Ecosystems recover in tidal flats hit by tsunami

A Tohoku University research group has found that the ecosystems of tidal flats off the Tohoku region in northeastern Japan have largely recovered since the devastating tsunami of 2011.

The group led by Professor Urabe Jotaro researched aquatic life in 11 tidal flats off Fukushima, Miyagi and Iwate prefectures with the help of local people.

The average number of species fell by about 20 percent to 32.3 after the tsunami. It rose to 58.8 in 2013, then fell again before gradually increasing to reach 56.5 in 2019.

The figure is about 40 percent higher than before the tsunami, and increases were seen in all 11 locations.

In Hitsugaura Tidal Flats off Rifu Town, Miyagi Prefecture, the number of species fell by about 20 percent after the tsunami, but increased greatly with the addition of new species such as gazami crabs and breadcrumb sponge.

The number reached 44 in 2019 after rare tideland and shore snails were found. The snails are designated by the Environment Ministry as an endangered species.

Urabe says the tsunami may have reset ecosystems throughout the tidal flats, making it easier for many species to live. Meanwhile, global warming may have made it possible for new species to migrate and settle in the area.

He says tidal flats are a broad source of various marine organisms that warrant continuous research.