Association of land use and its change with beach closure in the United States, 2004-2013.

Land use and its change have great influences on water quality. However, their impacts on microbial contamination of beach water have rarely been investigated and their relationship with beach actions (e.g., advisories or closure) is still unknown. Here, we analyzed beach closure data obtained from 2004 to 2013 for >500 beaches in the United States, and examined their associations with land use around beaches in 2006 and 2011, as well as the land use change between 2006 and 2011. The results show that the number of beach closures due to elevated indicators of health risk is negatively associated with the percentages of forest, barren land, grassland and wetland, while positively associated with the percentages of urban area. The results from multi-level models also indicate the negative association with forest area but positive association with urban area and agriculture. The examination of the change of land use and the number of beach closures between 2006 and 2011 indicates that the increase in the number of beach closures is positively associated with the increase in urban (β=1.612, p<0.05) and agricultural area including pasture (β=0.098, p<0.05), but negatively associated with the increase in forest area (β=-1.789, p<0.05). The study suggests that urbanization and agriculture development near beaches have adverse effects on beach microbial water quality, while afforestation may protect beach water quality and reduce the number of beach closures.