Building Invisible Walls: A Natural Approach to Conservation

In the eastern part of the island of São Miguel, in the Azores, lies the largest natural wall in the Iberian Peninsula. This wall, over nine metres high and 30 metres long, is an example of natural engineering, an approach that applies natural processes to construction. Natural engineering uses materials such as logs, stones, and native vegetation to create structures that work with ecosystems rather than against them. This approach was pioneered by SPEA, a Portuguese conservation organisation, in response to the challenges of restoring the Azores' native Laurissilva forest. The organisation faced difficult conditions, including unstable volcanic slopes, landslides, invasive plants, and streams damaged by intense rainfall. Traditionally, the solution would have been concrete, but concrete structures are not always suited for these dynamic landscapes. At Mata dos Bispos, the team created a living laboratory to test natural engineering techniques. They combined drainage systems with timber terraces, which slow the flow of water, trap sediment, and help prevent flash floods. ## The Benefits of Natural Engineering Natural engineering offers several benefits over traditional concrete structures. Water seeps through and drains away, rather than accumulating as it does in concrete. Even if an earthquake breaks the roots, they regenerate on their own. This approach has been used for 40 years in countries such as Switzerland, to prevent landslides and avalanches, or on Mount Etna in Italy. It has also been applied to river restoration, with more than 3 km of streams in the Azores already restored using natural engineering techniques. ## Collaboration and Innovation SPEA's experience and success with natural engineering are already recognised, and the team in the Azores has been commissioned to restore the two main springs supplying Vila Franca do Campo's public water supply, and to restore access to Lagoa do Congro. Natural engineering is also helping to tackle the effects of tourism. On popular trails, poor drainage creates muddy sections, and visitors often step off the path to avoid puddles, damaging fragile vegetation. The solution is to improve drainage so that staying on the trail becomes more appealing than leaving it. ## Ancient Roots, Modern Science Many of these practices have ancient roots, but the difference lies in combining ancestral knowledge with the data and calculations of modern science and engineering. Natural engineering is not suitable for every situation, and it requires collaboration between engineers, biologists, and agronomists. From restoring streams and peatlands to building almost invisible walls, SPEA's work shows that natural engineering can provide practical, resilient solutions inspired by nature. Like the ecosystems it supports, its greatest strength lies in something concrete cannot offer: the ability to grow stronger with time.