Effects of Marine Reserves
Typically when a marine reserve is established, the goal is to increase the abundance and diversity of marine life inside. Scientific research shows that marine reserves consistently accomplish this goal.
More Fishes, Shellfish, and Other Marine Life
Considerable scientific documentation—published in peer-reviewed journals—provides a clear picture of what has happened after the establishment of marine reserves.
Scientists have studied more than 124 marine reserves around the world and monitored biological changes inside the reserves.
The number of species in each study ranged from 1 to 250.
As indicated in the top graph, the studies documented a wide range of changes inside marine reserves, but nearly all of the effects were positive. A global review of the studies revealed that fishes, invertebrates, and seaweeds had the following average increases inside marine reserves:
- Biomass, or the mass of animals and plants, increased an average of 446%.
- Density, or the number of plants or animals in a given area, increased an average of 166%.
- Body size of animals increased an average of 28%.
- Species diversity, or the number of species, increased an average of 21% in the sample area.
Heavily fished species often showed the most dramatic increases. Some fished species had more than 1000% higher biomass or density inside marine reserves. Even small changes in species diversity and individual body size are important; these values have less potential for change than biomass or density.
The Evidence