Within the province, various Regional Districts and municipalities have enacted laws to control pollution. There are also area-based plans to manage pollution along geographic lines that recognize airsheds instead of political boundaries. This system is especially relevant to BC because of its mountainous topography. The BC Environmental Management Act recognizes airsheds and notes that managers under the Act "may give consideration" to them, but their full legal status is uncertain. Some plans have had a considerable effect, and this trend is likely to continue.