Environmental Engineering Reference
In-Depth Information
I find such a high figure extremely difficult to justify. Swansea is, almost everyone agrees, excep-
tional. Few other authorities impose planning requirements for knotweed, because it is not a problem to
them. CABI offers two reasons to justify assuming the rest of the country is like Swansea. The first is
that “much of the country will be behind Swansea in Japanese knotweed management.” In other words,
other places may not be spending that kind of money, but they should—and probably will one day. The
second is that, as Shaw put it to me, Swansea “was the only place in the country that had any figures at
all that could be scrutinized.” As fuzzy as this line of reasoning is, it is what CABI's figures are based
on, and those at other professional bodies I spoke with seem willing to accept it.
It also justifies Shaw's work developing a “biocontrol” for the weed. His CABI headquarters down
a leafy and JK-free lane south of London is working on deploying a Japanese louse called Aphalara it-
adori that he collected on Japanese mountains and nurtured in his labs. But after three years of trials at
eight sites, including one near Swansea, he had to report that “each time we have had a weather disas-
ter—cold nights, late springs, or wet summers—the louse always died.” He was thinking of going back
to Japan to get a new stock of lice or pushing the government to allow bigger field trials.
My skepticism about CABI's calculations does not mean there is no issue. There is. The locals hate
Japanese knotweed. It can blight their lives. But not because of any damage it does to their homes or
gardens. That is minimal. The problem, everyone in Swansea I spoke with said, was the panic it creates
among banks and others who finance loans to buy houses. If there is a hint of knotweed, some will not
lend at all. Japanese knotweed was a problem weed that needed no more than careful handling until five
years ago when media stories started to appear. Then it became “the scourge that could sink your house
sale,” according to the Guardian . “Britain is in the grip of an alien invasion,” said the Daily Mail . A
“race of female clones . . . with giant root systems that burrow down nine feet and towering bamboo-like
stems that grow four inches a day” was spreading across the land. 8
“Mortgage lenders started to go spare. Some won't lend at all now if there is knotweed on the prop-
erty,” Hathaway told me. “It's ridiculous. The houses are as valuable as they ever were.” At the very
worst, if the weed was pushing its way into the living room, it would cost a few thousand pounds to get
rid of it. That is tiny compared to the value of the house.
Many independent observers take a similar view. John Bailey at Leicester University, who has stud-
ied the weed for thirty years, says “the hysteria about Japanese knotweed is absurd, and is distressing
lots of people.” The weed will, he agrees, grow fast after being moved in soil, as happened in Swansea
forty years ago and also more recently during the Olympic construction activities in East London. But it
does not spread like wildfire. It will invade cracks but does not push through solid concrete. It is some-
times a problem weed, for sure. But it is not a $250-million-a-year problem. 9
Nor is it an environmental threat. I asked Hathaway if JK had spread into the countryside around
Swansea. He laughed at the idea. “Not at all,” he says. The entire infestation in the city and surrounding
area, which includes the scenic Gower Peninsula, is 250 acres, mostly on public wasteland. The biggest
single patch I saw covered five acres on a hillside overlooking the railway. Jim Dickson, a botanist at
Glasgow University, says JK usually stays in urban environments, where the disturbed soils it likes are
mostly found. In cities, much wildlife rather likes it. Otters, for instance, are returning to cleaned-up
rivers across the country. In Sheffield, their favorite place to hide out is beneath the protective foliage
of dense stands of Japanese knotweed along the bank of the River Don. Knotweed has other uses too. It
is a valuable source of nectar for insects, including honeybees. The Japanese revere its medicinal prop-
erties as a source of the polyphenol resveratrol. Richard Mabey, the naturalist and national champion
of weeds, says the young shoots make a nice vegetable. In the United States, Japanese migrants eat it
cooked, like spinach. 10 If the rest of us learned to stop fearing it, maybe we could do the same.
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