Tiny forests yield big results: cleaner air, lower temperatures
The tiny forest lives atop an old landfill in Cambridge. Although it is still a baby, it’s already acting quite a bit older than its actual age, which is just shy of 2.
Its aspens are growing at twice the speed normally expected, with fragrant sumac and tulip trees racing to catch up. It has absorbed stormwater without washing out, suppressed many weeds and stayed lush throughout last year’s drought. The little forest managed all this because of its enriched soil and density, and despite its diminutive size: 1,400 native shrubs and saplings, thriving in an area roughly the size of a basketball court.
It is part of a sweeping movement that is transforming dusty highway shoulders, parking lots, schoolyards, and junkyards worldwide. Tiny forests have been planted across Europe, in Africa, throughout Asia, and in South America, Russia, and the Middle East. India has hundreds, and Japan, where it all began, has thousands.
Now tiny forests are slowly but steadily appearing in the United States. In recent years, they’ve been planted alongside a corrections facility on the Yakama reservation in Washington state, in Los Angeles’ Griffith Park, and in Cambridge, where the forest is one of the first of its kind in the Northeast.
“It’s just phenomenal,” Andrew Putnam, superintendent of urban forestry and landscapes for the city of Cambridge, said on a recent visit to the forest, which was planted in fall 2021 in Danehy Park, a green space built atop the former city landfill. As dragonflies and white butterflies floated about, Putnam noted that within a few years, many of the now 14-foot saplings would be as tall as telephone poles and the forest would be self-sufficient.
Healthy woodlands absorb carbon dioxide, clean the air, and provide for wildlife. But these tiny forests promise even more.
They can grow as quickly as 10 times the speed of conventional tree plantations, enabling them to support more birds, animals, and insects and to sequester more carbon, while requiring no weeding or watering after the first three years, their creators said.
Perhaps more important for urban areas, tiny forests can help lower temperatures in places where pavement, buildings, and concrete surfaces absorb and retain heat from the sun.
“This isn’t just a simple treeplanting method,” said Katherine Pakradouni, a native plant horticulturist who oversaw the forest planting in Griffith Park. “This is about a whole system of ecology that supports all manner of life, both above and below ground.”
The Griffith Park forest occupies 1,000 square feet and has drawn all manner of insects, lizards, birds, and ground squirrels, along with western toads that journeyed from the Los Angeles River, Pakradouni said.
Known variously as tiny forests, miniforests, pocket forests, and, in the United Kingdom, “wee” forests, they trace their lineage to Japanese botanist and plant ecologist Akira Miyawaki, who in 2006 won the Blue Planet Prize, considered the environmental equivalent of a Nobel award, for his method of creating fast-growing native forests.
Miyawaki, who died in 2021 at the age of 93, developed his technique in the 1970s, after observing that thickets of indigenous trees around Japan’s temples and shrines were healthier and more resilient than those in single-crop plantations or forests grown in the aftermath of logging.
He wanted to protect oldgrowth forests and encourage the planting of native species, arguing that they provided vital resilience amid climate change while also reconnecting people with nature.
“The forest is the root of all life; it is the womb that revives our biological instincts, that deepens our intelligence and increases our sensitivity as human beings,” he wrote.
Miyawaki’s prescription involves intense soil restoration and planting many native flora close together. Multiple layers are sown — from shrub to canopy — in a dense arrangement of about three to five plantings per square meter. The plants compete for resources as they race toward the sun, while underground bacteria and fungal communities thrive. Where a natural forest could take at least a century to mature, Miyawaki forests take just a few decades, proponents say.
Kazue Fujiwara, a longtime Miyawaki collaborator at Yokohama National University, said survival rates are between 85 percent and 90 percent in the first three years, and then, as the canopy grows, drop to 45 percent after 20 years, with dead trees falling and feeding the soil. The initial density is crucial to stimulating rapid growth, said Hannah Lewis, author of “MiniForest Revolution.” It quickly creates a canopy that shades out weeds and shelters the microclimate underneath from wind and direct sun, she said.
“A Miyawaki forest may be like a drop of rain falling into the ocean,” Fujiwara wrote in an email, “but if Miyawaki forests regenerated urban deserts and degraded areas around the world, it will create a river.”
“Doing nothing,” she added “is the most pointless thing.”