An urban wild is a remnant of a natural ecosystem found in the midst of an otherwise highly developed urban area.^[1][2]

One of the most expansive efforts to protect and foster urban wilds is the aptly titled "Urban Wilds program" conducted in Boston, which had its start in 1977 off the back of a 1976 report by the Boston Planning & Development Agency (BPDA), formerly the Boston Redevelopment Authority (BRA).^[3][4]

Urban wilds, particularly those of several acres or more, are often intact ecological systems that can provide essential ecosystem functions such as the filtering of urban run-off, the storing and slowing the flow of stormwater, amelioration of the warming effect of urban development, and generally benefiting local air quality.^[1][5]

Typically, urban wilds are home to native vegetation and animal life as well as some introduced species.^[6][7][8] Urban wilds are vital to species of migratory birds that have nested in a given area since prior to its urbanization.^[5][7][9]

Without formal protection, urban wilds are vulnerable to development. However, achieving formal protection of a large urban wild can be difficult. Land tenure of a single ecological area can be complex, with multiple public and private entities owning adjacent properties.^[10][11]

Key strategies used in the preservation of urban wilds have included conservation restrictions that keep complex land tenure systems in place while protecting the entire landscape. Public/private partnerships have also been successful in protecting urban wilds.^[10]

The urban wilds prioritized by municipalities tend to be partial wetlands that perform a range of ecological services while contributing to the biological diversity of the region.^[12]

มีการถกเถียงกันว่าพื้นที่ธรรมชาติที่ไม่ได้มีขนาดที่เหมาะสมที่จะให้บริการระบบนิเวศ อย่างมีนัยสำคัญ ควรจัดประเภทเป็นสวนสาธารณะแบบพาสซีฟแทนที่จะเป็นป่าในเมืองหรือไม่ ป่าในเมืองขนาดเล็กใช้สำหรับการพักผ่อนหย่อนใจแบบพาสซีฟและมีคุณค่าต่อเมืองน้อยกว่าในแง่ของการเสริมสร้างการทำงานของระบบนิเวศ^{[ 13 ]}