He turns concrete walls into living forests: Meet the Spanish botanist transforming cities with vertical gardens

In cities filled with concrete, glass and rising temperatures, Spanish botanist Ignacio Solano sees something different in the empty walls around him. Through massive vertical gardens covered in thousands of plants, Solano is helping transform ordinary buildings into living ecosystems that cool the air, reduce pollution and support biodiversity. His work, spread across Europe and Latin America, has become part of a growing movement to make cities greener as climate change drives stronger and more frequent heatwaves. From studying tropical rainforests to building hydroponic living walls on skyscrapers, Solano has spent years turning nature into a practical urban climate solution.Before becoming one of the leading names in vertical garden design, Solano spent more than 14 years studying tropical ecosystems in places such as Colombia’s Chocó rainforest, Madagascar and Réunion Island. His background in biology helped him understand how plants naturally coexist in crowded environments with limited resources.That research later shaped his approach to urban greening. Instead of viewing buildings as lifeless structures, Solano began treating walls as ecosystems capable of supporting hundreds of plant species.Vertical gardens, also known as living walls or green walls, are systems that allow plants to grow directly on building surfaces using specially designed support structures and irrigation systems. Many modern versions are hydroponic, meaning plants grow without soil and instead receive nutrients through water-based systems.The concept gained global attention in the 1980s through French botanist Patrick Blanc, but Solano says Latin American cities have embraced the idea at a much larger scale. Cities such as Buenos Aires, Mexico City and Guatemala City now contain hundreds of vertical gardens attached to homes, offices, hotels and public infrastructure.One of the biggest advantages of vertical gardens is their ability to cool urban environments. Concrete and asphalt absorb heat during the day and release it slowly at night, creating what scientists call the urban heat island effect.Vertical gardens help reduce this by shading buildings and cooling surrounding air through evapotranspiration, the natural process where plants release water vapour into the atmosphere. The vegetation also acts as insulation, helping buildings stay cooler and reducing energy use from air conditioning.Research has shown that green walls can significantly lower building surface temperatures while improving thermal comfort during extreme heatwaves. Solano often describes vertical gardens as “biofilters” because they help clean polluted city air. Plants absorb carbon dioxide while trapping dust and airborne pollutants from traffic and industry.The gardens also create habitats for birds, bees and insects in places where traditional green spaces are limited. In crowded cities with little room for parks, living walls offer a way to bring biodiversity back into urban environments.According to Solano, carefully designed vertical gardens can produce significantly more oxygen than conventional ground-level green spaces because of their dense layers of vegetation.Creating a successful vertical garden involves much more than simply attaching plants to a wall. Designers must carefully choose plant species based on climate, sunlight, humidity, altitude and maintenance needs.A typical system includes waterproof membranes, structural supports, irrigation pipes and nutrient delivery systems. Modern versions are designed to use very little water while requiring minimal maintenance.Through his Alicante-based company Paisajismo Urbano, Solano has helped develop nearly one million square metres of vertical gardens around the world. Solano is also focused on making vertical garden technology accessible to ordinary people. Through training programmes run with his Guatemala City franchise, By Botanik, students learn everything from plant identification to irrigation systems and project management.The courses are designed for beginners, and Solano says people do not need to be botanists, architects or engineers to enter the field. According to him, most participants eventually go on to create real projects in their own cities.As climate change increases temperatures across major urban centres, vertical gardens are being viewed less as luxury architecture and more as practical environmental infrastructure.Unlike traditional parks, living walls can be added directly to existing buildings without requiring additional land. Old office towers, highways, apartment blocks and public structures can all potentially become green spaces.For Solano, the mission goes beyond aesthetics. By transforming blank concrete walls into living forests, he hopes cities can become cooler, healthier and more sustainable places to live in the future.