Farm Forestry New ZealandWooden skyscrapers are wonderful, but...
Wink Sutton, New Zealand Tree Grower May 2012.
Google the ‘the world’s tallest building’ and responses include proposals for a 16 to 17 storey building in Norway and for the Creative Renewable Energy and Efficiency group’s plan for a 30 storey building in Austria. Google ‘Vancouver wooden skyscraper’ and the response includes architect Michael Green’s proposal for a 30 storey wooden skyscraper in Vancouver, British Columbia.
As wood suppliers we should welcome proposals that finally recognise the major environmental advantages of wood, such as its low energy requirements, sustainability, carbon sequestration and earthquake benefits. As many of us have advocated for years for the environmental advantages of using wood we must ask why have wood’s advantages taken so long to be accepted?
The promoters of wooden structures are architects and engineers, professions that have little or no understanding of forestry. If there is a move to build large wooden structures we are looking at a quantum increase in wood demand. We would almost certainly see a reversal of the long-term decline in per capita consumption of industrial wood.
The first record of global wood consumption was in 1920. Since 1920 the wood harvest has doubled, but over that same period the global population has increased almost four-fold, so the per capita consumption has almost halved in the last 90 years.
Several projections of the future global wood supply suggest that the global wood harvest could increase slightly over the next 20 years. However, the forest industry could not supply the quantum increase in wood demand that will almost certainly result if there is a trend towards large wooden buildings. Other than those just grown on short rotations for pulping or reconstituted wood products, trees require at least two decades before they are large enough for conversion.
Almost all the trees that will be harvested in the next 20 years are already growing which is why future wood harvests can be so confidently predicted. Even if there is a large increase in the establishment of plantations these will not be available for harvest for at least the next 20 years.
Adding to the world problems is that a significant increase in plantations will require a massive investment as tree growing is the most capital intensive industry there is. Governments have no interest in long-term investments such as plantation establishment. The private sector tends to buy plantations which already exist rather than invest in the creation of new plantations. In contrast, the increased production of steel and cement requires less capital and more importantly only one to four years before production can start.
Wooden skyscrapers are a wonderful development, but more consideration should be given to where the required wood might come from.
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