A leading strategy in international efforts to reverse ongoing losses in biodiversity is the use of protected areas. We use a broad range of data and a review of the literature to show that the effectiveness of existing, and the current pace of the establishment of new, protected areas will not be able to overcome current trends of loss of marine and terrestrial biodiversity. Despite local successes of well-designed and well-managed protected areas proving effective in stemming biodiversity loss, there are significant shortcomings in the usual process of implementation of protected areas that preclude relying on them as a global solution to this problem. The shortcomings include technical problems associated with large gaps in the coverage of critical ecological processes related to individual home ranges and propagule dispersal, and the overall failure of such areas to protect against the broad range of threats affecting ecosystems. Practical issues include budget constraints, conflicts with human development, and a growing human population that will increase not only the extent of anthropogenic stressors but the difficulty in successfully enforcing protected areas. While efforts towards improving and increasing the number and/or size of protected areas must continue, there is a clear and urgent need for the development of additional solutions for biodiversity loss, particularly ones that stabilize the size of the world’s human population and our ecological demands on biodiversity.

Ongoing global biodiversity loss ...