Book Extract

How to start a Mini-forest revolution

Can the Miyawaki Method rapidly rewild the world?

Want to learn how to turn asphalt into ecosystems to save the planet? Forest maker Hannah Lewis presents a unique approach to reforestation devised by Japanese botanist Akira Miyawaki

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Hannah Lewis

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Bundled up in a rain jacket and donning a wide-brimmed straw hat, Dr. Akira Miyawaki stood in front of thirty-two potted, twig-sized seedlings, each accompanied by an image of the mature tree it would one day become.

“I’m going to give you some of the thirty-two species’ names,” he explained to the employees of a Toyoda Gosei automotive parts plant in Lebanon, Kentucky. The trainees listened attentively. “It is very difficult to remember all thirty-two, but please try to remember three or four. This is an American beech,” Miyawaki said, passing around one of the young trees. He encouraged everyone to feel the seedling, to use all of their five senses to get to know this plant that would become an integral member of the forest community they were about to set in the ground.

This is an extract from Hannah Lewis’s new book Mini-Forest Revolution (Chelsea Green Publishing, September 2022) and is reprinted with permission from the publisher. it is the first-ever book about a movement to restore biodiversity in our cities and towns by transforming empty lots, backyards, and degraded land into mini-forests.

“The tree-planting we are going to do at Toyoda Gosei is not for the production of timber or the beautification of the area,” Miyawaki declared. “This project is for yourself – you as local community people – to protect your lives from disastrous situations.” For some, the statement may have seemed like a stretch. But Miyawaki had witnessed native trees and forests accomplish great feats, from withstanding earthquakes while the built infrastructure around them collapsed, to preventing the spread of fire, to blocking cars from drifting out to sea in the aftermath of a tsunami.

A few days later the newly trained leaders themselves led some 4,000 co-workers and community members in planting 35,000 trees and shrubs along the perimeter of the factory grounds. Within a few years the tiny seedlings they had once held in the palms of their hands would transform into a tall, dense band of forest between the manufacturing plant and surrounding warehouses and farmland. This thin strip of wildlife habitat in an otherwise industrially transformed landscape was meant to cushion the immediate area against extreme weather. It was one of thousands of natural forests planted globally according to the Miyawaki Method.

This technique, which allows for the creation of a mature natural forest in a comparatively small amount of time, is based on a careful calculation of the plant species that are best suited to the local environment. This is exciting in and of itself – a mature forest is a beautiful landscape element; a buffer against extreme heat, polluted air, flooding, and drought; an educational opportunity; and part of an antidote to the global climate crisis. But the Miyawaki Method is also exciting because it can be applied to areas of any size – a fact that has given rise to the term mini-forest to describe small dense woods taking root around the world in locations both urban and rural. Imagine turning an area as small as six parking spaces into a forest – it can be done! Calling such a tiny grove a “forest” refers to the natural structure and composition of the vegetation rather than the footprint. Indeed, a true forest is much larger. Yet the implications are radical: With enough dedication, anyone anywhere can involve their community in a process of rewilding depleted land, one small patch at a time.

Miyawaki developed the forest restoration method that bears his name in the 1970s, as Japan’s rapid postwar development was showing its downside in the form of pollution and deforestation. The young scientist understood something that is not necessarily obvious: that humans depend on functioning ecosystems for our well-being and survival.

Miyawaki developed the forest restoration method that bears his name in the 1970s, as Japan’s rapid postwar development was showing its downside in the form of pollution and deforestation. The young scientist understood something that is not necessarily obvious: that humans depend on functioning ecosystems for our well-being and survival.

“It is vegetation, especially forests with multiple, complex layers of various trees, that controls a wide range of environmental processes and conditions,” Miyawaki wrote in his 2006 book, The Healing Power of Forests, coauthored with American ecologist Elgene O. Box.

Forests cover about a quarter of Earth’s land surface, yet an estimated 82 percent of forests are degraded to varying extents as a result of industrial logging and other activities. They have lost at least part of their capacity to play their vital, protective roles. Though generally preferable to bare ground, vegetation varies in its ability to provide ecological services. Much of the greenery in cities and suburbs is a combination of trendy flowering plants, isolated trees, and ubiquitous lawn, the latter of which demands mowing and watering to maintain its carpet-like perfection. Crop monocultures dominate rural agricultural landscapes.

The plants we call weeds grow in all the in-between spaces, and as Miyawaki came to appreciate, they play a healing role on land, similar to that of a scab on skin. “In nature, land does not want to remain barren,” Miyawaki wrote. Yet weeds rarely have the chance to assemble into more complex, leafier communities because of ongoing trampling or clearing; the land they colonize remains sparsely covered. In contrast to single-layer vegetation like weedy patches or manicured lawns, forests are endowed with five to thirty times more green-surface area and are thus “much more effective at providing ecological services.”

The forest is the root of all life. It deepens our intelligence and increases our sensitivity as human beings.

Akira Miyawaki, botanist

Planting a forest is not the same as simply planting trees. We plant trees for many reasons: to produce commodities like wood, fruit, oil, or rubber; to decorate and shade yards, streets, and parks; and to block wind, stop erosion, or sequester carbon. Each use determines the species that are chosen and how those trees will be planted. For example, a timber plantation may resemble a natural forest from a distance, but up close, we can see a monotonous grid pattern. The goal is uniform, fast-growing, straight-trunked trees that are easy to access with large harvesting machines. Similarly, if we consider carbon sequestration as a singular goal, we may favor planting only a few fast-growing species to achieve a quick result.

So, what’s the problem with planting trees rather than planting forests?

To put it simply it is the interactions we cannot see that drive the ecological processes we value. The past few decades have seen a rousing surge in research illuminating some of these previously hidden interactions. “A forest is much more than what you see,” explains Suzanne Simard, whose pioneering research shows how underground fungal networks connect trees to one another, allowing them to communicate and share nutrients. These webs of exchange enable a forest “to behave as though it’s a single organism,” with a kind of intelligence. A natural forest is a community of coexisting, interacting organisms – trees, shrubs, moss, fungi, bacteria, insects, animals (including humans acting as equal members of the community) – that rely on one another for food, shelter, and other ingredients of life.

Interspecies interactions fortify the ecosystem as a whole. For example, mycorrhizal fungi – the fungi that form mutually beneficial relationships with plants’ root systems – enable plants to transfer carbon into the soil, where it may ultimately be stored for hundreds or thousands of years. These fungi also improve the soil’s structure, making it spongy and able to absorb abundant rainwater, some of which infiltrates farther into the ground to refill aquifers. A living soil rich in organic matter is critical to a forest’s ability to mitigate flooding and drought. But these vital relationships arise only when plants are allowed to grow and thrive in a natural community. When we plant individual trees or monoculture tree plantations, we miss out on many of the benefits that come from these webs of interdependency.

Just as planting a forest is an improvement on planting a grid of timber trees, planting a forest according to the Miyawaki Method ensures that the forest will be the best fit for its environment – more stable, more resistant to stress, and ultimately more successful.

Most people will never be able to take on a big ecosystem restoration project on the scale that is needed – they will not have the resources or the time. But small groups of people all around the world, in innumerable settings and circumstances, can plant a mini-forest. It is a revolutionary approach to planting trees, and it’s taking hold from India to the Netherlands and everywhere in between.

Most of us know the term old-growth forest, which refers to natural forests that are still mostly free of human disturbance (though not necessarily free of human presence). These forests have reached maturity and beyond – a process that often takes centuries. As a result, they host incredible biodiversity and sustain a complex array of ecosystem functions.

The Miyawaki Method is unique in that it re-creates the conditions for a mature natural forest to arise within decades rather than centuries. At the heart of the method is the identification of a combination of native plant species best suited to the specific conditions at any given planting site. As we’ll see, determining this combination of special plants is not always so straightforward.

More than just the species selection, the Miyawaki Method depends on a small collection of core techniques to ensure the success of each planting. These include improving the site’s soil quality and planting the trees densely to mimic a mature natural forest. It’s also necessary to lightly maintain the site over the first three years – which can include weeding and watering. Amazingly, though, if the simple guidelines are followed, after that point a Miyawaki-style forest is self-sustaining.

The trees grow quickly (as much as 3 ft [1 m] per year), survive at very high rates (upward of 90 percent), and sequester carbon more readily than single-species plantations. The Miyawaki Method is also special for its emphasis on engaging entire communities in the process of dreaming up and planting a forest. Whether you are three years old or eighty-three, chances are you can place a knee-high seedling into a small hole in the ground. At the very least you can appreciate and cherish the return of quasi-wilderness to a space that was once vacant.

Imagining a Mini-Forest’s Potential

The Miyawaki Method calls for planting native species, but not just any natives. In particular, the method involves a careful investigation of what’s known as potential natural vegetation (PNV). This unusual term refers to the hypothetical ecological potential of a piece of land. Or another way to say it is that potential natural vegetation is “the kind of natural vegetation that could become established if human impacts were completely removed from a site” over an extended period of time. A site’s PNV depends on many factors, including current climate conditions, soil, and topography.

Whether you are three-years-old or 83, chances are you can place a knee-high seedling into a small hole in the ground.

How is potential natural vegetation different from the plants we see growing around us in towns and cities? For starters, in almost all developed landscapes, many of the plants are not native to the area, and as such may require maintenance to survive or reproduce.

Given that most of Earth’s land surface is significantly altered by urbanization, agriculture, road construction, mining, and the like, it is far from obvious what the original vegetation of any given location would have been. (Original vegetation and potential natural vegetation are not necessarily exactly the same, but they are closely related.) Unraveling this mystery takes curiosity, patience, and persistence. However, thinking about land in terms of its potential natural vegetation is a powerful angle from which to approach ecosystem restoration, because it reveals which species and groups of species are best adapted to a particular environment and therefore more likely to thrive and to support a wider web of wildlife.

To arrive at the potential natural vegetation for a given site, it helps to understand the sequence in which plant communities develop.

Nature’s March

If left alone, previously forested land can grow back into mature forest via a process known as ecological succession, wherein the biological components of the ecosystem change over time as larger and longer-lived plant communities colonize the land. As mentioned, this process can take centuries to unfold. A foundational aspect of the Miyawaki Method is that it sidesteps the slow and capricious march of natural succession, instead focusing on those plants that mark the theoretical endpoint of succession.

In nature, the successional process begins when lightweight seeds drift in and germinate on bare ground. Hardy, fast-growing plants – what scientists call pioneer species – such as clover, plantain, and dandelion take advantage of ample sunlight and space. They live short lives, produce a lot of seeds, and shelter the ground in the process. Next to show up are larger perennial herbs and grasses, followed by shrubs and pioneer trees, such as birch, poplar, or pine.

“Each new group of species arrives because the environmental conditions, especially the soil, have been improved; each new species becomes established because it is more shade tolerant than the previous species and can grow up under their existing foliage,” Miyawaki wrote. He explains that just when a community of plants appears to be reaching its fullest potential, the seeds of the succeeding community are already germinating in its shade. The species making up each new successional stage tend to be bigger, more shade-tolerant, and longer living than those of the previous stage.

“The plant community and the physical environment continue to interact,” Miyawaki explained, “until the final community most appropriate for the environment comes into being, one that cannot be replaced by other plant types. In regions with sufficient precipitation and soil, the final community is a forest.”

Theoretically, this final community of plants, known as the climax community, is not easily superseded. Big trees that are considered climax species in their respective environments live for hundreds or thousands of years, forming canopies that shade the interior of the forest, keeping it cool and moist. Climax species shade out pioneer species and dominate the forest.

“In the absence of major environmental change, the climax is normally the strongest form of biological society and is stable in the sense that its dynamic changes are constrained within limits,” Miyawaki wrote. Partly on account of the microclimate they create, such ecosystems tend to be more resistant to external conditions, such as heat or drought.

In nature, we have all the allies we need in this struggle, if only we chose to acknowledge them as such.

Hannah Lewis

What might climax vegetation look like? There are generally a few different climax communities in a given landscape. Cottonwoods and willows might grow in a river valley while pines and firs populate the nearby mountain flanks. In flatter regions with moderately moist soils, the potential natural vegetation is evergreen or deciduous hardwood species such as laurel, oak, maple, or beech. Miyawaki forests have typically been planted in conditions like this. Not all of Earth’s biomes, on the other hand, are dense forest. Places like natural grasslands, desert scrub, and sand dunes, for example, have their own ecological value and should generally not be replaced by forest – Miyawaki Method or otherwise – except perhaps along their riparian corridors.

Making a Mini-Forest: The Basics

Rejuvenating the soil is one of the basics of creating a mini-forest on a degraded site. In fact, it’s the critical first step – the goal is to simulate the living soil of a healthy, mature forest. This happens naturally during the stages of ecological succession, but because the Miyawaki Method skips immediately to the climax stage, some preparation is required to compensate. In the absence of a loose soil with plenty of organic matter, trees will struggle to grow properly. In a Miyawaki forest project, the soil is typically recharged by decompacting and amending the site with organic materials.

Planting density is another signature of the Miyawaki Method. Conventional wisdom says that plants compete for light, water, and soil nutrients; therefore, plants should have lots of space between them to reduce that competition. But it’s not how a Miyawaki forest works. For a Miyawaki forest, the standard planting density is three plants per square meter. This density helps achieve the goal of ecosystem regeneration. After all, in a natural forest, plants are not evenly and widely spaced. Dense planting stimulates mutualistic and competitive interactions among the plants and facilitates connections with soil microorganisms. It also promotes virtuous competition for sunlight, hastening upward growth.

Mulching is a critical component of the Miyawaki Method. After planting, the ground is covered with a thick mulch similar to fallen leaves on a forest floor. Indeed, once the young trees have had a chance to mature, they will contribute leaf mulch to the forest floor naturally. Mulch protects the bare soil from water loss by evaporation, from erosion, and from temperature extremes. Mulch also suppresses weed growth and eventually decomposes into the soil, enriching it.

As they become established over the first few years, the plantings typically need occasional watering and weeding, but after three years the young forest patches are developed enough to shade out weeds and shelter the soil. They are then generally self-sufficient and need no maintenance of any sort – no pruning, no watering, no fertilizing, no pest control – ever.

In 2014, at the age of eighty-six, Miyawaki wrote: “I hope all of the Japanese people plant small saplings with their own hands in order to protect their own lives and those of their loved ones, and to preserve the lush verdure of Japan. I wish to spread the know-how and the results of this ecological reforestation to the whole world.”

In fact, the engaged botanist was already well on his way to this goal, having led forest-planting festivals in nearly three thousand locations in eighteen countries over the course of about five decades. Miyawaki was awarded the Blue Planet Prize in 2006 for his global leadership in tackling environmental problems, further spreading his message. Miyawaki’s partnership with Japanese industrial companies operating internationally was key to propagating the method widely enough for it be picked up by other groups in what would become the second wave of projects.

This new wave began in earnest in 2014 when the technique got a big internet-assisted booster. A young engineer who had discovered and fallen in love with the Miyawaki Method gave a TED Talk on the forest-planting approach, and the five-minute video became a global hit with well over a million views. Shubhendu Sharma worked at a Toyota plant in Bangalore, India, in 2009 when Miyawaki led a planting event there. Sharma volunteered to help plant and was fascinated to see how a natural forest could be assembled from its component parts – densely planted native shrubs, understory trees, and canopy trees re-creating the multiple layers of a functional forest.

The car company’s new grove grew vigorously. Impressed, Sharma dove into further research, immersing himself in the ecological concepts upon which the method rests. He planted a forest in his own backyard and observed its development. Nine months after taking root, the young forest had already attracted ten bird species that he had not previously spotted in his yard.

This experience reshaped Sharma’s understanding of forests and opened up a world of possibilities. Sharma had been happy working in automobile manufacturing. It was his dream job. But the Miyawaki Method tickled the same part of his mind that drew him to designing automobile assembly lines.

Sharma left Toyota in 2011 to launch the forest-planting company Afforestt, not because he had always wanted to become an entrepreneur, but because the Miyawaki Method was too good to keep secret. “I am an industrial engineer,” Sharma explained in his first major talk as founder of Afforestt. “The goal in my life has always been to make more and more products in less amount of time. So today we are making 100-year-old forests in just 10 years.” Starting a company “was a way of helping this methodology get a foot in the door of corporates and other institutions,” he told me when we spoke in 2020. “This is something everyone should know.”

The engineer wondered if he could put his professional training to work on the diffusion of what he considered an extremely effective system for forest regeneration. To that end, he drew up standard operating procedures (SOPs) for each step in the planting process: identifying the right combination of species, analyzing the soil, mapping out the planting site and workflow, preparing the site, planting, and following up with maintenance. He used these SOPs to train his staff and also made them available as an open-source material. Afforestt has since refined its training resources in the development of an eleven-part video series, which is available for free online (see resources, page 167).

In the first two years, Sharma managed to coax all of two people into signing up to have a mini-forest planted. By the third year, both the concept and the company promoting it were starting to catch on locally. Afforestt has since planted at least 138 forests in ten countries, while a growing number of new organizations and small businesses focused on Miyawaki-style mini-forests have sprouted up in in Europe, the Middle East, Africa, Australia, and North America (see resources, page 167, for a list of organizations).

Miyawaki often partnered with industrial leaders, planting what he termed environmental protection forests around factories, steelworks, wastewater treatment facilities, shopping centers, and power plants. He also worked with government ministries, cities, schools, and universities in Japan and abroad. By contrast, the new wave of projects is often community-driven, led by passionate, newly minted forest planters who have emerged from careers ranging from architecture and engineering to business administration and computer programming. These projects are also typically smaller than those Miyawaki took on, starting out as local experiments and often developing into larger programs as community stakeholders gain confidence in the approach.

While the Miyawaki Method is the guiding light for these fledgling organizations, following its somewhat complex prescriptions to a tee is easier said than done. This was especially true before detailed instructions on the method were available in English, which Afforestt had to create for itself.

In its early years, the Afforestt team mixed pioneer species in with climax species in an unwitting divergence from the Miyawaki Method. Fast-growing pioneer plants surpassed the climax species, which tolerate the shade but do not thrive in it. So instead of creating a climax forest directly as the Miyawaki Method is designed to do, mixing pioneer plants in with the climax species created an earlier successional community that slowed the growth of the climax species. Such a forest is biodiverse and ecologically beneficial in its own way, but it is not the Miyawaki Method.

The results spoke for themselves. In some cases, the pioneer species collapsed, creating empty pockets in the forests into which climax species eventually took hold. Once they learned, in 2016, that Miyawaki did not plant pioneer species in his forests, the company corrected course; they also started requiring an exhaustive forest survey before planting any forest.

Sharma has taken the technique that Miyawaki spread largely in person, shovel in hand, and carried it forward by sparking the imaginations of a generation coming to grips with the intertwining climate and biodiversity crises. The idea of restoring native ecosystems one tennis court–sized patch at a time is empowering, especially now when it is easy to feel helpless. Sharma’s pupils have themselves become the teachers, while their pupils, too, are becoming new teachers, spreading the technique and the ecological principles underlying it far and wide.

Regardless of the context, the people who assemble on a rainy or sunny Saturday to plant a native forest end up with their hands submerged in earthy soil. They finish the day having left a legacy whose growth they will be able to observe throughout their lives. And they are exposed to the tacit message that we are part of nature and as such have a role to play in its healing.

What’s so good about this?

Over Miyawaki’s long career, overconsumption in the Global North continued to the point that we have likely now overshot Earth’s ecological limits. Now, more than ever, we need solutions like the Miyawaki Method, which is witnessing a worldwide surge in popularity. We are seeing mini-forests springing up across the globe – from the backyard forest planted by tiny-forest champion Shubhendu Sharma in India to a young forest along the concrete alley of the Beirut River in Lebanon.

This is an edited extract from Hannah Lewis’s new book Mini Forest Revolution. If the ongoing climate crisis has left you unsure about the future of our planet, check it out for a much needed positive and inspiring read on how you can help.

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Meet the writer

Hannah Lewis is a writer who focuses on people, nature and conservation, and the editor of Compendium of Scientific and Practical Findings Supporting Eco-Restoration to Address Global Warming.

In Mini-Forest Revolution (Chelsea Green Publishing, June 2022), the forest maker explains how tiny forests as small as six parking spaces grow quickly and are much more biodiverse than those planted by conventional methods.