Rockfish Like national parks on land, Marine Protected Areas (MPAs) can be used to protect biologically rich ecosystems and help restore overfished populations. There is compelling evidence that MPAs have rapid and lasting effects. MPAs are proven to increase size, numbers and diversity in fish populations. Even temporary closed areas can be a powerful tool in fisheries management. Currently, MPAs cover less than one percent of the world's oceans; by comparison, there's similar protection for four percent of Earth's land area. This trend is slowly changing as MPAs become more popular across the globe. Many nations have plans to protect 10 percent or more of their ocean areas with MPAs over the next decade, and California is in the final stages of implementing the first statewide network of MPAs in the U.S.