ASIA ENVIRONMENTAL INITIATIVE 2016: JAPAN
Sato -Umi "里海”
Sato (里) means human area or community, while umi (海) means sea.Thus, sato-umi is an area of sea influenced and maintained by people.
The overall concept of sato-umi is to establish a symbiotic relationship with human communities and the ocean in order to be both sustainable and productive.
Eelgrass and Sato-Umi
In the Seto Inland Sea, efforts to restore eelgrass (Zostera marina) are being initiated by the local community. After World War II, a large decline in eelgrass (amamo in Japanese) was seen, falling from 590 hectares in 1940 to only 12 hectares by 1985. Eelgrass acts as a nursery habitat for juvenile fish. This directly effects fisheries, as the eelgrass beds protect younger fish as they grow. Thus, the local fishermen of the Seto Inland Sea were the first to notice the effects of eelgrass on their fisheries. Without a nursery habitat, fish stocks were quickly depleted. The local fishermen concluded that to support their fisheries, they needed to restore local eelgrass habitats.
Eelgrass restoration began as an experimental, grassroots effort, that became a largely community-driven force. Science has allowed newer, more efficient methods of eelgrass replanting to be developed. Eelgrass restoration is now run in a two phase process that involves collection in the Spring and Summer, and replanting in the Fall. In the Spring, floating swaths of eelgrass become detached from the seafloor, floating to the surface. Fishermen collect the floating eelgrass by hand, then removing the seeds from the eelgrass. In the fall, the seeds can be thrown back into the waters, where they will take root in the sediment and grow new eelgrass.
During our time in Japan, we attended the Amamo Summit in Okayama, where we learned more about local eelgrass restoration efforts by assisting with Spring eelgrass collection. Not only did this give us hands-on field experience with eelgrass restoration, but also gave us an insight into environmental education in Japan, which is largely based on volunteerism and community involvement. Participants in the Amamo Summit included local fishermen, volunteers, elementary school children, college students, and more. Getting many people interested in environmental restoration in an active way, such as collecting eelgrass, has proven to be quite effective in Okayama, where eelgrass is making a comeback. This community involvement in the local marine ecosystem is a prime example of satoumi.
Eutrophication
Eutrophication is the build up of excess nutrients in a body of water; often causing algae blooms, anoxia, and mass fish mortality. The Seto Inland Sea of Japan is heavily influenced by eutrophication due to its semi-enclosed nature and industry. Industry and runoff provide the organic waste and nutrients while the semi-enclosed nature of the sea elongates their retention time. This often causes algae blooms which cause mass fish mortality due to toxins in the algae or subsequent anoxia. The consequences have drastically impacted the fishing industry in the Seto Inland Sea, with one mass death of yellow tails costing upwards of 7 billion yen. Due to these events the Law Concerning Special Measure for Conservation of the Environment of the Seto Inland Sea was passed in 1973 in order to restrict the amount of waste introduced by factories, sewage treatment facilities, etc. This law has successfully reduced the amount waste as well as algae blooms, though not back to pre-industrial levels.
A single blade of eelgrass contains many seeds, which can be seen in the image above.