by Eoghan Connaughton
PgD. Environmental Protection; Msc. Environmental Science.
Gaelic Woodland Project – Founder
Local Authorities Water Programme- CWO & Researcher
An Taisce– Climate Ambassador
Miyawaki Method: Don’t count trees planted on day one.
The environmental situation in Ireland has created the hunger for an afforestation method that can rapidly replenish our forests for biodiversity and climate. Considering trees are slow-growing, the introduction of the Miyawaki Method, which presents remarkably rapid growth, is being presented as the solution. Although the Miyawaki Method of high-density tree planting was deemed exemplary at the 1992 Earth Summit and the UNESCO’s 1994 Biodiversity Congress in Paris, it is absolutely necessary to determine whether this method, which was developed in Asia, is suited to the Atlantic climate and Ireland’s arboristic supplychain quagmire. Fortunately, there has been a steady stream of publications since 1993 with long-term studies for us to consider before we champion this temporally established, yet spatially novel approach to tree planting in Ireland.
Dr Akira Miyawaki was born in 1928; he was a botanist who specialised in seed providence and developed a keen eye for the ecological composition of Japan’s ancient forests. He celebrated his ancestors’ principle of honouring this ecology through the cultivation of traditional sacred groves, or Chinju no Mori.
Miyawaki, inspired by the traditional practice of Chinju no Mori and encouraged by the scientific precedent of ‘potential natural vegetation’, established by his professor Reinhold Tüxen, developed what he called: “native forests by native trees” (Miyawaki, 1999). His seminal work included a ten-volume, 6,000-page study on phytosociological community units, or what he called “companion species”: this was a catalogue of plants that evolved and lived together in Japan, and would regenerate if human activity stopped indefinitely and climax succession was reached at once.
Miyawaki conducted “vegetation-ecological diagnosis” to generate plant associations, or potential vegetation maps, to inform planting regimes for his innovative afforestation technique. He wrote that these maps are “essential” and emphasised that “seeds must be collected locally, potted in soil associated with the planting site until the root network has established thoroughly within the pot” (Miyawaki, 1999).
To this end, Dr Miyawaki and his team collected 10 million seeds from ancient woodlands and sacred groves, which were meticulously catalogued by their geographical location and soil origin. Prior to planting in an area, he would establish a local nursery so the seeds could be propagated in soil associated with the site.
Between 1973 and 1998, Miyawaki was asked to plant 550 strategic forests across Japan; initially by corporations around newly built power stations and iron works, then by municipal departments for the creation of secure zones where the dense canopy could protect civilians from falling debris during earthquakes; then by the national government for forests along expressways and dams, and even buffer forests to both halt forest fires (Miyawaki, 1998) and to protect the coast from tsunami wave action (Miyawaki, 2014).
In the 1990s, Miyawaki was invited to trial his method for rainforest restoration in Malaysia and then for lowland tropical rainforest restoration in northern Brazil. Miyawaki generated a catalogue of plant companions for both regions; then his team collected local seed and germination until they had “fully developed root systems”: the process of cataloguing tropical companion plants and collecting seed took almost 2-years (Miyawaki, 1999). After Brazil, Miyawaki was asked to experiment with his methodology in Chile where he noted that the sites were not as successful due to overgrazing.
It is estimated that there are now over 3,000 Miyawaki forests established worldwide; the majority have been planted either in Japan (~1,400 forests) or in the tropics, but other sites include India, Italy, and now, Ireland.
There are ~27 research papers that attest to the efficacy of the Miyawaki method for enhanced biodiversity in usually urban, micro-forests. While some practitioners state the global database of Miyawaki planting is “well researched and validated” (Chawkew, 2022), these forests have only been planted in temperate Europe over the past 9-years, and there is no long-term study done in Ireland or the UK.
Furthermore, most research, conversation, and media have focused on the high survival rates of trees in the first years and rapid growth compared to traditional planting regimes; but these temporal observations are undermined by longterm studies which show that high-density planting will gradually lead to increasing mortality over-time as plants fight for space (Schirone, 2011; Sasaki, 2018; Brabandère, 2020).
The methodology was first tested in Europe in the 1990s in Sardinia: there was 61%-84% mortality of trees after 12-years (Schirone, 2011). Another site in Belgium has a 26% mortality rate after 6-years (Brabandère, 2020). This is a constant across long-term studies and a natural process as trees grow and begin to take up more space. Ideally, we should be planting for the future and not for the moment. If 10,000 trees are planted at high-density today, up to half may be dead in a decade.
This is an essential aspect of the Miyawaki Method that is being overlooked in Ireland and is subsequently a source of critique within the environmental science community. Charkow (2022a) notes that in the UK developers will need to satisfy Biodiversity Net Gain (BNG) targets and the Miyawaki Method presents an optimum solution by maximising tree planting within a small area. This offers economic prudence. It’s financially better to plant more trees over less land than have more land with less trees.
This being said, high-density planting wouldn’t be as great a concern if it weren’t for the limited tree propagation capacity on the island. Ireland currently has a strong reliance on importing trees from Europe due to the lack of nurseries here, which increases the risk of importing fungal and bacterial pathogens. There is precedent for this concern: due to a well-meaning forestry programme in 2007, which tried to incentivise the planting of native trees but inadvertently imported the Ash Dieback Disease and sent it to all corners of the island. This fungal pathogen was first reported in 2012; it’s now endemic and will likely lead to the death of most ash trees on the island.
Right now, a similar situation is happening with the fireblight: a bacterial pathogen that attacks hawthorn. If we continue importation of hawthorn we may inadvertently cause the death of hawthorn island-wide.
Miyawaki, who put such emphasis on the collection of seed from ancient woodlands and sacred groves, and the role that communities have as custodians for nature, would be shocked at our unconscious disregard for biosecurity.
Therefore, considering the recent adoption of the Miyawaki Method in Ireland, the fanfare attached, and the absence of any scientific research into its implementation here, this article hopes to inform responsible implementation considering the island’s ecological and logistical context to ensure that the methodology generated by Miyawaki doesn’t degrade in transit.
For example, when Shubhendu Sharma introduced the method to India in 2007 (and conducted a very successful TED Talk), he honoured the conditions set by Dr Miyawaki by collecting local seed for local propagation (Charkow, 2022). In contrast, the Miyawaki Method Handbook for Kent County Council doesn’t mention local seed collection and germination in pots for root development, rather it states that plants should be “bio-secure with stock produced within the UK”. There is no mention of potential natural vegetation for plant companionship, but advises “to plant as many different native species as possible for landscape restoration and biodiversity”. Publishers of the handbook note that they have no long term study to inform their recommendations.
To integrate this afforestation technique to Ireland in a way which honours the work of Akira Miyawaki, practitioners must adhere to the following fundamental principles established by Dr Miyawaki:
1. Generate a catalogue of Irish plant companions, or potential natural vegetation, suited to our unique ecology and temperate climate. Fortunately, there are plant catalogues associated with Ireland’s main forest types: Old Oak Woodland, Yew Woodland, Alluvial Woodland and Bog Woodland. Whatsmore, there is a register of Ancient Woodland Vascular Plants which are rare and need anthropogenic propagation and dispersal, such as aspen, pignut, and the strawberry tree, which only exist in Ancient Woodlands.
2. Practitioners of Miyawaki in Ireland must adhere to the method of collecting local seed; these seeds should be collected from the 183 surviving ancient woodlands catalogued by Perrin et al (2010). These often small and isolated woodlands contain the remnants of Ireland’s indigenous seed stock and are at-risk of desiccation and local extinctions. Practitioners could also collect seed from Heritage Hedgerows, which pre-date conventional hedgerows and are believed to be the remains of Ancient Woodland.
3. Seeds must germinate in soils associated with the planting site until their roots have fully developed in the confines of the pot- this process can take up-to 2 years. This creates the robust rhizome that supports bacterial and fungal communities, which increases soil fertility to support high-density planting. Bare root planting is incompatible with the Miyawaki Method.
4. As Miyawaki observed in Chile, forests planted in areas at-risk of overgrazing are vulnerable to total failure. In Ireland, deer overgrazing is a persistent high-impact pressure in all native woodland habitats (except yew woodlands). Therefore, Miyawaki forests in Ireland should be protected by deer fencing or individual poles- however, the latter is wasteful considering the high mortality rate.
There have been criticisms of the large time and energy input necessary for collecting and propagating seeds, but these are the principles that were established by Miyawaki (for very good reason), and if they’re not adhered to, it’s not a Miyawaki Forest. If planting is done with bare root trees, imported from abroad, then perhaps a better term for them would be Tiny Forest developed by Martin Crawford, or a Wee Forest as they’re known in Scotland. However, it is best to adhere to the approach outlined by Miyawaki for ecological and genetic integrity, and to build capacity in our indigenous nurseries for the intergenerational planting effort required to restore our ecological inheritance.
Regarding strategic planning, research shows that the method is very effective at binding soil on sloped sites and could be used to improve stability in areas at-risk of landslides. This is especially pertinent information considering the deluge experienced in the Cooley Mountains in November 2023 when riverbanks (and farmland) were washed away into Carlingford Lough. Planting adjacent to rivers can also protect watercourses from urban, industrial and agricultural pollution.
Lastly, as 76% of our Old Oak Woodlands are less than the necessary 25ha for ecological stability, new Miyawaki forests could be established adjacent to these sites to build resilience, or within a 10km radius for floral cross-pollination and avian migration.
There is a huge appetite for reforestation in Ireland which is something to be celebrated; however we must, as stewards of the shovels, ensure that this energy is directed into effective and responsible planting regimes and designs. The deforestation of Ireland took generations and it will take generations to restore. There is so much work to do that we must coordinate our efforts and harmonise our approach for maximum return on investment. We must not mark our success by the number of trees planted today if over half will be dead in a decade; we must make the effort and not settle for what is easy, we must do what is right.
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References:
• Dr.Rekha Mandowara (2022) MIYAWAKI FORESTS. Vol: 9, Issue 3; y, BBD GovernmentCollege, Chimanpura, Shahpura, India
• Charkow, M (2022) Forests for the Future. Science and Opinion. Avtree. [online] 29-81-section-prf3.pdf (avtree.co.uk) [23/04/24]
• Charkow, M (2022a) Why use the Miyawaki Method? Creating Biodiversity Within Forests. AVArboriculture. Article. [online] Why use the Miyawaki method? – Arbor Vitae Arboriculture Ltd (avtree.co.uk) [23/04/24]
• Qian, X, et al (2021) Digital Design Exploration of Nature-Approximating Urban Forest Basing on the Miyawaki Method: A Case Study of Xingtai Forest in a Hebei Green Expo Garden. Landscape Architecture Frontiers, 2021, Vol 9, Issue 6, p060. DOI: 10.15302/J-LAF-0-020015
• Daou, Alain and Saliba, Mansour and Kallab, Antoine. (2024) A Review of the Miyawaki Method. Available at SSRN: https://ssrn.com/abstract=4728239 or http://dx.doi.org/10.2139/ssrn.4728239
• Miyawaki Method Handbook By Louise Butfoy Kent County Council August 2023. [online] SOF-TOW_Miyawaki-Method-Handbook-KCC-Aug-23.pdf (treecouncil.org.uk) [24/04/24]
• Webber, S (2022) The Miyawaki Method for Making Forests. Creating Tomorrow’s Forests. Article.
• Miyawaki, A (1999) Creative Ecology: Restoration of Native Forests by Native Tree. Japanese Center for International Studies in Ecology (JISE) and Nagano Nature Conservation Research Institute (NACRI), Japan (Correspondence; Fax, 81-45- 651-7692; E-mai)
• Schirone, B., Salis, A., & Vessella, F. (2011). Effectiveness of the Miyawaki method in Mediterranean forest restoration programs. Landscape and Ecological Engineering, 7(1), 81-92. https://doi.org/10.1007/s11355-010-0117-0
• Miyawaki, A. (1993). Restoration of native forests from Japan to Malaysia. In: Lieth, H., 721 Lohmann, M. (eds) Restoration of Tropical Forest Ecosystems. Tasks for vegetation 722 science, vol 30. Springer, Dordrecht. https://doi.org/10.1007/978- 94-017-2896-6_1
• Miyawaki, A. (1998). Restoration of urban green environments based on the theories of 724 vegetation ecology. Ecological Engineering, 11(1-4), 157-165. 725 https://doi.org/10.1016/S0925-8574(98)00033-0
• Miyawaki, A. (2014). The Japanese and chinju-no-mori: Tsunami-protecting forest after the Great East Japan earthquake 2011. Phytocoenologia, 44(3-4), 235-244. https://doi.org/10.1127/0340-269X/2014/0044-0571
• Sasaki, T., Ishii, H., & Morimoto, Y. (2018). Evaluating restoration success of a 40- year-old urban forest in reference to mature natural forest. Urban Forestry & Urban Greening, 32, 123-132. https://doi.org/10.1016/j.ufug.2018.04.008
• Literature Review: delivery.php (ssrn.com)
• MORE:
–Miyawaki forests are a global sensation, but not everyone’s sold on them (mongabay.com)
–Report-on-studying-Miyawaki-forests-in-Belgium-060923.pdf (urbanforests.com)
