The Legacy of the Past on the Current Composition of Yerba Buena's Urban Trees

Urban trees provide multiple socio-environmental benefits, and their condition and characteristics are influenced by the population's activities and preferences, which change over time. Because trees are long-lived organisms, many of those we see today are a legacy of past generations who chose to plant and care for them.

However, we know very little about the temporal dynamics of urban trees—that is, how their composition, structure, or condition changes over time—especially in Latin America cities. In many cities, periodic censuses of urban trees are lacking, and those that do exist are generally quite recent. Therefore, the history of trees in cities is generally unknown.

In this study, recently published in the journal Urban Ecosystems and led by the researcher Sergio Ceballos, we describe the changes experienced by Yerba Buena's trees over time using a different approach, without the need for historical censuses. To do so, we used the database provided by the Municipality of Yerba Buena, which includes nearly 30,000 urban trees surveyed between 2022 and 2023. In addition, we classified the city's neighborhoods by age, differentiating and mapping them according to the period in which they were urbanized. We used various sources of information—aerial photos, historical maps, and satellite images—and mapped neighborhoods age using Google Earth Engine. We also used a tree cover map, which includes both public and private trees, generated by Javier Foguet, a Geographic Information Systems technician at IER.

We combined these three layers of information—census-referenced trees, a neighborhood age map, and a tree cover map—to analyze how the trees changed over time. We assumed that neighborhood age reflects a temporal sequence of changes, and we ordered them from newest to oldest, an approach we often apply to study changes in forest ecosystems.

Among our main findings, we observed that tree cover and diversity, as well as the proportion of old trees, increase with neighborhood age. In contrast, newer neighborhoods have a higher proportion of native species. We also found that several species that were planted in the past are no longer used, mainly because they reach large sizes and can pose a risk.

These results provide a basis for guiding management decisions, helping to define which attributes to promote in each neighborhood, such as diversity, cover, or the presence of native species. At the same time, this work represents a collaboration between the Municipality of Yerba Buena and the Institute, combining information generated by the local government and scientists.