Assessing the Ecological Impact of Alien Species and Managing the Risks

Background and Objectives

With the enhanced trade of goods and the exchange of people with foreign countries, an increasing number of alien species is invading our homeland. Proliferation of alien species not only has an adverse impact on people�fs health and our agriculture, forestry and fishery, but also disturbs our indigenous ecosystem. For these reasons, the Invasive Alien Species Act was enacted in 2004 to eliminate alien species that have a serious impact on the ecosystem. However, an issue has been raised as to the uncertain standards to determine the invasive alien species to be controlled. Accordingly, there is a need to understand the degree of invasion by alien species already in Japan and assess their impact on ecosystem, as well as to develop risk assessment methodologies for yet-to-arrive alien species in order to suggest rational criteria for the designation of alien species to be controlled. In addition, techniques for the eradication of alien species already causing damage need to be developed.

Over the years, the National Institute for Agro-Environmental Sciences has worked together with other organizations to promote research on alien plants, insects and microorganisms (both unintended and intended) to contribute to smooth implementation of policy measures of communicable disease control. In addition, the institute has constructed the Asian-Pacific Alien Species Database to promote broad-range information gathering. Additionally, since 2005 a project titled “Risk Assessment for Alien Species and its Proliferation Prevention Measures” has been undertaken in cooperation with other research institutes in Japan as a project to resolve critical issues within the framework of the Special Coordination Funds for Promoting Science and Technology.

Burr cucumber (Sicyos angulatus)
(An Invasive Alien Species: its invasion of Japan was first recorded in 1952 and it proliferated subsequently throughout the country. Invasive Alien Species are subject to cultivation ban and eradication.)

Project Overview

Our research project consists of four parts: (1) to understand the latest situation of alien species affecting biodiversity and analyze the factors contributing to their settlement, growth characteristics and effects upon the ecosystem; (2) to develop risk assessment methods to evaluate the impact of alien species on the ecosystem, and to verify their validity; (3) to develop early detection and monitoring technologies by means of molecular marker and other techniques with respect to species that are difficult to identify; and (4) to develop technologies to eradicate, control or contain threatening alien species.

A good understanding of the actual situation of alien species proliferation and its causes make it possible to predict the type of plant community and location where alien species are likely to penetrate, as well as what alien species to watch with caution. A case in point is the ongoing vegetation study at the Kokai river basin in Ibaraki prefecture regarding burr cucumber and giant ragweed (ambrosia trifida) that aims to determine vegetation types that are vulnerable to the proliferation of these invasive alien species. Experiments involving the elimination of alien species and the competition between alien and indigenous species will clarify the competitive situation between the two groups of plants, and will help identify indigenous species vulnerable to impact by invasive alien species. Also, a concern has been raised as to the possible impact on Japan's agriculture and ecosystem by foreign herbicide-resistant weeds that may be imported mingled with grain. Emergence of herbicide-resistant weeds in grain-exporting countries will be compiled into a list for use in risk assessment work in the event of their arrival into Japan.

In an earlier study, we have demonstrated that hybrid individuals of Japanese dandelion and Taraxacum officinale are widespread in Japan. Analysis of germination characteristics and seedling survival of these hybrid dandelions will reveal the physiological and ecological characteristics of those hybrid clones that present a high risk of establishment and proliferation. In addition, research is underway to establish techniques to extract DNA from micro samples, to extract and analyze DNA from herbarium specimens kept in museums and other institutions throughout the country, and to estimate the times and places of occurrence of hybridization.

Efforts are also directed to assessing the growth inhibition activity of invasive alien species and determining the chemical structures of growth inhibiting substances contained in invasive alien species that show high production rates of such substances. In related efforts, growth characteristics of alien species in soils with different chemical properties will be investigated through field studies and indoor culture studies. Also, pilot studies are being carried out in an experimental station on proliferation prevention techniques including use of cover crops.

A list of herbicide-resistant weeds in foreign countries has been prepared, and it will be compared against the status of immigration of conspecific plants into Japan. The plants on such a list are subjected to risk assessment with due attention to their respective ecological characteristics, geological distributions, which kinds are herbicide-resistant, and their modes of growth, so as to assess the new entry into Japan of herbicide-resistant plants.

In addition, new prediction equations have been developed, which are used to predict invasion probability, proliferation radius and proliferation speed of alien species. With respect to natural enemy insects of foreign origin, assessments will be made on the impact on indigenous species from the viewpoints of settling capability, proliferating capability, competition and hybridization, in order to assess the risk to the agricultural ecosystem. Molecular markers and other techniques are used to develop methods for early detection and monitoring of foreign natural enemy insects whose species are not easily identifiable.

Relevant Outcomes to Date

The Rural Landscape Information System (RuLIS) developed by NIAES was used to analyze plant communities having high frequencies of alien plant emergence. The analysis has revealed that alien plants are likely to invade plant communities that have suffered anthropogenic disturbance. Heavy impact on biodiversity was confirmed with respect to burr cucumber which suppresses indigenous species, and the aquatic plants Myriophyllum aquaticum and Elodea nuttallii that suppress endangered species. In addition, a technique has been successfully developed for the specific detection of allelopathy, which has led to the detection of approximately 4,000 alien species. The details and achievements of this project are available at the following website: http://www.naro.affrc.go.jp/archive/niaes/rp/eng/index.html

A method has been developed to estimate the invasion probability and proliferation distance of alien species, which has been successfully used to estimate the invasion probability of apple fire blight. A DNA marker has been developed which permits identification of Torymus sinensis and other alien insects that had not been easily distinguished from the indigenous insects. The distribution of invasive alien species golden mussel (Limnoperna fortunei) in Lake Kasumigaura has been investigated and was found to involve approximately 1/2 of the lakefront.

In order to prepare against the invasion of new alien species, we have constructed the Asian-Pacific Alien Species Database, abbreviated as APASD. For details of this database, please refer to the following website: http://apasd-niaes.dc.affrc.go.jp/ (temporarily closed for maintenance)