Free tree? Why we can’t plant our ways out of a climate crisis

Can the solution to climate change be found in trees? This is the question that many people in Cardiff and Ceredigion are asking after the Welsh government announced this week. every household will be offered a free native species tree – which people can nurture in their own gardens or have added to woodland on their behalf.

Such planting initiatives have become increasingly central to the world’s efforts to combat our environmental emergency, with oaks and spruces removing carbon dioxide from the atmosphere and storing it in vegetation and the soil.

Councils in Glasgow, the host city for last month’s COP26 climate talksIn the next decade, he promised to plant 18,000,000 trees. The woody plants accounted for a quarter of the one. Boris Johnson’s key mantras ahead of the summit – “coal, cars, cash and trees” (a slogan that even made it into his former aide Allegra Stratton’s tearful doorstep resignation speech this week).

The Government pledged to plant 11 million trees in England between 2017-2022. And last year, the World Economic Forum launched its One Trillion Trees Initiative to conserve, restore and grow that number by 2030, though critics have described it as “a form of magical thinking”.

Dominick Spracklen, a professor of biosphere–atmosphere interactions at Leeds University, believes the discussion is a perennial that will endure, but which often ends up lacking nuance.

“There is no one silver bullet to solve climate change,” he tells i. “Planting trees without doing anything else will be a complete disaster.

“There’s nothing wrong with announcing a big tree-planting effort. We know that the UK needs to increase its woodland tree cover in order to reach net zero. We all know that we must do it to restore biodiversity. But we need to remember that we need to protect our ancient woodlands at the same time.”

This latter option may seem less attractive to politicians than the creation of new forests. Massive old trees are much more carbon-rich than new saplings. One tree with 100cm diameter can store as much as three tonnes of carbon – more than 100 times as much as a younger tree with a 10cm diameter.

Our ancient woodlands – areas continuously wooded for centuries, perhaps even since the last ice age – cover only 2.5 per cent of the UK, but are exceptional in terms of biodiversity value. While they are under threat from the likes of nitrogen pollution, roads and railways and invasive species such as rhododendron, the Woodland Trust has said the protection they are afforded “is currently too weak” and their role attracts too little attention from policy makers.

A new analysis has been completed for the State of the UK’s Woods and Trees 2021 reportIt was found that, although they only account for a quarter of British woodlands (about 25%), they hold more than a third the total carbon.

Spracklen believes that creating conditions for forests to naturally reshape themselves is the best choice. But when it comes to planting, our motto must be “right tree, right place”. He favors native species and warns against monocultures which are not resistant to disease and climate change.

In the 1970s and 80s, the Flow Country blanket bog in North Scotland was planted with fast-growing conifers. This caused the peatlands to lose large amounts of carbon.

That is a disaster we have learnt from, but today, says Spracklen, “across the UK, you’ll see these plastic tubes go up and then next year they’re all blown over and that’s not going to create a woodland. That’s just creating a load of plastic mess.”

Experts believe we should think beyond the (timber box). Hemp can capture atmospheric carbon much more effectively than forests, says Dr Darshil Shah, a senior researcher at the University of Cambridge’s Centre for Natural Material Innovation.

“Because hemp can be grown in such large densities and because it grows rapidly, it is able to capture up to two times more carbon,” he says.

Hemp, a type of cannabis plant that can be grown in the UK, can also be used to produce carbon-negative biomaterials such as insulation for homes and interior doors panels for cars.

“The key with many of these plant-based materials is you want to ensure that the carbon is locked in the structure for as long as possible rather than being released back into the environment [through rotting or burning], therefore using them in long life-span applications is critical,” says Shah.

We must look at the whole picture when it comes to nature. The planting of trees is the easy, headline-grabbing, and cheap part. Spracklen says that the local community must be involved right from the beginning. They are the ones who will need to care for the trees, protect them from pests, and other threats for generations. If the new forests are to have any lasting impact on our carbon problems, Spracklen says.

Of course, trees offer us so much more than natural “carbon sinks” – including recreation, quality of life, urban shading and protection of wildlife. However, their grandeur must not prevent us from seeing the wood in the trees, especially when greenhouse gases are still wreaking havoc around the world and deforestation is still rampant. You can’t just plant your way to a climate crisis.