2012-08-30

Building materials: Wooden skyscrapers

WHEN life hands you lemons, goes the old saw, make lemonade. But what if life should hand you 18m hectares (44m acres) of dead trees? That is the problem faced by the province of British Columbia in Canada, which could lose over half its pine trees to the depredations of the fearsome mountain pine beetle. The beetle, no bigger than a grain of rice, is native to the forests of Western North America, where it kills trees by releasing a blue stain fungus that prevents the flow of water and nutrients. While the insect was historically kept in check by spells of cold weather, years of mild winters have unleashed an outbreak whose spread and severity is unlike anything seen previously.

As a result, the province is peppered with billions of dead, grey trees. If they are simply left standing, they will eventually either decay or burn in forest fires. In either case, they will release the carbon dioxide they stored while growing, swelling Canada's total carbon footprint from 2000 to 2020 by 2%.

So, to deal with the problem, in 2009 British Columbia's parliament passed a Wood First Act that requires wood to be considered as the primary construction material in all new buildings erected with public money. The striking Richmond Olympic Oval for example, used for ice-skating events during the 2010 Vancouver Winter Olympics, features 1m board feet (2,360 cubic metres) of beetle-affected wood. But harvesting trees for traditional purposes will make barely a dent in the massive wood pile, especially while one of Canada's main outlets for wood, the American residential-housing market, remains depressed.