## V egetation Changes

In order to understand the changes in the vegetation in areas submerged by the tsunami along the Pacific coastline from Aomori Prefecture to Chiba Prefecture (about 576 km $ ^{2} $ ), we created vegetation maps before and after the earthquake (November 2012) and then overlayed them to compare the changes before and after the earthquake.

A scale of 1/10,000 was assumed for the plot accuracy up to a distance of about 500 meters inland. Thereafter, a scale of 1/25,000 was used further inland.

## Pattern of change due to the tsunami

## Pattern of change

Example ① Remained Forest (50% or more remained)

Example ⑩ Flowed out / sink

$ ^{*} $ Aerial Photos: Taken by Geospatial Information Authority of Japan

## Changes in the Vegetation

Change in area

Based on all the areas in the six prefectures, “Changed to barren land” areas (where weeds grow abundantly in areas damaged by the tsunami) occupy the greatest share at 30% of the total area. This is followed by “Changed for artificial use” (e.g. developed lands and debris storage areas etc.) which occupies 10% of the overall area. Due to the concern over the potential invasion by invasive alien species in these areas, monitoring of the trends is thus required in future.

## Akasaki coast (Kesennuma City, Miyagi Prefecture

Before the earthquake, sandy beach, sand dune vegetation and Black pine plantation could be seen along the shoreline while paddy fields and farmlands extended inland. After the earthquake, the sandy beaches, sand dune vegetation and coastal forests disappeared and the shoreline receded. In addition, the paddy fields and farmlands became vacant site covered in weeds, uncultivated field areas and debris storage site.

After classifying the change patterns and vegetation damage status based on the maps before and after the earthquake, we found that many of the coastal and river bank areas have been submerged or washed away, while many inland areas have become barren lands or have been transformed for artificial uses.

## Before the earthquake (May 2001)

Paddy fields (light blue)

Inlands areas were mainly cultivated as paddy fields.

Phragmitetea (sky blue)

Reed (Phragmitetea) typical of the vegetation around rivers were seen from the river shores to the river mouth.

*Geographical map: 1/25,000 map of Geospatial Information Authority of Japan

## After the earthquake (June 2011)

## Changed to barren land (orange)

In paddy fields which have become uncultivated fields, plants that thrive in wet environments such as the Typha latifolia have grown in abundance. Some of these are observed to be rare species facing the threat of extinction. Future trends need to be monitored carefully.

Monochoria korsakowii (near-threatened species)

Photo taken in September 2012

*Aerial Photos: Taken by Geospatial Information Authority of Japan

## Sand dune vegetation (light purple)

Vegetation specific to sandy beaches such as the Carex kobomugi and Calystegia soldanella used to grow along the beaches. The scenery from the beach to the coastal forest looks beautiful and the beach has been used by local people for recreational activities for a long time.

## Coastal forests (green)

Black pine (Pinus thunbergii) forests could be seen behind the sandy beaches. The Black pine forest of the Akasaki coast have been designated as a “Preserved forest for tree genetic resources” by the Forestry Agency.

## Newly-formed sandy beaches (beige)

Although the vegetation is returning along the sandy beaches after the earthquake, invasion of invasive species has also been observed at the same time. The future trend needs to be monitored.

Invasive species, Cakile edentula (Photo taken in August 2012)

Flowed out / Sink (Red)

A large part of the coastal forest and sand dune vegetation have disappeared from these flooded areas. In the Sanriku area that have been devastated, most of the vegetation in the sand dunes were washed away together with the sandy beaches.