25 Sep 2022

Blog: Which Woodlands for carbon – A #ScotClimateWeek special

Scotland’s forests and woodlands play a significant role in helping tackle climate change.

Around 7.6 million tonnes of harmful CO2 are soaked up by our forests each year. That’s no mean feat and to put it in context, that’s around 14% of all of Scotland’s gross emissions.

But the question which sometimes pops up is whether some trees are better than others when it comes to soaking up CO2. There’s so many factors involved in answering that question.

However, Forest Research’s experts recently carried out a very comprehensive study into this to shed light on CO2 uptake by different types of woodland. The study is thought to be the most definitive of its kind in the UK and contains a lot of technical detail.

For #ScotCimateWeek we got in touch with Pat Snowdon, Scottish Forestry’s Head of Economics and Woodland Carbon Code, to ask him to explain some of the key questions that have arisen from the report.

pat snowdon

What is the purpose of the report?
It’s widely known that trees are one of nature’s ready-made ways to control the amount of GHGs in our atmosphere. They take CO2 out of the atmosphere as they grow and lock it away as carbon in their stems, branches and roots, and in the soil. But we are often asked “which trees are best at doing this?” There have been different claims about this in the media and elsewhere.

The answer to this question is the subject of a new report by Forest Research which used forest growth models to analyse how much CO2 is removed by different types of woodlands. Twelve different types of woodlands were examined, covering conifers and broadleaved woodlands and areas where trees can naturally re-colonise.

What does the study say?
The key finding is that all types of woodland have important roles to play, although rates of CO2 uptake vary across different species and locations. Good woodland design and management are critical to achieving early CO2 uptake, for example by minimising releases of CO2 from soils and existing vegetation when planting.

Differences between different woodlands are most apparent in the period now up to 2050 when fast-growing conifers can achieve the fastest rates of CO2 uptake. Broadleaf woodlands begin to catch up later, and accumulate a large and permanent on-site store of carbon.

Timber harvesting has an important effect too. Although it removes carbon from woodlands, the resulting wood products can store a lot of carbon and avoid GHG emissions where they substitute for other materials. Such effects can be almost as important as CO2 uptake within woodlands, albeit some time into the future when timber extraction takes place.

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Any cautions around the study?
Care is needed when interpreting the findings. Simple comparisons across the different woodland options can be misleading. Different types of woodland will suit different locations across the UK, and some are not suited in certain places. It’s important to plant ‘the right tree in the right place’ rather than assume that particular types of woodlands are always best for tackling climate change.

How does this link to Scotland’s emissions reduction targets?
All woodland creation is recorded in the Scotland (and UK) GHG Inventory. This inventory records GHG emissions across the economy and allows government to see how well the country is moving towards its climate change targets. By removing CO2 from the atmosphere, woodlands help to reduce overall emissions.

The types of woodland that we plant in future will affect the rate at which our forests soak up CO2 and, therefore, what forestry can contribute to GHG targets. Scottish Forestry is using the findings to help plan forestry’s contribution to the next Scotland Climate Change Plan, due in late 2023.

How can land managers use the data in the report – both in the short and longer term?
The report gives reliable information to help all those involved in planning and planting woodlands. The data in the report will help help farmers and land managers to see how much CO2 uptake they can achieve by planting different tree species at different sites.

This will allow them to work out how best to manage their land in a climate-friendly way. For example, farmers may want to register a woodland creation project under the Woodland Carbon Code to generate carbon credits to use either against their own carbon footprint or to sell to others.

Strathspey overview FLS

The report says that conifers are better for soaking up carbon – does that mean we need to plant much more conifers?
The report is more nuanced in its findings. Conifers are a good approach in the short-term on the right site and, where harvested in future, will offer benefits through wood products. However, broadleaves that are not harvested commercially accumulate a vital and permanent store of carbon on site.

Net Zero is a goal that we will need to continue beyond 2050. A diverse forest estate will be needed to maintain that into the long term and it is important to remember that trees also provide many other benefits.

While CO2 uptake is the focus of this report, deciding which types of woodlands are best in different situations depends on other factors too.

Do we think the report might polarise opinion on conifers vs broadleaves?
I hope not. We want it to strengthen understanding of the contributions that different parts of the forest sector can play in helping to tackle our climate change targets.

Forestry has long-term objectives and Scotland’s Forestry Strategy sets a vision for 2070.

The Forest Research study is also clear that both conifers and broadleaved woodlands, and natural re-colonisation, all have important roles.


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