Ten years have passed since the Great East Japan Earthquake, and in the major tidal flats along the Tohoku coast that were severely damaged by the tsunami, the types of aquatic organisms such as shellfish and crabs have increased from before the earthquake, and the ecosystem is generally recovering. I found out by the investigation such as.
Survey of 11 major tidal flats in Fukushima, Miyagi, and Iwate
A research group led by Professor Jotaro Urabe of Tohoku University has been working on 11 major tidal flats in Fukushima, Miyagi, and Iwate prefectures to investigate changes in the coastal ecosystem affected by the tsunami caused by the Great East Japan Earthquake. Every year since the year of the earthquake, we have been investigating aquatic organisms such as shellfish and small crabs with the cooperation of citizens.
More species of organisms than before the earthquake in all 11 locations
As a result of summarizing the results, the average number of species of organisms that could be confirmed
was 32.3 in 2011 after the earthquake, which was about 20% less than before the earthquake, but in
2011,
it was 32.3.
Later, in 2013, it rapidly increased to 58.8 types,
then decreased again and then gradually increased. ▽ In the first year of Reiwa, the number was 56.5 types.
This was about 1.4 times that before the earthquake, and it was found that the number of species of organisms increased in all 11 places surveyed compared to before the earthquake, and the ecosystem was generally restored.
Of these, in the tidal flats of "Hitsugaura" in Rifu Town, Miyagi Prefecture, the number of species decreased by nearly 20% in 2011 due to the impact of the tsunami, but after that, Gazami and Namiisokaimen etc. With the addition of new species of tsunami, 44 species have been confirmed, including shellfish designated as endangered species by the Ministry of the Environment such as Kawaai and Batillaria zonalis.
Professor Urabe said, "It is possible that the tsunami once reset the ecosystem along with the tidal flat environment, making it easier for many organisms to live in, and global warming has led to the settlement of new species. The tidal flats are a valuable source of a wide range of children for various sea creatures, and we need to continue our research. "
"Benthos" is an important indicator of the status of the ecosystem
Aquatic organisms such as shellfish and small crabs that the research group has investigated are called "benthos organisms" and settle there and are susceptible to environmental changes, so they are part of the local ecosystem. It is an important index to know the situation.
However, there are many types of "benthos", and specialized knowledge is required to identify the species, and the results are likely to differ depending on the person investigating, and in many places in terms of human resources and costs. It is not easy to continue the investigation.
Therefore, the research group has developed a method to unify the method and time to investigate with the citizens, conduct a large-scale survey at multiple points along the coast every year, compare the results at each point, and make changes more accurate. I have been able to analyze it.
This survey is the only one that continuously surveys coastal organisms in the disaster area in the same way in various places.
As a result of summarizing the surveys so far, it was found that the types of creatures living on the tidal flats are almost returning to the state of each place before the earthquake after 10 years.
However, it is not completely the same in any place, and although about 70% of the confirmed species have settled, the remaining 30% are new species that appear occasionally but do not settle or appear very rarely. It was found that the ecosystem is being restored in the environment.