INTERNETOFNATURE
Trees on top REWILDING ROOFTOPS WITH THE URBAN JUNGLE PROJECT
BY DR. NADINA GALLE “WELCOME TO THE JUNGLE,” Daan Grasveld says with a grin, steadying the wobbly ladder as I climb the final rung. What greets me is an unexpected sight: a meadow of wildflowers in full bloom, the hum of busy bees and seven full-sized trees swaying gently in the breeze. At first glance, it might look like an ordinary Amsterdam park — but then I remember: we’re five stories above the ground. The telltale sign? The treetops of the cypresses at street level just barely peek over the roof's edge. This isn’t just a green roof — it’s a living example of modern-day rewilding. In 2020, Grasveld co-founded The Urban Jungle Project, transforming rooftops into vibrant ecosystems that challenge our perceptions of underutilized space. “It all started with a heat problem,” Grasveld explains as we walk along the rooftop. “Residents of VvE Blueland were facing unbearable temperatures on the top floors. They wanted to install air conditioning, but some suggested turning this unused gravel roof into something greener.” VvE Blueland is a homeowner’s association managing a modern apartment complex in Amsterdam’s Oost district.
vegetation — 10,000 plants in total — chosen for their ability to thrive in limited soil and attract pollinators like bees and butterflies. The result? A dynamic rooftop ecosystem that buffers 38,000 litres of rainwater, reduces heat stress and provides shade and cooling for the surrounding urban environment. The urban trees are a standout feature. Suspended in modular frames, they are sustained by advanced irrigation systems that deliver water and nutrients directly to their roots with precision. Integrated sensors continuously monitor soil moisture, temperature and nutrient levels, relaying data to a central system that dynamically adjusts irrigation and fertilization in real time. “In the future, we aim to implement a closed-loop system,” Grasveld explains. “Water will drip onto the root ball, with any excess captured, recycled and reused — maximizing efficiency and minimizing waste.” Despite its successes, Grasveld admits a missed opportunity: “We didn’t take baseline temperature measurements before installing the green roof,” he acknowledges. “But the residents' stories speak for themselves. Three summers have passed since installation, and no one has brought up air conditioning again at
Constructed in 2008, the building houses 50 apartments and boasts a 650-square- metre flat rooftop. Once covered in gravel, its potential as a green space became clear during the pandemic, as residents began exploring ways to address heat stress. “Was it an easy sell?” I ask, imagining the logistical hurdles. Grasveld laughs. “Not at first. The roof had a weight limit of just 230 kilograms per square metre, so traditional solutions were out of the question. But we specialize in lightweight, modular green roofs, so we proposed an ambitious idea: what if we could create a real ecosystem here, complete with trees?” Together with partners like Rooftop Revolution and the Nationale Bomenbank, The Urban Jungle Project replaced the gravel roof with 2,321 plant crates and seven innovative “Urban Trees.” These trees are suspended in cube-like structures designed to evenly distribute their weight while providing essential nutrients and stability that traditional soil would. “Normally, a tree in the ground weighs 16,000 kilograms. With our root ball, we bring that down to just 450 kilograms,” says Grasveld. Each plant crate contains carefully selected
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