Larch trees were introduced to Britain from eastern Europe in the 17th century for their ornamental value in gardens — and the larch is indeed a pretty tree.

A conifer with short, needle-like leaves that turn color in autumn and fall like golden rain, the larch’s new foliage sprouts afresh in spring in small, soft, bright-green bunches on its pale-brown twigs.

Larches grow straight and tall, and usually at twice the speed of British hardwood deciduous trees such as oaks or beeches. As a result, larches were later often planted as “nurse trees” in commercial woodlands to encourage slower-growing hardwoods to rise up straight as they competed for light, while the bigger larches also helped shield them from the wind. Additionally — unlike conifers such as cedars or cypresses — the larches did not create dense shadows that restrict growth on the forest floor.

Besides all those benefits, harvested larch timber was also found to be not only straight but robust and able to endure changes from wet to dry without too much warping. These qualities made it an excellent choice for use in construction and for pit props in coal mines.

When Japan finally opened its doors to the rest of the world after the Meiji Restoration of 1867, Western plant-hunters spread out throughout the country in quest of hitherto unknown and potentially valuable species.

At that time, some Westerners, mainly Europeans, were already aware of Japan’s richly diverse floral wealth through the writings, illustrations and collections of Engelbert Kaempfer, a German physician and botanist who arrived here in 1691 as a surgeon aboard a Dutch ship. He stayed for two years at Dejima, an island off Nagasaki constructed in 1634 which was the Dutch East India Company’s base in Japan.

Although foreigners were confined by law to this man-made settlement, due to his good manners, education and diplomacy, Kaempfer was twice permitted to make the long journey to the Tokugawa Shogunate’s capital of Edo (present-day Tokyo).

One of the many Japanese plants introduced to Britain in the late 19th century was the Japanese larch (Larix kaempferi), or karamatsu in Japanese. This timber was used to make pit props for the nation’s then-thriving coal-mining industry, and when I was a boy growing up in South Wales plantations of these trees were a common sight.

When I revisited South Wales in the 1980s and became inspired by the massive efforts being made there — and especially in the Afan Valley — to restore forests to areas that I remembered as having been devastated by the coal-mining industry or razed to short grass by sheep, I made note of the dense plantations of larches and felt they badly needed thinning and trimming.

Over the years, I became friends with rangers and forestry workers in Wales, and eventually our little woodland trust here outside Kurohime in the Nagano Prefecture hills became “twinned” as a sister woodland with the Afan Argoed Forest Park.

On one of my annual visits, I told the park’s chief ranger, my good friend Richard Wagstaff, that I thought it would be best to thin out the densely crowded larch trees and mix in some indigenous hardwoods. We have done such experiments in our own Nagano woodland, and found that a mix of trees not only improved biodiversity and wildlife numbers, but also encouraged the larches into vigorous growth that yielded better, bigger timber.

Two years ago, a senior forestry official in Wales told me that it had become official government policy there to gradually thin dense conifer plantations and mix in hardwoods, and that they would be doing that in the Afan Argoed Forest Park. As a result, there was a lot of planning and preparation going on to make good use of the extracted larch timber.

The better-quality trees would be milled and marketed as lumber, and the rest sent to a new biomass plant that could turn the wood into energy. It seemed ironic at the time that these larches — planted mostly to support a coal-mining industry that’s now been felled by a government ax — should themselves be about to be axed to create energy, instead of them helping in the mining of long-buried fossilized forests.

In 2009 though, a fungal pathogen with the scientific name of Phytophthora ramorum was found in various trees and plants in the counties of Devon, Cornwall and Somerset in southwestern England. The spores of this awful disease are carried by moist wind and mist, or on tires, shoes and such — and it spreads very quickly indeed.

Earlier this year I was informed that many trails in the Afan Argoed Forest Park were being closed off because the pathogen had spread to nearby South Wales to the north. There, it was already starting to kill off Japanese larches in the park, which it does from the treetops downward, turning the foliage brown as if autumn has come early.

This nasty fungus can affect a whole range of plants and trees, killing off leaves and causing bleeding cankers on trunks. In the Welsh park, which is famous for its mountain-bike and hiking trails, visitors are co-operating by scrubbing and washing off tires, shoes and boots and disinfecting them before leaving.

Sadly though, it seems that the only way to really try to stop the spread of the disease is to fell the larch plantations. In that part of Wales, though, there is only one local mill that can handle the cut larch logs with adequate biosecurity to ensure the spores are destroyed while preserving the quality logs as lumber and sending the rest to be burned in the biomass-energy plant.

Nobody wants to just pile up the logs and let them rot, but what to do with such a glut? For one thing, the price of larch lumber will be depressed. In Wales, everybody who is aware of this problem — whether mountain-bikers, hikers, birdwatchers, nature lovers, foresters or the general public — is deeply worried and concerned.

Visiting recently, my heart went out to them. They had been just about to embark on a wise and adventurous forestry, wildlife and water-conservation project with their planned experiments to mix the woods. People were looking forward to it. But now? Wham!

Suddenly those plans have had to be canceled and there is a whole new Pandora’s box of problems to consider. Do you spray the cleared areas to try to kill off the Phytophthora ramorum spores? What would that do to other wildlife? Do you attempt to replant? Do you let the woodlands regrow and just wait and see?

At least in Wales, people who are either directly involved or otherwise concerned are seriously putting their heads together. They are thinking and acting. I am terribly worried about what could happen if this disease spreads to Japan.

Over the years, I have despaired and nagged whoever I could in this country over the lack of action in tackling the dead and dying pines. Although pines are treated with great care in public parks, where people admire the trees every day, elsewhere — from Hokkaido to Okinawa — dead pines in their millions just stand there until they fall over.

With a fatal disease similar to the larch pathogen already afflicting Japanese oaks, I can’t help being pessimistic and expect the larch disease to also reach these shores. When it does, it will kill off huge areas of trees — and if those larches are left to stand dead and dry, like the pines and the oaks, there will be a terrible potential for disastrous forest fires.

Instead, when the trees start to die, there must be staff out there to make decisions and skilled, dedicated workers to cut and handle the felled timber. Japan has (or used to have) the expertise to handle such a crisis, but at the moment, I have no confidence in either the government or the private sector.

If it happens in our woods, as soon as the disease is noted and identified we will cut and convert the lumber to charcoal. I doubt if anybody elsewhere in Japan will bother. Old Engelbert Kaempfer would turn in his grave.

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