Between busy streets, parks and shopping centres, a green transformation is quietly underway,  bringing nature back to the urban sprawl of cities. Micro-forests, small areas of densely planted woodland trees, are being planted everywhere from London to Los Angeles.

But what are they and how can they make our built-up metropolises better?

What are micro-forests and why do we need them?

More than 420 million hectares of forest have been lost to other uses since 1990, according to the UN’s 2020 State of the World’s Forests Report.

With more than 85 per cent of the global population living in urban areas, micro-forests in cities offer an essential opportunity to combat deforestation.

The Miyawaki Forest Technique, invented by Japanese botanist and plant ecology expert Professor Akira Miyawaki in the 1970s, is the inspiration for micro-forests worldwide.

These diverse, organic small forests can be created on sites as small as nine square metres, and only use native species that would otherwise grow naturally in the planting area. They grow up to 10 times faster than monoculture forests, in just two to three decades.

Since Miyawaki’s work began, more than 280 micro-forests have been planted.

NGO Earthwatch Europe has planted 285 tiny forests since 2022. Their plots, made up of 600 trees, can attract more than 500 animal and plant species within the first three years. Locations include a sports ground and park in Haringey, North London. Meanwhile ‘SUGi’, a tree-planting programme which aims to restore biodiversity and reintroduce native species, has created 230 ‘pocket forests’ in 52 cities across the world, from Toulouse, France, to Saint George in Romania and Madrid, Spain.

How do micro-forests benefit the environment?

In polluted urban areas, micro-forests can help to restore soil, water and air quality, according to the Woodland Trust.

Their small size allows plantation in relatively limited urban space, often taking advantage of unused spaces such as school playgrounds, cemeteries, and near metro stations. They can also help to reduce the impact of heavy rainfall, and to keep towns and cities cooler.

Micro-forests can create more habitats for wildlife in cities, such as blackbirds or hedgehogs.  When planted in distinct layers, they can also develop plant communities of smaller shrubs and herbs, which allow the micro-forests to become self-sustaining after just three to five years of growth.

“Our pocket forests offer a myriad of benefits” says Elise Van Middelem, Founder and CEO of SUGi.

“Perhaps most importantly, they can support the positive well-being of communities. From a psychological perspective, interacting with nature reduces physical stress and can improve symptoms of mental ill health, including anxiety or depression.”

“They become magnets for human connection. People take respite during the heat of the day or visit to read a book; at other times the forest becomes a place of dancing, learning, discussion, and leisure. They are self-sustaining within 2-3 years from an ecological standpoint, but at a much deeper level, community members become stewards of the land itself.”

She adds: “They also positively impact children and youth. 140 of our pocket forests were planted in schools together with almost 80,000 children. Planting pocket forests provides children with a unique opportunity to engage with nature and see that their actions can have tangible environmental outcomes. Engaging the next generation with nature is critical, because in order for us to want to protect and care for nature, we need to feel a connection with it”

What are the challenges of planting in urban areas?

Despite the benefits of urban micro-forests, there are also issues involved in growing in cities.

Exposure to pollutants, high temperatures and drought can prevent deep root growth, and increase the likelihood of disease, according to Cities4Forests, a global alliance supporting nature in cities.

Van Middelem also highlights the challenge of gaining communities’ support in growing micro-forests: “It is necessary to effectively engage stakeholders in the community and get resident buy-in. A pocket forest cannot be planted without their approval”, she says. “However, none of these challenges are insurmountable.”

These are all issues that must be considered – but with time, micro-forests could help to reduce pollution in cities as well as making them more pleasant places to live.