Why are trees important? 'If we keep them, cities will become concrete ovens'
Fran Poštenjak, Croatia's first doctor for trees, warns that without urban trees, Croatian cities risk becoming concrete ovens. He emphasizes that mature trees provide cooling, water retention, and other ecological benefits, which are crucial for climate resilience. The loss of trees is not just aesthetic but also financial, leading to higher cooling costs, increased pressure on healthcare systems, flood risks, and decades of waiting for new trees to replace lost functions. Scientific research confirms that proximity to urban greenery reduces stress, mitigates heat islands, cleans air, retains rainwater, and protects health from extreme heat. Poštenjak argues that investing in quality tree planting is an investment in safety, health, and city resilience. This season's droughts will have visible effects by autumn, with trees suffering irreversible damage due to high temperatures and lack of water.
Fran Poštenjak, the first Croatian doctor for trees, has issued a stark warning that without urban trees, Croatian cities will become "concrete ovens." His comments come amid rising concerns over extreme heatwaves, prolonged droughts, and the increasing vulnerability of urban greenery. According to Poštenjak, the loss of mature trees is not just an aesthetic issue, it represents a massive financial burden and a threat to public health, infrastructure resilience, and climate adaptation efforts. The warning comes as Croatia, like much of Europe, faces unprecedented levels of heat, with temperatures regularly exceeding 35°C during summer months. The period from June to September, which marks the peak of vegetation growth, has seen a sharp decline in rainfall, placing immense stress on urban tree populations. Urban trees, which provide essential cooling, air purification, and flood mitigation benefits, are among the first casualties of these environmental pressures. Poštenjak emphasizes that without proper watering and strategic planting, cities risk losing their primary defense against extreme heat, potentially transforming into "concrete ovens." Urban trees play a critical role in mitigating the effects of urban heat islands, areas where built environments absorb and retain more heat than surrounding rural areas. Studies have shown that proximity to urban greenery reduces stress, improves air quality, retains rainwater, and protects public health from the impacts of extreme weather. Mature trees, especially large ones such as oaks, beeches, and maples, are particularly effective in providing shade, reducing noise pollution, and increasing property values. They also contribute to improved mental and physical well-being among residents. However, the current state of urban forests in Croatia is under severe strain. During periods of intense heat, the water consumption of mature trees can increase dramatically, from around 150 to 200 liters per day at moderate temperatures to over 600 liters daily when temperatures exceed 35°C. This increased demand is exacerbated by the prevalence of asphalt and concrete surfaces, which trap and radiate heat, further intensifying the stress on trees. Without adequate irrigation and soil preparation, urban trees face a high risk of long-term damage or death. One of the most alarming consequences of prolonged drought is the phenomenon known as "summer branch drop," where heavy lower branches of mature trees break unexpectedly due to weakened structures. This poses a direct danger to pedestrians and property. In addition, extended dry spells lead to visible signs of distress in trees, including leaf drop, wilting, and even complete dieback of parts of the plant. These symptoms often go unnoticed until late autumn, when the true extent of the damage becomes apparent. Another major challenge facing urban trees is compacted soil, a result of years of foot traffic, vehicle movement, and construction activities. Compacted soil prevents water and air from reaching tree roots, making them highly susceptible to dehydration and disease. Poštenjak stresses that proper planning and maintenance are crucial to ensuring the survival of urban trees. He advocates for deep root watering, high-quality soil, and careful planting techniques to build resilience against future climatic shocks. In response to the growing crisis, experts emphasize the need for proactive measures rather than reactive solutions. Planning for tree resilience should begin before planting, not after damage occurs. This includes selecting appropriate species, preparing suitable soil conditions, and implementing sustainable irrigation strategies. With climate change continuing to drive more frequent and severe heatwaves, the importance of urban trees as a key component of city infrastructure, and as a vital tool in building climate resilience, has never been clearer.
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