The City of Boulder has created an Urban Wildlife Management Plan which sets policies for managing and protecting urban wildlife.  Also, the city's parks department has volunteers who monitor parks (including wetlands, lakes, etc.) to protect ecosystems.  From time to time, parks and hiking trails are closed to conserve or restore ecosystems.  Traditionally, Boulder has avoided the use of chemical pesticides for controlling the insect population. However, with the threat of West Nile Virus , the city began an integrative plan to control the mosquito population in 2003 that includes chemical pesticides. Residents can opt-out of the program by contacting the city and asking that their areas not be sprayed.