Species diversity key for climate resilience

10 June 2022

We must widen our timber diet to ensure future supply, writes Dan Ridley-Ellis, head of the Centre for Wood Science and Technology at Edinburgh Napier University

As innovation in construction timber use intensifies, it’s easy to overlook changes going on with the wood resource itself.

Recent challenges with wood supply are driven by relatively short-term factors, but they sit on top of longer-term trends that point in the same direction: if we do not prepare to widen our wood diet, our growing appetite will not be met.

One reason for increasing the use of wood in construction is to reduce the built environment’s huge climate impact. What is often left unsaid is that the built environment is also vulnerable to effects of climate change, including over-heating, storms, floods and landscape scale fires.

The way we build and operate buildings must adapt to trends already locked in. Fortunately we do have wood, the new superhero material, but like all superheroes its weakness is part of its origin story.

The theme of the April Institute of Chartered Foresters conference was climate smart forestry. It asked how forests can be managed to help them adapt to potentially disastrous effects of climate change.

The best way forward is not clear, but it certainly is not business as usual. Forests will need to diversify in species and management for resilience. Even when this does not happen, the trees themselves are already responding and our familiar, commodity commercial timbers will be changing.

In September, the Northern European Network for Wood Science and Engineering will hold its conference in Goettingen, Germany. The theme will be “tackling scarcity of resources in the wood industry under changing European forestry conditions”.

One challenge is that the process of establishing grading possibilities is very costly and often disproportionate to the size of the resource. How can we diversify in a system originally intended to encourage uniformity and simplicity of material specification?

But what does diversity mean anyway? Species is certainly important to foresters, but as far as wood properties go, there’s often more variation within single species, than between averages of two species.

While species is undoubtingly important to strength grading, it is often a clumsy fi t for timber engineering. On one hand, we have fuzzy distinctions for naturally hybridising species like larch, on the other, numerous important distinctions below species level such as subspecies, cultivars, seed provenances and clones.

The way forward probably involves more species combinations, attempting to maintain simplicity for the end user. Work is already under way, with a new grading combination of UK and Irish-growing larch and Douglas-fi r being approved, rendering the otherwise comprehensive open access paper “Strength grading of timber in the UK and Ireland in 2021” incomplete a few days before it was published (https://doi.org/10.1080/204 26445.2022.2050549).

That said, the bigger need is to be able to retain and adapt buildings we have, or at least reuse some of the structural timber.

The InFutUReWood project (www.infuturewood.info) was working on this question, and testing in Ireland, Spain and Slovenia showed good potential for reuse, providing the strength grading problem can be solved.

The good news is that it is almost the same problem as the species diversity one.

Dan Ridley-Ellis