Urban green infrastructure: science and planning for more livable cities

The discussion features the participation of Víctor Moralo, partner and sustainability director at ECIJA; Óscar Martínez Gaitán, agricultural engineer and founder of Los Árboles Mágicos; and Antonio Delgado, a PhD in Geology and research professor at the CSIC at the Institute of Earth Sciences, who provides a scientific perspective to the discussion.

The debate is based on a central idea: urban trees can no longer be considered merely ornamental elements or open spaces within urban planning. In the current context, marked by climate change, rising temperatures, and the need to adapt cities, green infrastructure takes on a much broader role. Its value lies in the ecosystem services it provides: generating shade, reducing the heat island effect, improving air quality, regulating humidity, absorbing pollutant particles, reducing noise, creating spaces for socializing, and enhancing the physical and mental well-being of citizens.

From a legal perspective, Víctor Moralo situates the debate within the European and Spanish regulatory framework, highlighting the growing importance of ecosystem restoration, biodiversity, and the integration of climate criteria into urban planning. In this regard, he points out that cities must incorporate sustainability transversally into their planning instruments, not as an accessory issue, but as a necessary condition to improve their resilience and quality of life.

Antonio Delgado introduces a relevant scientific point: urban parks and trees should not be presented simplistically as major sinks for CO₂ capable of compensating for global climate change. Their contribution to planetary photosynthesis is limited in quantitative terms. However, their importance is enormous at a local scale. Urban green spaces help reduce temperatures through shade and evapotranspiration, contribute to the retention of pollutant particles such as PM10 and PM2.5, help mitigate certain gases present in cities, and generate small ecosystems where soil, water, fungi, birds, insects, and vegetation interact.

The debate places particular emphasis on the fact that urban green spaces must be designed with the same rigor as any other infrastructure. Óscar Martínez Gaitán explains that it would make no sense to build a building or a bridge without adequate foundations, but often large trees are planted in inadequate planting pits, without space for root development or proper planning for their future growth. This lack of technical criteria can lead to tree health issues, tree falls, unnecessary pruning, and reduced effectiveness of the services they are expected to provide.

One of the key points of the debate is the criticism of a purely aesthetic or mechanical approach in the management of green spaces. Participants warn against practices such as systematic pruning without justification, indiscriminate use of machinery, cleaning without regard for biodiversity, or the creation of lawns in places that serve no clear social or environmental purpose. They argue that the management of urban green spaces should be based on technical knowledge, scientific criteria, and proper drafting of ordinances, public contracts, and maintenance specifications.

The conversation also addresses the debate on water and the choice of plant species in urban environments, especially in Mediterranean climates. It is emphasized that it is not enough to talk about native species in general terms, as the city is a deeply transformed environment. The selection of trees and plants should respond to the real conditions of the urban space, water availability, the ability to provide shade, behavior with heat, and specific objectives for each area. In this regard, the need to research new varieties, recover rainwater or gray water where possible, and eliminate lawns that do not serve a clear social function is highlighted.

Another key topic discussed is the social dimension of urban parks. In contrast to a vision focused exclusively on large peri-urban parks, participants emphasize the importance of neighborhood parks, squares, and local green spaces. These places facilitate intergenerational coexistence, foster a sense of belonging to the community, provide spaces for playing, resting, and socializing, and help level the conditions among residents. Therefore, green infrastructure serves not only an environmental function, but also social, cultural, and health-related ones.

The debate concludes with a shared idea: the cities of the future will not be more sustainable simply by incorporating more green space, but by planning it better. Urban green infrastructure requires a transversal approach that connects science, urban planning, law, public procurement, maintenance, health, and citizen participation. The “magic trees” are not so for some abstract or symbolic quality, but for their real capacity to transform urban life when they are planted, cared for, and managed with attention.

With this latest installment of Meetings with Scientists, Science in Society opens a space for reflection on one of the great urban challenges of our time: understanding that green spaces are not merely an ornament of the city, but an essential infrastructure for its adaptation, livability, and future.

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