Cities are overheating: is greenery really a solution?

Every summer seems to follow the same script: new heatwaves, record temperatures, and increasingly difficult nights. But those who live in cities know this well: the heat felt among buildings, paved streets, and fully paved squares is often much more intense than in surrounding green areas or the countryside.

It is not just a feeling. It is a well-known phenomenon among scientists, called an urban heat island (Urban Heat Island), which turns cities into veritable heat reservoirs. With ongoing climate change, this effect is becoming increasingly evident and represents one of the main challenges for the design of urban spaces. The good news is that there are concrete solutions. And one of the most effective has always been right before our eyes: greenery.

• Why is it hotter in cities?
• Greenery is a real climate infrastructure
• Even small gardens make a difference

Why is it hotter in cities?

Artificial surfaces absorb and store enormous amounts of solar energy during the day. Asphalt, concrete, bricks, and building roofs reach very high temperatures and slowly release the stored heat even after sunset. For this reason, cities cool down with greater difficulty than rural areas, where natural soil and vegetation help maintain more balanced temperatures.

According to the European Environment Agency (EEA), temperatures in urban areas can be 4-8 °C higher than in surrounding areas, especially during summer nights. And it is precisely the lack of adequate nighttime cooling that increases the health risk, particularly for the elderly, children, and more vulnerable people. With the increase in heatwaves expected in the coming decades, rethinking cities is no longer just a matter of aesthetics, but a climate adaptation necessity.

The first way to do this is by considering the importance of trees: they are among the most effective natural systems for lowering the temperature of the surrounding environment, and they do so through two complementary mechanisms.

The first is shading. The canopy intercepts part of the solar radiation, preventing the sun from directly hitting the ground, buildings, and paved surfaces. This means less stored heat and lower temperatures. The second is even more interesting: evapotranspiration. Through their leaves, plants release a small amount of water into the air in the form of vapor. This process requires energy and produces a natural cooling effect, very similar to what we experience when sweat evaporates from our skin. For this reason, areas rich in vegetation are often noticeably cooler than completely sealed spaces.

Greenery is a real climate infrastructure

For many years, urban greenery was considered above all a decorative element. Today we know that its role is much more important. Trees, shrubs, lawns, and permeable soils help reduce temperatures, improve air quality, promote rainwater infiltration, and contribute to urban biodiversity.

For this reason, urban planners and climatologists are increasingly talking about green infrastructure or even climate infrastructure: natural systems designed to help cities cope with the effects of climate change.

Naturally, increasing the number of trees is essential, but it is not enough on its own. Greenery really works when it is designed as an ecosystem. A tree surrounded by asphalt and concrete, with compacted soil poor in organic matter, will have greater difficulty growing and offer more limited benefits. It is therefore essential to also take care of the soil, promote the presence of vegetation at different levels – trees, shrubs, groundcovers – and reduce impermeable surfaces whenever possible.

Also the choice of species plays an important role. In an increasingly hot climate characterized by long periods of drought, using plants naturally adapted to Mediterranean conditions means creating more resilient green spaces that are less dependent on irrigation and maintenance.

Even small gardens make a difference

When talking about climate change, we often think of large-scale interventions. In reality, private spaces can also help make cities more livable. Every vegetated surface represents a small area capable of absorbing heat, retaining rainwater, and providing refuge for pollinating insects and other forms of biodiversity.

A garden designed with ecological criteria, an alternative lawn that requires less water than a traditional grass lawn, soil kept alive thanks to mulching, or the choice of Mediterranean species suited to the local climate are all actions that, added together, contribute to improving the urban microclimate. They will not solve the problem of global warming on their own, but they can make our cities more resilient and more comfortable.

Heatwaves are no longer exceptional events. They are destined to become an increasingly frequent component of Mediterranean summers. Faced with this reality, greenery can no longer be considered a mere ornamental element. It is a resource that helps mitigate heat, protects biodiversity, improves quality of life, and makes urban spaces more capable of adapting to climate changes. Every new tree, every permeable flowerbed, every garden designed in balance with the climate represents a small piece of a broader transformation.