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Limiting global warming to 1.5°C over pre-industrial levels is only possible if we make better use of the world’s forests, which collectively act as a huge carbon sink. But maximising the strength of this carbon sink won’t be cheap: it might cost about $393 billion per year.

Kemen Austin at RTI International, a non-profit research firm in the US, and her colleagues have examined the financial costs of mitigating the impacts of greenhouse gases through forests.

They estimate that as much as 6 gigatonnes of carbon dioxide per year could be sequestered by forests by 2055, but only if forestry managers are incentivised to keep carbon in their forests. Encouraging this would require payments equivalent to $281 per tonne of sequestered CO2.

The researchers used an economic model known as the global timber model, which looks at the forestry sector and predicts how forest management practices – and greenhouse gas emissions – would be affected by such carbon-sequestration pricing.

“For example, a forest manager might decide to lengthen harvest rotations and thus store additional carbon, if compensated for foregone revenue from shorter harvest cycles,” says Austin.

Likewise, such compensation may mean managers are also encouraged to devote more efforts to afforestation – planting trees in areas that hadn’t previously been forest.

The researchers found that financially discouraging tropical deforestation would have the largest impact, responsible for at least 30 per cent of the total mitigation.

How the incentives would be financed is an open question. Given the uneven distribution of forests worldwide, Austin acknowledges that there may be an undue financial burden on governments in tropical regions.

“Solving global climate change is going to require mitigation across all sectors of the economy: industry, transportation, electricity and, of course, forests,” says Austin.

“Protecting, managing, restoring forests is important for climate change mitigation, but it also has really important co-benefits like biodiversity protection,” she says.