lakes and streams near areas of habitat are used for recreation and relaxation. Habitats, damp or dry, and nature reserves are managed and these areas contribute to maintain biodiversity. Population The population of Switzerland is heavily urbanised. In 2009, 74% of the 7,785,800 inhabitants lived in urban areas. The distribution of population is shaped by the topography of the country, the plateau being the most populous area and including the major cities of Switzerland. With a population density of 450 inhabitants per km2, it is one of the most densely populated region in Europe. There are large disparities of population densities between the cantons lying in the plateau and those lying in the Alps. Thus, the population densities of the cantons of Lucerne, Solothurn and Zurich are respectively 261.0, 319.7 and 813.6 inhabitants per km2. On the other hand, the cantons of Uri and Graubünden have very low population densities, respectively 33.4 and 27.0 inhabitants per km2. In the southern Alps, the canton of Ticino also has a population density less than the national average, with 122.5 inhabitants per km2 (against 194.7). Environment With the delicate alpine and glacial environments making up a significant portion of the country and providing a major industry, Switzerland has been concerned with environmental issues. Some of the main issues are listed below. Air The main environmental issues in Switzerland's air is air pollution from vehicle emissions and open-air burning as well as acid rain. In 2004, the average amount of carbon dioxide (CO2) emissions per resident was and in 2005 was . With these numbers, Switzerland is 31st to 33rd among the 45 nations listed by United Nations Millennium Development Goals Indicators as developed nations and 69th worldwide. In 2009 Switzerland announced that they expected by 2010 to reduce their total greenhouse gas emissions by 8% to 10% over emissions in 1990. The population () uses 3.76 tonnes of oil equivalent per person per year, of which 43.7% comes from petroleum and 19% from nuclear power. Water The major water issue in Switzerland is water pollution from the increased use of agricultural fertilizers as well as hydrocarbon pollution from transport and industry. While improvements have been made, there are still issues with eutrophication (an increase in nitrogen and phosphates) in many lakes in the Swiss Plateau. The total renewable water resources of Switzerland, , totals , of which the total freshwater withdrawal is per