The Convention on Biological Diversity's Aichi Target 11 mandates that 17% of terrestrial and 10% of marine environments be conserved in protected areas by 2020. Such simple numeric indicators act as motivators and a measure of progress. But striving to meet the stipulated coverage should not compromise the convention's broader goal of maximizing biodiversity.

Area coverage is the only element of Target 11 that is on track, at least on land (D. P. Tittensor et al. Science 346, 241–244; 2014). Other crucial elements are effective, equitable biodiversity management; ecological representation of a mix of ecosystems; and connectivity between sites to allow species dispersal. Some species and ecosystems may be lost if implementation of these elements is delayed much longer.

Focusing on area coverage alone risks creating perverse outcomes. It encourages the proliferation of large protected areas that are under little threat, and neglects areas where protection is most needed (see and If not considered in the context of other elements of Target 11, maximizing the area under protection increases the financial and political cost of meeting the same biodiversity goals. As with other global policy goals (see S. Fukuda-Parr J. Hum. Dev. Capab. 15, 118–131; 2014), the abstract global target has created unintended consequences for national conservation planning.

With negotiations beginning in 2016 for the next tranche of the convention's targets, new incentives are needed to emphasize the pivotal additional elements of Target 11.