Beyond Counting Trees: Why Cities Need the Right Trees in the Right Places

Van Quy Khuc

VNU University of Economics and Business, Vietnam National University

18-05-2026

© Wix

As cities continue to grow, the world is becoming increasingly urban. By 2023, nearly 57% of the global population lived in urban areas. Cities bring opportunities for economic development and innovation, but they also create a difficult ecological trade-off: the expansion of roads, buildings, and infrastructure often comes at the expense of natural systems (Panagopoulos, González Duque, & Bostenaru Dan, 2016; Ameen & Mourshed, 2017). As natural spaces disappear, cities become more vulnerable to urban heat, air pollution, flooding, and declining carbon storage capacity.

To address these problems, researchers and policymakers have increasingly turned toward Nature-based Solutions (NbS): strategies that use natural systems to tackle environmental challenges. In cities, these solutions are commonly implemented through green infrastructure such as parks, street trees, rain gardens, and green roofs. Trees are particularly important because they provide multiple ecological benefits simultaneously. Their canopies intercept rainfall, reduce heat by shading surfaces, capture air pollutants, and store carbon through photosynthesis.

However, many urban greening initiatives still rely on a deceptively simple question: How many trees should we plant? Numerical targets—such as increasing green coverage or planting one million trees—are attractive because they are visible and easy to measure. Yet counting trees alone may overlook a more important issue: not all trees contribute equally to ecological outcomes.

Different species possess different ecological strengths. Some species are more effective at reducing urban heat, while others excel at managing stormwater or storing carbon. Moreover, cities themselves are ecologically uneven. One neighborhood may struggle with flooding, another with extreme heat, and another with poor air quality. Treating every location and every tree species as interchangeable risks missing opportunities for greater ecological impact.

A recent study by Dong and colleagues published in npj Urban Sustainability addressed this challenge through an optimization framework linking local environmental needs with species-specific ecological performance. Using Philadelphia as a case study, researchers analyzed 0.25 km² urban grids and identified tree compositions that could maximize ecosystem services. Their findings revealed that Philadelphia’s current species distribution is not optimal. Increasing advantageous species such as silver maple (Acer saccharinum), red maple (Acer rubrum), and sweetgum (Liquidambar styraciflua) could substantially improve outcomes, delivering approximately 20% greater stormwater management and up to 80% stronger microclimate regulation compared with current conditions (Dong et al., 2026).

Urban ecosystems are not simply collections of isolated objects but networks of interacting socio-ecological systems. Trees, climate conditions, human activities, and urban infrastructure constantly influence one another. Focusing only on the number of trees reduces this complexity into a single simplified indicator. Such simplification may create an “eco-deficit” mindset where greenery becomes a symbolic checkbox rather than a functioning ecological system (Khuc & Nguyen, 2026).

Rather than asking “How many trees can we plant?”, city planners and policy makers should start to ask “Which trees, in which places, can best help both humans and nature thrive together?” This shift may seem small, but it changes urban greening from decorating cities to redesigning how cities coexist with nature (Vuong, 2025; Nguyen & Ho, 2026).

References

Ameen, R. F. M. & Mourshed, M. (2017). Urban environmental challenges in developing countries—a stakeholder perspective. Habitat International, 64, 1–10. https://doi.org/10.1016/j.habitatint.2017.04.002

Dong, X., et al. (2026). Optimizing urban tree species composition to maximize nature-based solutions. npj Urban Sustainability, 6, 47. https://doi.org/10.1038/s42949-026-00361-w

Fu, D., et al. (2019). Investigation on the carbon sequestration capacity of vegetation along a heavy traffic load expressway. Journal of Environmental Management, 241, 549–557. https://doi.org/10.1016/j.jenvman.2018.09.098

Guo, J., et al. (2023). Nationwide urban tree canopy mapping and coverage assessment in Brazil from high-resolution remote sensing images using deep learning. ISPRS Journal of Photogrammetry and Remote Sensing, 198, 1–15. https://doi.org/10.1016/j.isprsjprs.2023.02.007

Khuc, V. Q. & Nguyen, M. H. (2026). Cultural Additivity Theory. https://books.google.com/books?id=Y4XZEQAAQBAJ

Nguyen, M. H., & Ho, M. T. (2026). The absurdist approach to unveiling possible paradoxical thinking for innovative socio-psychological research. MethodsX, 16, 103910. https://doi.org/10.1016/j.mex.2026.103910

Panagopoulos, T., González Duque, J. A., & Bostenaru Dan, M. (2016). Urban planning with respect to environmental quality and human well-being. Environmental Pollution, 208, 137–144. https://doi.org/10.1016/j.envpol.2015.07.038

Vuong, Q. H. (2025). Wild Wise Weird. AISDL. https://books.google.com/books?id=C5dDEQAAQBAJ