The Convention on Biological Diversity (CBD) agreed in 2010 to restore “at least 15 per cent of degraded ecosystems” by 2020 (www.cbd.int/sp/targets). In Finland's experience, this target is unrealistic.

Ecosystem destruction is measured according to the expanse and degree of degradation. Consequently, under the CBD agreement, damage to an ecosystem's condition needs to be reduced by 15% over an entire area of degraded landscape or, for example, by 33% in a randomly selected 45% of that area to attain the same reduction.

There are considerable challenges in achieving this reduction: heavy restoration measures must be completed across large areas and in a short time, while compensating for ongoing degradation elsewhere.

Finland's forests cover roughly 15 million hectares, 95% of which have been degraded by forestry operations. To meet the CBD target, the country would need to reduce degradation by 33% in more than 100,000 hectares each month until 2020.

It has already taken Finland almost 30 years to restore some 30,000 hectares of forest (see Table 2.5 at go.nature.com/pajic9) — one-thousandth of the CBD's monthly requirement.

There is a danger that parties to the CBD will ignore the target because of its sheer impracticality.