The amount of carbon dioxide captured by the UK’s forests has fallen by millions of tonnes and will remain at historically low rates for over a decade, because of a failure to quickly replace old forest stocks.
Official data shows the amount of CO2 absorbed annually by trees in the UK peaked at just under 20m tonnes in 2009, but has fallen every year since. Millions of mature conifers have been felled but not replaced, reducing the carbon they capture and store.
Official projections, which are based on the forestry stocks and policies in place in 2019, forecast the carbon they absorb will fall by 25% to 15m tonnes of carbon dioxide equivalent (MtCO2e) a year by 2025. In the absence of any further forests being planted, that could fall by half by 2038 to 10 MtC02e a year, the forecasts show.
The UK has committed to planting 30,000 hectares (74,131 acres) of new trees annually by 2025 to replace older forests that have been harvested and to increase the UK’s overall tree cover. In Scotland, after falling sharply planting rates have risen recently to 11,000 hectares a year and are helping arrest that decline, but have barely risen in the rest of the UK.
Forestry and climate experts say it could take well over a decade before the amounts of CO2 these new forests will capture begins to climb back towards the levels of carbon stored by the UK’s forests in the 1990 and 2000s.
They say that makes it imperative ministers meet their promises to rapidly increase forest and woodland cover, and protect the funding needed, to make sure the UK can hit its ambitious promises to reach net zero by 2050.
The UK’s independent adviser on tackling the climate emergency, the Climate Change Committee, said this month that woodland strategies were “significantly off track”, adding to its warnings Britain was at real risk of missing its climate targets.
It said the British government had to urgently increase new planting by 4,000 hectares a year to meet its 2025 target, and urged ministers in all four UK governments to give “further clarity” on meeting the next targets to plant 40,000 hectares by 2030 and 50,000 hectares by 2035.
The Wildlife Trusts said government planners also had to pay far greater attention to the increased risks of forest fires for the UK, which could consume large areas of forestry and woodland as droughts increased through climate heating.
Others say a changing climate greatly increases the risks of violent storms felling millions of trees, as storm Arwen did last November, and also increases the threat of diseases and parasites fatal to trees – which will also cut the UK’s total forest stock.
Kathryn Brown, director of climate action for the Wildlife Trusts, said: “We shouldn’t forget that trees are dynamic, living things. It takes an individual tree a few decades to start absorbing carbon at a high rate even under ideal conditions for growth. It is therefore especially concerning that planting rates are still not as high as we would want to see right now.
“What is also concerning is that the most recent UK climate change risk assessment projected a doubling of wildfire risk by 2050. This scale of change does not appear to be included in the government’s woodland carbon projections; if it is not there, it should be”.
Pat Snowdon, head of economics and Woodland Carbon Code with Scottish Forestry, a government agency previously part of the Forestry Commission, said the peak in sequestration and the subsequent fall was owing to a surge in commercial forestry planting in the 1970s and 1980s.
Those trees, such as sitka spruce and pine, had matured and were being harvested, but had not yet been fully replaced. The latest tree-planting targets and any plantations that had been approved and funded since 2019 were not factored into the official Forestry Statistics 2021 projections, he added.
“A large area of new woodland was created across the UK in the latter half of the 20th century. Some of this woodland is managed through a sustainable cycle of felling and restocking – felled woodlands must be replanted under law – which results in peaks and troughs in the amount of CO2 that it removes from the atmosphere.
“However, as growth of young trees accelerates in the coming decades, CO2 removals will increase again. Significant increases in new planting in recent years will also contribute to rising levels of CO2 removals in future, supported through actions across the four administrations in the UK.”
