Ground subsidence tied to fish farming

Nature : Ground levels are known to drop in areas of extended oil drilling, as in Houston, Texas, and groundwater pumping, as in Bangkok, Thailand. A new study of China’s Yellow River delta has identified a major side effect of subsidence. Stephanie Higgins of the University of Colorado Boulder and her colleagues examined satellite-radar images of the region. By using the roofs of farmhouses as a reflective surface, they were able to determine the changes in ground height. Water pumping for fish farms appears to have caused ground levels to drop by as much as 0.25 m per year in the area. And because the delta empties into the sea, the subsidence has caused local sea levels to rise 100 times as quickly as the global average. The connection between aquaculture and local sea levels is a new concern for both industry and researchers. The Yellow River delta is particularly vulnerable to shoreline and ground height changes, despite major projects to reduce erosion. Understanding the impact of fish farming could help control future damage.