Lead Scientist Travels to Japan; Explores Parallels to Delta

Delta Lead Scientist Cliff Dahm traveled to Japan recently to give a keynote address entitled, “Perspectives on Restoring the California Delta” to the Ecology and Civil Engineering Society of Japan. Dahm was invited by the Society to be this year’s international keynote speaker at its annual meeting in Sapporo, the capital of Hokkaido, Japan, where the theme of this year’s conference was “From the Forest to the Sea.”

“We look from the Sierra to the Bay; they look from the volcanic mountains to the Sea of Okhotsk,” said Dahm. While in Japan, he also discussed his three decades of research on streams and rivers of the western United States with graduate students, postdoctoral researchers, and young faculty in Hokkaido, the second largest of Japan’s four main islands.

Japan has more annual flood damage than any other country in the world. Devastating flooding has caused the Japanese to invest substantively in engineering projects to protect life and property in the lowland floodplains where Japanese live. Recently there has been growing concern to couple flood protection with sustaining some ecological function in their river ecosystems. The Ecology and Civil Engineering Society of Japan was formed to address flood protection and ecosystem concerns through the advancement of interdisciplinary science between ecology and civil engineering.

Dahm took two field trips during his stay-one to the Ishikari-gawa River, the second largest river in Japan and the research site of his hosts from Hokkaido, and a second trip to mountain rivers in Yobetsu on the Shakotan Peninsula. There he was introduced to cherry salmon, a Pacific salmon characterized by tiger-like red stripes, one of the research projects designed to evaluate the effectiveness of stream and river restoration for improving the status of cherry salmon over the long-term.

During the conference, Dahm learned:

  • Japan has a land area roughly six-percent smaller than that of California with more than three times the population of California. Japanese rivers are short(<370 km), steep, and flashy with annual flood damage the highest for any country worldwide. Japanese rivers have a rich freshwater fauna and flora, and Japanese human populations concentrate on the alluvial plains of these rivers.

  • River and wetland restoration is a major enterprise in Japan. More than 30,000 river restoration projects have been carried out over the past two decades, and restoration has become a major investment for improving Japanese rivers. The focus for restoration in northern Japan is on improving conditions for native salmonids.

  • When scientists think of restoration efforts, Japan is not the first country that comes to mind, yet Japan spends amounts comparable to the United States on restoration-approximately $15 billion since 1990. And although the total number of restoration projects in Japan is almost as high as in the U.S., the ratio of relevant scientific publications (in English) about stream and river restoration in international journals is about 1:100 compared with studies from the U.S.

  • Today, the conservation of aquatic ecosystems is of great importance in Japan and many measures have been implemented to slow or reverse the degradation of river habitat. In 2004, the Invasive Alien Species Act was implemented to eradicate certain invasive species and to regulate their import, dispersal, and spread.

Restoration of streams and rivers is a thriving business in both the U.S. and Japan. The Japanese are very interested in what we have learned about river restoration in the U.S. and in developing collaborations between our countries. Restoration projects often go unevaluated in both the U.S. and Japan. The scientists and civil engineers in the Ecology and Civil Engineering Society of Japan are firmly committed to learning through doing and in long-term assessment of the effectiveness of restoration projects that have been implemented throughout Japan.