**This blog entry orginally appeared on the website oceanspaces.org.**/p>

“In a world where fisheries and marine biodiversity are continuing to decline, marine protected areas (MPAs) are an essential tool needed to slow and reverse the oceans’ downward trajectory. Scientists have repeatedly shown that MPAs can rapidly increase the biomass and diversity of species in both tropical and temperate ecosystems (PISCO), serving as insurance policies against the impacts of fishing.

Since the 1990s it has been increasingly clear that human activities are reducing the diversity and abundance of marine life on a global scale (MCBI 1998; Norse 1993). The five major causes are: physical alteration of marine ecosystems, pollution in the sea, introduction of alien species, atmosphere changes and —most of all— overexploitation of marine organisms.

Across the globe, fishing is rarely sustainable (Pauly et al. 2002) and often dramatically affects targeted populations, reducing abundance, biomass, and size, affecting the adult fecundity viability of offspring, (Berkeley et al. 2004) and impacting genetic capacity for growth (Law and Stokes 2005). It also causes profound ecosystem changes which affect the diversity and abundance of nontarget species and the structure and composition of seafloor habitats (Chuenpagdee et al. 2003; Dayton et al. 2002; Watling and Norse 1998). The evidence of fishing impacts on marine ecosystems is ubiquitous and compelling (Jackson et al. 2001).

Managing the mortality of species one-by-one is both data-intensive and expensive. So many species have been harmed by overfishing and destructive fishing methods that it would prohibitively costly to manage them all on an individual basis. An overwhelming body of scientific theory and evidence from around the world indicates that effectively managed no-take marine reserves can reverse the effects of overfishing and destructive fishing methods (Lester et al. 2009). In highly protected, well-managed and enforced MPAs diversity and abundance of marine life increases. Fishes reproducing within these areas spill over into surrounding areas and positively benefit surrounding human communities (Halpern et al. 2009).

To date, however, progress in designation of MPAs has been too slow to have widespread effects, and poaching has diminished the effectiveness of many protected areas in the sea, as it has on land. Clearly, accelerated MPA designation, along with effective management and enforcement, is key to biodiversity conservation, fisheries and tourism worldwide.

Marine protected areas, if managed properly, can be an effective way of protecting marine ecosystems and their associated cultural and historical heritage for future generations to experience and enjoy. Although there are many reasons MPA’s are important, some of the best reasons to support them are because:

-MPA’s protect entire ecosystems including habitat and ecosystem function
-MPA’s protect biodiversity at three levels: ecosystem, species and genetic
-MPA’s protect habitats and ecosystems from destructive fishing practices and other harmful human activities, and allow already damaged areas and ecosystems to recover
-MPA’s provide resilience to protect against potentially damaging external impacts, such as global warming and ocean acidification
-MPA’s established at relatively undisturbed areas can serve as benchmarks to compare with altered ecosystems to assess human impact and improve management

These benefits have motivated a number of nations to set goals for MPA coverage of their ocean territories, and international bodies are working to establish MPAs on the high seas.”

Reprinted from: http://mpatlas.org/learn/mpapedia/WhyDoWeNeedMpas/

See also California Dept. of Fish and Wildlife’s MPA site: http://www.dfg.ca.gov/marine/mpa/index.asp