The three screen doors: can marine "protected" areas be effective?

The great majority of marine protected areas (MPAs) fail to meet their management objectives. So MPAs can be effective conservation tools, we recommend two paradigm shifts, the first related to how they are located and the second related to how they are managed. MPAs are unlikely to be effective if they are located in areas that are subject to numerous, and often uncontrollable, external stressors from atmospheric, terrestrial, and oceanic sources, all of which can degrade the environment and compromise protection.