If there were any Frisii left in Frisia, they fell victim to the whims of nature, civil strife and piracy. After several hundred years of favorable conditions, the natural environment in the low-lying coastal regions of northwestern Europe began to deteriorate c. 250 AD and gradually worsened over the next 200 years. Rising sea levels and storm surges combined to flood some areas. Many deserted village sites were silted over. The situation was probably aggravated by a shift to a cooler, wetter climate in the region as well as by the introduction of malaria and other epidemic diseases.