Timber, knots and all

Unlike other structural materials, timber production can work in direct harmony with nature, but as a living material it is also uniquely vulnerable.

• Deforestation
  Unregulated and unsustainable deforestation happens around the world, where forest is felled and not replanted, making way for other land use, or simply to harvest the timber. This devastates the ecosystem in pursuit of profit. Despite the industrialised nature of European forestry, it is not deforestation. All major timber producers are FSC/PEFC certified, planting more than they fell. This is sustainable at a basic level, as forest area grows 1–3% per decade (up 9% since 1990). Certification also means sticking to other forest stewardship rules and practices, depending on the location and certifying body.
• Clear cutting
  Although certified sustainable forestry is a vast improvement over the unregulated deforestation which still happens around the world, it still prioritises yield over resilience. Trees of the same age and species are grown and harvested en masse in a process called ‘clear cutting’. As well as devastating habitats during felling, the resulting ecological monoculture is vulnerable to disease and environmental factors.
• Continuous cover
  Trees of mixed ages and species are planted together then selectively felled when they reach maturity. By maintaining forest cover, this process and is more resilient and supportive of biodiversity. It is, however, far more labour intensive and less productive, thereby reducing the amount of carbon sequestration and increasing the operating costs for timber producers, making it uncompetitive. Large timber companies are now exploring forest restructuring to combine elements of continuous cover forestry with clear cutting, to get the best of both.
• Unlogged
  Considered ideal for biodiversity, unlogged forests sequester less carbon because tree growth slows down once the tree reaches maturity. Some species also thrive in forest clearings. Unlogged forests don’t generate much money, which shouldn’t matter but in today’s world a forest may be more resilient if it can pay its way.

Currently mass timber makes up a small proportion of UK construction. We all know that deforestation is a bad thing, so it’s a reasonable concern that greatly increasing our use of mass timber might overstretch and deplete forests.

Thankfully the data tells a different story. At present, Germany and Austria are responsible for over 50% of global mass timber production, yet this utilises just 10% of their sawn softwood output, which in turn is only 10% of their theoretical maximum sustainable output, based on forest area. So by diverting material from other products such as furniture, and by harvesting more from currently underused forests, they could potentially increase mass timber production 100x. On top of that, Germany and Austria account for less than 10% of EU forest area, and many other countries have significant production which could also be scaled up.

Despite the healthy forest cover in continental Europe, the UK is in far worse condition with just 13% forest cover (compared to 37% in France and 47% in Austria) and is one of the most nature-depleted countries on earth. There is sustainable domestic forestry, but it does not produce timber of the grades or quantities required to compete with the imports, which benefit from decades of experience and economies of scale. Huge investment would be required to plant trees, and then we would have to wait decades for them to mature. Climate change further worsens this problem, as high grade softwood grows in cold climates. So in order to restore our forests we should be planting resilient mixed species from more temperate areas such as central France, as opposed to spruce and pine monocultures from Scandinavia.