Plant hunters' legacy help Japan's threatened species

Magnolia stellata (Image: John Anderson) When Japan opened its borders in 1854, plant hunters flocked there in search of exotic species

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The British tradition of collecting plants from all four corners of the world means the UK is now home to many Japanese species which are under threat in their native land, a study reports.

Botanic Gardens Conservation International found more than 350 such species in UK gardens and collections.

They also counted 106 vascular plant species in UK collections that were not present in Japanese ones.

They hope the findings will help protect potentially vital specimens.

The report found two species - a shrub, Flemingia strobilifera, and a fern, Hypolepis tenuifloa - growing in the UK despite being deemed locally extinct in their Japanese homeland.

"There was a period of time where it was very much the thing to do and go out and collect plant material, and Britain was probably at the lead of it," explained Suzanne Sharrock, director of global programmes for Botanic Gardens Conservation International (BGCI).

"It is fair to say that we have always had a tradition of gardening and an interest in plants.

"And - certainly among the upper classes - they wanted new and different plants that no-one else had. That was probably the spur behind it."

Biological bounty

Japan became a magnet for plant-hunters in 1854 when its rulers ended their self-imposed 200-year trade exile, after accepting it would not result in the invasion of the nation.

Acer pycnanthum (Image: Westonbirt Arboretum) Maples' autumnal colours made the genus popular with western gardeners

The archipelago provided a number of biomes, from sub-tropical to sub-Arctic, which contained a rich array of botanical delights for those in search of new and commercially important species.

It is considered one of the Asia-Pacific region's biological hotspot, with an estimated 7,000 native species of vascular plants, of which 40% are endemic to the islands.

With such biological riches waiting to be harvested, Japan attracted botanists from countries across Europe, including the Netherlands, France and Britain.

In their numbers were the likes of Ernest H Wilson, a prolific collector credited with introducing about 2,000 species from Asia to the West, including the kiwi fruit.

Even today, species from Japan continue to attract the attention of western horticulturists, from maples and their autumnal display to the flowers of azaleas that signal the arrival of spring.

Dr Sharrock acknowledged the irony of finding that the plants' popularity in the West have played a part in their decline within their native habitat, pushing some species closer to extinction.

"There is a continuing push to look for new things, and some of the species that are now under threat are definitely under threat because they have been overcollected as a result of their popularity," she told BBC News.

Red alert

The report identifies 50 Japanese gardens in the UK - including botanic gardens, arboreta and collections of Japanese plants - that collectively contain 356 species featured on the Red List of Japanese vascular plants (species with tissue to transport water and nutrients through the plant).

The species were identified through databases such as the BGCI's PlantSearch and the UK Tree Register.

They were then cross-referenced against the 2007 Japanese Red List to see which of the species were deemed to be under threat.

Dr Sharrock said that a number of species on the threatened list were relatively common sights in gardens and collections across the UK, including:

  • Magnolia stellata (often referred to as the star magnolia) - its flowers, which consist of up to 30 petals, open before its leaves. The first specimen was introduced to UK gardens in the late 1880s, yet within Japan it is only found in the wild and its habitat is under threat. As it is naturally only found in Japan, it is deemed to be globally endangered in the wild.
  • Acer pycnanthum - a rare maple, which is only found in Japan. There are an estimated 1,000 mature individuals remaining in the wild, which are distributed across approximately 60 locations. The expansion of commercial forestry is one of the main threats facing the species.

Dr Sharrock explained that in order to build on the report's findings, the BGCI would share the results with Japanese scientists.

"They feel the next step is to check the identification of these species to make sure they are correctly identified," she said. "Then it will be a case of looking at the size of the collection to see the amount of genetic diversity that is represented.

"If it is one plant growing in one place then, in terms of using it for conservation purposes, the scope is limited. But if it is a reasonable size collection or if it is found in more than one location, then it could form the basis of a conservation collection."

While the report focused on Japanese flora found in UK gardens, she added that the model could be applied to other nations as well.

"I think it is the same for all countries. Regardless of its state of development, every country in the world is grappling with extinction crises to their native plants," she observed.

"A developed country may have more resources to deal with the issue, but they also have a lot of competing demands."

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