Using forests to fight global warming

The cost of leveraging nature’s precious trees to help buffer the planet from global warming could amount to nearly US$400 billion by mid-century, according to an analysis published in the journal Nature Communications.

With this investment, the study estimates, global forests could capture around 6000 million tonnes of carbon dioxide (CO₂) emissions each year over the next three decades – equating to around a tenth of that needed across all sectors to limit warming to 1.5 degrees Celsius.

The study confirmed the most important target is stopping deforestation in tropical forests, which would account for a third to a half of total mitigations. This includes Sub Saharan Africa, South America and Southeast Asia.

Other regions would benefit most from better forest management, replanting and harvest rotation. Reforestation could sequester up to 2600 million tonnes.

“Our findings confirm a critical role for protecting, managing and restoring forests in mitigating global climate change,” says lead author Kemen Austin from RTI International, a non-profit research organisation in the US.

“Avoided tropical deforestation is one of the most important levers for achieving these targets,” she adds. “Mitigation from improved forest management is another important tool, especially in the temperate and boreal regions.”

The analysis also revealed that the costs accelerate quickly. While it would take just $2 billion to reduce CO₂ emissions by 600 million tonnes, this would escalate to $393 billion for 6000 million tonnes (six gigatonnes) by 2055.

“We find that mitigation in the forest sector will not be consistently low-cost, as has been assumed across previous research efforts,” Austin explains. “As we mitigate more and more, will have to pay higher and higher costs to achieve each additional unit of mitigation.”

The importance of forests is not trivial. Added to their carbon sequestration potential, Austin notes other values include protection of biodiversity resources, ecosystem services and livelihoods.

Her team calculated the global costs of reducing greenhouse gas emissions across 16 regions by protecting, managing, restoring and planting forests using the Global Timber Model – a dynamic economic model representing the world’s forestry sector.

They used it to predict future forest land area, management, trade and greenhouse gas fluxes, factoring in carbon pricing. According to Austin, the model improves on previous studies, which had lower estimates, by capturing leakage – how activities in one region influence markets and activities in others.

“For example, if delayed harvests in one area increase the cost of timber, harvests might proceed more rapidly in another region,” she says, “resulting in smaller total quantity of avoided greenhouse gas emissions than if we measured the impact of the initial harvest delay alone.”

But little has been done to estimate the global costs of achieving this. The authors hope the analysis will help prioritise resources and inform more efficient policies to reduce emissions. To achieve the 1.5-degree-Celsius target, they calculate that carbon prices would need to reach $281 per tonne of CO₂ in 2055.

The study assumes this global carbon price can be implemented consistently across all nations and doesn’t factor in related costs.

“We do not consider transaction costs of pricing carbon,” says Austin, “which include costs of setting up institutional frameworks for financing, consultation and participation, and the costs of systems for monitoring reporting and verification, which could be substantial.”

Still, it seems trifling compared to the hundreds of trillions of dollars unchecked warming could mount to.

Austin and co-authors also note that, among other things, future research should factor in “potential impacts of climate change on forest growth and productivity”.

Indeed, studies reveal trees’ capacity to store carbon is not finite, suggesting that protecting forests, while vital, should not replace strategies to reduce emissions.