Our review of the scientific evidence for large-scale percentage area conservation targets concluded: 1. The 17 per cent terrestrial and inland waters, and 10 per cent marine and coastal targets from Aichi Target 11 of the Strategic Plan for Biodiversity 2011-2020 are not adequate to conserve biodiversity. 2. Percentage area targets cannot be considered in isolation from the quality considerations. Protected and conserved areas need to be selectively located, well governed, and effectively and equitably managed to conserve biodiversity. 3. There is no unequivocal answer for what percentage of the Earth should be protected. Estimates from studies considering a wide set of biodiversity values are very high; well over 50 per cent and up to 80 per cent. Studies that include a narrower subset of biodiversity values are lower, but rarely under 30 per cent, and always with caveats that they are incomplete estimates. Protected area conservation targets should be established based on the desired outcomes (e.g. halting biodiversity loss by 2030). 4. The global protection of a minimum of 30 per cent and up to 70 per cent, or even higher, of the land and sea on Earth is well supported in the literature. The call for 50 per cent of the Earth is a mid-point of these values and is supported by a range of studies. 5. Implementation of large global percentage area targets can be achieved through differentiating the kinds of areas that need protection at a national scale, supported by nationally determined contributions in accordance with local conditions.