
for its unique ecosystems formed by the interaction between marine and terrestrial environments. Prior to its listing, however,
the International Union for Conservation of Nature and Natural Resources requested the development of measures to allow for
the free movement of salmonids through the nominated area via artificial in-stream structures. This report introduces a pioneering
effort to modify check dams in order to improve ecosystem linkages. The River Construction Working Group has intensively discussed
and implemented restoration projects for 3 years, and the results have been monitored after implementation. Of 44 streams
within the Shiretoko World Natural Heritage Site, 14 streams have had one or more in-stream structure(s) built. A total of
123 structures, mainly soil conservation dams, are distributed sporadically in these streams. Following assessment, the Working
Group concluded that it would be reasonable to modify 31 structures in five streams, including 18 structures that were to
be modified before listing. The most suitable design that met local stream conditions was selected, after accounting for salmon
passage, adverse impacts on stream environments above and below the construction sites and on fishing grounds, efficiency
of construction, and ease of postmodification maintenance. Working in cooperation with the group members and parties concerned,
we succeeded in restoring salmonids’ upstream runs and extending their spawning habitat in streams above some of the dams,
while keeping the disaster prevention function of the dams intact. |
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