The environment of Belgium is generally affected by the high population density in most of the country. However, due to consistent efforts by the various levels of government in Belgium, the state of the environment in Belgium is gradually improving. These efforts have led to Belgium being ranked as one of the top 10 countries (9 out of 132) in terms of environmental protection trends. However, water quality still suffers from a relatively low, yet increasing percentage of sewage waste-water treatment, and from historical pollution accumulated in sediments. Air quality is generally good to average, but is affected by emissions from traffic and house heating, and industrial air pollution blowing over from the neighboring heavily industrialized Ruhr-area in Germany. Biodiversity is lower in