A Case of Utilizing Results

Preparation of "Manual for Evaluating the Invasiveness of Plants
Introduced to Rivers" (Draft, tentative title)
OGURI Hitomi, Senior Researcher; HATASE Yoriko (PhD), Visiting Researcher; KURIHARA Masao ,Head
Landscape and Ecology Division, Road Department
Keywords: alien plant, invasive risk assessment, river management
1. Background "Manual (draft)" preparation
In the "National Strategy for the Conservation andSustainable Use of Biological Diversity 2012-2020" (Sep.
2012), as one of the national targets of Japan to achieve
the Aichi Target, it is required to develop an "InvasiveSpecies List" and "Invasive Alien Species Control Action
Plan (tentative)” by 2014, so discussions are underway
accordingly.
In riverbeds, many plants including alien plants areused for levee armoring, planting in river parks, etc.
(Figure). Some alien species are invasive and escapefrom the originally seeded / grown area, whereby
affecting native species and ecosystems. Therefore, whenusing an alien species as a garden plant (Photo) in ariverbed or afforestation project, it is necessary to grasp inadvance its escape and settlement risks.
Therefor, as reference material for selecting plants that
do not impact the natural environment or rivermanagement, we developed a "Manual for Evaluating theInvasiveness of Plants Introduced to Rivers" (draft,tentative title). It organizes the concept of priorassessment in introducing new species, points of attention
in introduction and management, etc.
2. Outline of "Manual (draft)"
The "Manual (draft)" first organizes the concepts of

Afforestation plants

Afforestation plants(Alien)8% (21 species)

3. Publication of findings
The "Manual (draft)" will be released to the public as
an NILIM document.
(http://www.nilim.go.jp/lab/ddg/seika/)
We hope that this material will contribute to alien species
control measures at actual sites.

Unknown (Lawn不明（芝類）
grasses)
1%（1種類）
1%(1 species)

緑化植物（在来）(Native)3%（8種類）
3% (8 species)

Garden plants, etc.
(Native)
24% (63 species)

invasiveness including the necessity for considering it,
and then introduces how to assess invasive risk including
assessment methods in other countries. Furthermore,
the Manual describes the species that warrant attention
based on the results of the Census of Rivers and Riparian
Areas, and points of attention in using garden plants andafforestation plants.
Ten percent of the introduced plants are said to escapeto outer fields, and 10% of those species are said to settle
and a further 10% of them are said to become invasive.
Therefore, many of the alien plants used may not beinvasive. However, even if the quantity of alien plants isvery small at first, they are likely to increase enormously
as time elapses. In such case, they are regarded as"invasive alien species," which escape and settle in thenatural environment and adversely affect ecosystems andhuman activities. It will become very difficult to eradicate
them if they expand across a wide area. It is, therefore,
important not to use alien plants with high risk of escapeand settlement from the beginning.

Garden plants(Alien)56% (146 species)

Vegetables / Edible
plants8% (20 species)

Figure: Number of Species of Herbaceous
Plants Seeded / Grown in Japanese Rivers
from 2005 to 2010

Photo: Example of Garden Plants Growing inRiverbed(Left: Verbena hybrida, Right: Forget-me-not)