Integrating the historical legacy of redlining on street tree communities into current IPM and tree planting efforts in cities

Due to recent initiatives recognizing the importance of canopy cover for the health of city residents, many U.S. cities are embarking on substantial tree-planting campaigns. For entomologists, these efforts provide a rare opportunity to imbue 'cultural' integrated pest management (IPM) practices into planting efforts. When doing so, it may be important to consider both environmental heterogeneity and socio-ecological legacies in the urban landscape. We present recent work illustrating how one such widely applied hidden geography, the federally mandated 1937 classification of neighborhoods into grades of loan risk—from most desirable (A = green) to least desirable (D = “redlined”)—using racially discriminatory criteria, is reflected in current street tree community structure in Baltimore, MD. We find neighborhoods that were redlined have consistently lower street tree α-diversity and are nine times less likely to have large (old) trees occupying a viable planting site. Simultaneously, redlined neighborhoods are locations of recent tree planting activities, with a high occupancy rate of small (young) trees. However, the community composition of these young trees exhibits lower species turnover and reordering across neighborhoods compared to those in higher grades due to heavy reliance on a few tree species. As a result, they are likely to be more vulnerable to insect pests or diseases as the community ages. In these neighborhoods, cities could use a targeted strategy of planting diverse tree cohorts paired with investments in site rehabilitation and maintenance. Such additional inputs may be necessary if cities wish to overcome ecological feedbacks associated with legacies of environmental injustice.