Comparison of invasive alien species in Japan and South-Eastern Australia
In spite of different histories of human occupation and land use, Japan and South-Eastern Australia host many of the same exotic plant species. South-Eastern Australia and Japan are spread over similar latitudes and the range of climates on the east coast of Australia are similar to those in Japan.
Prior to 1788, Australia had been occupied for at least 60,000 years by semi-nomadic hunter-gatherers. There was a huge flux of exotic plants into Australia in the 19th and early 20th centuries. Agricultural enterprises have been principally sheep and cattle grazing and dry-land wheat farming, although a greater range of agricultural and horticultural activities has been taking place in the last 30 years.
In Japan, agriculture has been practiced for more than 2500 years. Paddy rice was introduced around 300 years B. C. (Jomon period), but upland farming with Echinochloa spp., Setaria spp., Fagopyrum spp. and tropical Japonica spp. rice was conducted even earlier. Although there were contacts with Europe in the 16th century, Japan had remained generally isolated from external influences (by sakoku, the national seclusion), apart from neighboring Korea and China until 1853. It was therefore after this date that exotic plants have been introduced to Japan. From 1910 to 1945, Korea was a Japanese colony, and 2 million Koreans migrated to Japan in 1945, as well as Chinese in smaller numbers. Most of the naturalized plants in Japan arrived after the Second World War. The USA occupied Japan from 1945 to 1952, and it is suggested that many weeds arrived as contaminants of wheat and soybean imported from North America to alleviate food shortages after World War II.
In spite of these contrasting histories and agricultural practices, many invasive plants are common to both countries. The total number of alien plants is similar in Japan and South-Eastern Australia, although the time of arrival of most species is more recent in Japan. Their arrival coincides with a period of rapid economic growth; with the construction of highways and the extension of the railway system providing corridors of disturbance for invasive species. Most of these invasive species originated from either the broad region of Europe/Mediterranean/Eurasia or the Americas. Invasive alien plants common to Japan and South-Eastern Australia include for instance Alternanthera philoxeroides (Amaranthaceae, EPPO Alert List), Ambrosia artemisiifolia (Asteraceae, EPPO List of IAP), Helianthus tuberosus (Asteraceae, EPPO List of IAP), Pistia stratiotes (Araceae, EPPO Alert List).
The comparison of the exotic floras of the 2 countries allows potential invaders to be highlighted. For instance, the following species are considered to be widespread invasive alien plants of recent arrival in Japan, but have not been recorded as naturalized in Australia: Ambrosia trifida (Asteraceae), Bidens frondosa (Asteraceae), Erechtites hieracifolia (Asteraceae), Erigeron annuus (Asteraceae), Galinsoga quadriradiata (Asteraceae), Rudbeckia laciniata (Asteraceae), Solidago gigantea var. leiophylla (Asteraceae), Barbarea vulgaris (Brassicaceae), Ipomoea coccinea (Convolvulaceae), Sicyos angulatus (Cucurbitaceae, EPPO List of IAP), Geranium carolinianum (Geraniaceae), Ammannia coccinea (Lythraceae), Lindernia dubia (Linderniaceae), Solanum carolinense (Solanaceae).
Sources
Auld B, Morita H, Nishida T, Ito M, Michael P (2003) Shared exotica: plant invasions of Japan and south eastern Australia. Cunninghamia 8, 147-152.