A Threat to Thatch
Perhaps because they're so popular with illustrators of children's books, homes with thatched roofs occupy a special place in the hearts of people who wouldn't dream of living in one. These shaggy shelters look as if they should be occupied by elves or gnomes--maybe with a plastic stockbroker decorating the lawn.
The gnomes may soon be homeless. According to the specialized journal Aquatic Botany, something's gone wrong with these roofs. Reed thatchwork that once lasted (with occasional repairs) for 50 to 80 years now decays and loses its weatherproofing capability in 4 to 10 years.
Because thatch is still a popular roofing material in many places, this isn't a trivial problem. According to researcher S.M. Haslam, Britain alone imported more than 8 thousand tons of reeds in 1985--even though most roofing thatch in Britain is home grown. The imported reeds help make up for the loss of wheat straw that provided thatch for many English homes before about 1960, when farmers began growing short-stemmed wheat--no match for six-foot reeds.
Complaints about fast-failing thatched roofs began appearing in the early 1970s, and by the early 1980s the situation was starting to look serious. Instead of shedding rain, the thick butt-ends of the reeds--the only portion actually exposed to weather in the thickly layered construction--were absorbing moisture. The damp reeds were attacked by fungus, and ultraviolet light further weakened them. Wear that once took half a century now came in half a decade.
Exactly why this plague of short-lived thatch has struck isn't known, but researchers say it's not shoddy workmanship or even acid rain falling on English and European roofs. The problem seems to lie in the reeds themselves; they're softer than they once were.
People have made use of reeds for thousands of years, and the relationship has been a pretty comfortable one. Growing naturally along calm watersides, reed beds stabilized shores, purified water, harbored and fed fish, waterfowl, and mammals useful to humans. Harvested reeds provided shelter, and the harvesting seemed to do no damage to reed beds.
Harvesting even helped the reeds in some ways. Dead stalks did not accumulate, a process that eventually would build up too much soil in the beds--in many places, reed marshes would become dry ground without human intervention. People who tended reed beds often burned them after harvest, further reducing the chance for dead stalks to build up and also liberating nutrients helpful to the next year's growth.
Somehow, in the last few decades, this relationship has changed. Reed beds are retreating all over Europe, but not from any single cause. Dredge and fill operations have wiped out some; an increase in waves caused by high-powered boats have chewed away others. Some apparently even have been overgrazed by swans and muskrats.
Though these things reduce the number of reeds, they shouldn't reduce their quality. It's still a matter of speculation, but the researchers suspect the chief cause of the quick-rotting roofs is an interplay of factors operating differently in different reed beds.
Fertilizer washed from farmers' fields is one suspect. Experiments with laboratory-grown reeds show the shoots are softer when the plants have plenty of nitrogen and phosphorus. Harvesting methods are another possibility; as the demand for thatching material increased, more reeds were harvested when they were younger, and perhaps softer. The overall environment in which the beds live has changed markedly, as odd chemicals pervade the waterways and different land management practices affect the surrounding terrain.
The awful suspicion that Haslam and her colleagues harbor is that the complex of changes has encouraged the predominance of softer reeds. Many adaptable species have a great breadth of expression within their genetic makeup, and their offspring show great diversity--some of them will do well if the world changes. Once the world was a suitable place for stiff reeds; now, though some tough specimens still thrive, their habitat favors softer plants (though the apparent flimsiness may simply be, from the plants' point of view, a byproduct of more important adaptive features).
As all scientists are fond of saying, much research remains to be done. And, while thatched roofs are about as common as fanged Ptarmigan in Alaska, the plight of thatched roofs is not simply a tale of passing interest to northerners. It's a reminder that the world has many surprises left for humankind, even in aspects that we've taken for granted over centuries untold.
