The regional park wildlands reflect the plant communities of the Bay Area: They contain a diverse mixture of native and non-native trees, shrubs, and annual and perennial herbaceous plants. Although the flora has changed considerably as a result of non-native plant introductions and increased urbanization, numerous native plants remain. Land use and vegetation changes over the past two centuries have irreversibly altered the landscape, making it necessary to use management techniques to maintain an ecological balance between native and non-native vegetation and to achieve wildland fire safety objectives. All District vegetation management activities are designed to maintain plant community dynamics. The District manages most plant communities to preserve their intrinsic value as naturally functioning ecosystems.