Actual experience, as well as extensive scientific research, shows that offshore oil platforms provide considerable habitat for marine organisms even when they are in full operation. Invertebrates like mussels and barnacles attach themselves to the steel structures, forming additional habitat by encrusting pilings and pipes as well as covering the bottom. This habitat in turn supports a vast array of fish. Some fish species are present in greater numbers around oil platforms than at natural reefs off California. The immense size and extensive vertical profile of these structures promote the growth and development of large populations of diverse marine organisms. A 2014 study published in the Proceedings of the National Academy of Sciences found that California’s offshore platforms are among the most productive marine habitats in the world, ten times more productive than marine estuaries.