Urban Forests Act of 2021 This bill provides for support to maintain urban forests. The Department of Agriculture (USDA) shall establish a grant program to be known as the Tree City USA Grant Program to provide competitive grants to qualifying local governments to enhance and maintain urban forests. USDA and the Department of Labor shall jointly establish Civilian Conservation Centers in urban and community areas. A specified five-year report on state forests and their resources shall contain an analysis of forest carbon over the previous two decades. Such report shall demonstrate the efforts taken by the Forest Service to conduct a strategic national forest inventory by measuring field plots in combination with advanced technology to improve data, information, and estimates of precision; and use advanced geospatial technologies to improve the area and volume estimates of those field plots, especially for sub-state regions and smaller areas. USDA shall enter into a memorandum of understanding with the Departments of Health and Human Services, Housing and Urban Development, the Interior, Labor, and Transportation and the Environmental Protection Agency to identify strategies to increase equitable access to urban forests through existing programs and authorities; and conduct research on the benefits of urban forests for air quality, heat island mitigation, energy burden reduction, and enhanced shading for heat-resilient housing and active transit.