Polluted protected areas

Artificial light can have large consequences for stream communities – aquatic insects, for example, are less likely to drift downstream in the presence of streetlights. Because some aquatic organisms use natural variations in sunlight as cues telling them when and where to migrate, or eat, or gather up into a group, artificially altered light patterns can disrupt those behaviors.

Marine protected areas, despite their status as ocean zones that have been set aside and (to some extent) shielded from human impacts, are affected by light pollution, too.

A group of researchers from the University of Exeter, in the United Kingdom, recently published an analysis of just how much artificial light is reaching the global network of marine protected areas. By analyzing satellite images taken at night, the scientists were able to quantify the extent of light pollution within marine protected areas, and how that number changed over 20 years, between 1992 and 2012.

The researchers found that in 2012, 35 percent of the protected areas they analyzed were exposed to some degree of artificial light. Of those areas, more than half experienced “widespread” light pollution, indicated by visible illumination present in all of the image pixels within the protected area.

Furthermore, although the majority of protected areas did not experience any change in artificial light levels over the 20 years the scientists analyzed, light pollution increased in 14.7 percent of the protected areas. (The authors note, however, that a lack of change doesn’t indicate a lack of light pollution – it simply means that light levels were constant between 1992 and 2012.)

“Given the importance of light in guiding the behaviors of many marine species,” the authors write, “these results suggest that nighttime lighting may influence the ecology of many of the most valued regions of the ocean.”

The first step in mitigating the negative consequences of artificially illuminating marine protected areas is to determine the extent of the problem. Now that researchers are aware of which areas are particularly impacted by light pollution, resource managers can begin addressing the problem by “[s]witching off, dimming or shielding lights, preserving naturally dark landscapes, and limiting use of spectra known to cause ecological impacts,” among other possible solutions.

Marine protected areas provide shelter from human activities for marine organisms like the sea lion pictured here. 

(Image by NOAA's National Ocean Service via Flickr/Creative Commons license)