- Devised in the 1970s, the Miyawaki method has been a popular reforestation approach in urban areas worldwide.
- The method involves densely planting seedlings, which proponents say makes them grow more quickly as they compete for light.
- Proponents of the method claim that it enhances biodiversity, boosts carbon storage and results in rapid tree growth, among other benefits.
- However, a recently published review of scientific literature indicates the Miyawaki method may not be as effective as claimed.
The popular Miyawaki method of reforestation, often used to create “mini-forests” in urban areas, lacks empirical evidence to support its claimed benefits, according to a new study.
Proponents of the method have claimed rapid growth is achieved by soil improvement and dense planting, the latter of which causes saplings to complete for sunlight. The Miyawaki method has also been claimed to accelerate succession, enhance biodiversity, boost carbon sequestration, and increase tree density.
In the study, published in the Journal of Applied Ecology in December 2025, researchers reviewed 51 pieces of scientific literature on the Miyawaki method and found that only 41% provided quantitative assessments. Of these, only 33% included a control and a mere 14% included replication, key elements of the scientific method.
The Miyawaki method was first developed in the 1970s. However, over the past decade or so it has seen a new wave in international popularity, likely due to society placing greater importance on urban greening and reforestation, say two of the paper’s authors, Narkis S. Morales, a forest ecology researcher at the Bioeconomy Science Institute in Aotearoa New Zealand, and Ignacio C. Fernández, an associate professor of ecology and sustainability at the Adolfo Ibáñez University in Chile.
They see Miyawaki forests’ rapid growth rate as a major reason for the method’s popularity. People “don’t want to wait that much to have greener areas,” Fernández tells Mongabay.
However, the researchers caution that there may be social and ecological consequences for choosing any reforestation method — Miyawaki included — without evidence to first prove its efficacy.
‘Huge claims’
Originally developed by the late Japanese botanist Akira Miyawaki, the Miyawaki method was first used to establish fast-growing woods comprised of native plants around industrial sites in Japan, and later applied overseas in tropical forests as well. It has since become popular for urban greening projects around the world.
Fernández and Morales say they first became interested in the Miyawaki method after noticing various Miyawaki projects, some funded by the local government, around Santiago, Chile. They say they were surprised by the method’s “huge claims.”
“We started to wonder if this was a wise way to spend public money,” Fernández recalls, noting the relatively high costs of the method’s prescribed dense planting and soil improvement. They decided to conduct a literature review to see whether the method’s claims were backed by evidence.
Fernández, Morales and their co-authors write in their study that among the reviewed documents, the two most common claims about the Miyawaki method were that “it promotes rapid growth (up to ten times faster) and that the forest reaches maturity within a relatively short time span (20 to 30 years).” They found the former claim “partially supported,” while the latter had “null empirical evidence.”
The study also assessed claims about the Miyawaki method’s climate and ecological benefits, finding eight out of 51 of the papers they reviewed assert that the method increases carbon sequestration. However, only two papers actually estimated carbon stocks, and they “found no statistically significant differences compared to other methods over longer time periods.”
Morales and Fernández say they doubt carbon is a primary concern for many of the groups growing Miyawaki forests, given most projects’ small scale.
However, that may not always be the case. Reforestation expert Karen D. Holl, a professor at the University of California, Santa Cruz, in the U.S., who wasn’t involved with the study, told Mongabay that she has personally heard the Miyawaki method mentioned in meetings about tropical forest restoration strategies as a promising approach to enhance carbon and biodiversity. This despite the method being, in her view, “impractical and cost-prohibitive” at scale.
“I had never seen any rigorous data comparing the Miyawaki method with a control or other methodologies,” she notes. “I was pleased to see that Morales and colleagues did a rigorous review of the available literature and confirmed my hunch, namely that there are minimal rigorous studies demonstrating the ambitious claims of the Miyawaki method and that, in fact, it is an expensive restoration method.
“My work evaluating large-scale tree planting initiatives in the past few years suggests that the majority of organizations claim biodiversity, carbon, and livelihood benefits of whatever approach they are using, typically without much data to support the claims,” she adds. “It is important that all restoration methods be compared to a no-intervention control and/or other restoration methods at multiple sites to evaluate their efficacy in achieving stated restoration goals before they are promoted for widespread use.”
In their review, Morales and Fernández also found a difference between indexed and nonindexed articles. Being indexed — included in a searchable and often curated database — is generally seen as a marker of quality and academic rigor.
Only 54% of indexed articles they reviewed mentioned any claims about the Miyawaki method, compared to 73% of nonindexed ones. They also found that nonindexed articles contained on average 50% more claims.
“This pattern suggests that widely circulated claims about the Miyawaki method may originate primarily from grey literature,” the authors write, referring to documents that have not been produced by commercial publishers or peer-reviewed.
Although the researchers included non-English documents in their search, they did not use search strings in non-English languages, including Japanese. This, they acknowledge in the paper, “could have increased the number of documents included in our study.”
Undermining public trust, scientific knowledge
Morales, Fernández and their co-authors argue that “efforts to restore ecosystems — especially when taxpayer money is used — should take into account empirical evidence to ensure the efficient use of resources.”
They warn that a lack of data may erode public trust and support, noting to Mongabay that unsuccessful greening projects could be a “double punch” for disadvantaged urban communities, which tend to have less vegetation cover to start with.
Pushing a restoration method that lacks data also “undermines scientific knowledge” of proven methods tailored to specific ecological contexts, Morales adds.
“The effectiveness of the Miyawaki method — or other restoration strategies — may depend, at least in part, on which ecological processes dominate in each ecosystem,” their study states.
The pair says that in Mediterranean climate ecosystems like that around Santiago, with dry, hot summers and mild winters, plants collaborate rather than compete for resources. This contrasts with a key tenet of the Miyawaki method, which holds that plants will compete for resources.
“We are not against the Miyawaki method,” Fernández emphasizes. “But we are worried that a method that was designed for specific conditions is being applied everywhere.”
Banner image: Miyawai forest planting in New York, U.S. Image by NYS DEC via Flickr (CC BY-NC-ND 2.0).
Miyawaki forests are a global sensation, but not everyone’s sold on them
Citations:
Miyawaki, A. (1999). Creative ecology: Restoration of native forests by native trees. Plant Biotechnology, 16(1), 15-25. doi:10.5511/plantbiotechnology.16.15
Morales, N. S., Fernández, I. C., Durán, L., & Craven, D. (2026). Tiny forests, huge claims: The evidence gap behind the Miyawaki method for forest restoration. Journal of Applied Ecology, 63(1), e70242. doi:10.1111/1365-2664.70242
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