Andrey Nekrasov/imageBROKER/REX/Shutterstock Conservationists are still arguing about exactly how much of the world’s oceans should be protected to ensure marine life does well. The UN Convention on Biological Diversity has a goal of 10 per cent by 2020. And at the International Union for Conservation of Nature’s World Conservation Congress last year, a headline-grabbing target of 30 per cent by 2030 was endorsed. But such targets may miss the point. Are our existing marine protected areas (MPAs) doing a good job of conserving the biodiversity they were designed to safeguard?