Experts in forestry say a huge program of tree planting is needed if the world is to have any chance of reducing its carbon emissions to effectively zero. They also say that the aim, though difficult, is feasible but will depend on careful planning - "to get the right trees in the right places", as one specialist put it.
Finding enough land may be one of the toughest challenges. Farmers will want incentives to convert their fields to forests, not just to help with the cost of planting trees but also to compensate them for the long decades before they can earn an income from them.
Prime agricultural fields are unlikely to be selected for this role but areas currently used for livestock may be in line, and that might force countries to make some highly sensitive choices between producing meat and growing forests.
It could also mean a profound change to the look of much of the countryside, with the familiar sights of grazing cattle and sheep replaced by woodland.
Urban areas may offer scope for planting but these will be relatively small and possibly more expensive.
Specialists also comment that the effort has to be properly funded and "joined-up", which means coordinating many different government agencies, forestry organizations, and farmers - no easy task.