While much of Palau's fragile natural environment remains free of environmental degradation, there are several areas of concern, including illegal fishing with the use of dynamite, inadequate facilities for disposal of solid waste in Koror, and extensive sand and coral dredging in the Palau lagoon. Like the other Pacific island nations, a major environmental problem is global warming and the related rising of sea level. Water coverage of low-lying areas is a threat to coastal vegetation, agriculture, and the purity of the nation's water supply. Palau also has a problem with inadequate water supply and limited agricultural areas to support the size of the population. The nation is also vulnerable to earthquakes, volcanic activity, and tropical storms. Sewage treatment is a problem, along with the handling of toxic waste from fertilizers and biocides.