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Traditional Knowledge Suggests Fire Retardant Vegetation Can Help Mitigate Fire Risk

Authors: François Tron, Elodie Wanguene, Cédric Haverkamp, Régis Duffieux, Fabrice Poéda, Jean-Jacques Villegente, Thibaut Bizien, Anne Ganteaume

The fire-retardant characteristics of low flammable plant species, widely known from New Caledonian traditional societies, could contribute under certain conditions to the mitigation of fire risk and thus strengthen climate resilience.

As the new year is starting, a visit is due to the chief and friends of the tribe of Paana, at the foothill of Mount Panié, the highest mountain of New Caledonia. After a collective dinner at the community hall, we are chatting around the fire. Last year was particularly dry, with many fires blackening the mountains around the tribe, fueling conversations: “We can see the fire often stopped by small forest remnants along tiny creeks running down the mountains… What are these trees that are blocking fire?” The answer is straightforward: «Bourao is the main one and there are others».

In the context of climate change, particularly the intensification of drought periods (Dutheil 2019), the mobilization of traditional knowledge offers a significant opportunity for fire risk mitigation; it can thus be considered as a strategic climate resilience measure and nature-based solution.

New Caledonia is the world's smallest biodiversity hotspot with the highest density of endemic plants in the world (75% of the 3,400+ native plant species are endemic, according to FLORICAL (Morat et al. 2012 ; Munzinger et al. 2021) and the world largest lagoon, listed as a World Heritage Site. Ecosystem services associated with forests (freshwater provision, climate regulation, erosion control, non-timber forest products provision, cultural services, etc...) significantly contribute to the well-being of rural communities. With a land mass of 18,000 sq km, the interactions between the sea, freshwater bodies, and land is critical, both ecologically and culturally—the health of forests and mountains has direct effects on the condition of water and rivers, river mouths, coral reefs and the lagoon as a whole, and in fine the well-being and livelihood of the local populations.

While fire is associated with many uses and practices, largely disturbed since colonization and the introduction of many invasive species (Toussaint, 2018), most fires are human-caused (OEIL, 2021). Each year, human-caused bushfires burn 0.5 to 2% of the country (OEIL 2021) and up to 0.5% per year of the forest cover, with an increasing trend (Global Forest Watch, Vieilledent and al. 2021). Fire is also the most prominent threat identified by the IUCN Red List authority in New Caledonia, affecting 71% of threatened plant species (Endemia 2021). Moreover, forest cover degradation by fire is followed by soil erosion (Fig. 1), impacting rivers and marine ecosystems, with direct and indirect effects on biodiversity and associated ecosystem services and the well-being of local populations that depend on them. Material and economic damages from fires can be significant; loss of human life has even been reported.

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Fig. 1: The degradation of the vegetation cover by uncontrolled bushfires contributes to soil erosion, favoring landslides, sometimes deadly as shown here in Houailou. ©Conservation International / Photo by François Tron

Even if the fire is formally regulated, violations are rarely sanctioned, as this punitive approach is considered by public authorities and the justice system as a lower priority in our societal context, which explains the numerous ignitions. Customary and neighborhood fire management rules and sanctions exist in some places and sometimes implemented, however hindered by the numerous fire ignitions, fueling tensions and conflicts driving to fatalism. Moreover, the regular awareness-raising campaigns, essentially based on a moralizing approach (“fire is bad”), are considered to be ineffective or even inappropriate (Toussaint, 2018). In some occasions, local communities undertake reforestation projects to “repair the damage”, hoping for a reduction in fire use; these actions rarely take into account the fire regime nor the flammability of planted species. On the 10 sites where the Northern Province has supported local community tree planting over the past 12 years, 39% of the planted areas have been burned at least once (Conservation International, 2021). Innovative mitigation approaches are therefore needed.

The mobilization of traditional knowledge associated with fire retardant vegetation offers an important potential. From an informal spontaneous conversation, numerous traditional communities throughout the territory have confirmed the traditional empirical knowledge that “Bourao does not burn well; the fire hardly goes through; often the fire stops at its foot; other species have similar fire-retardant characteristic, etc.”.

The fire-retardant attribute of the vegetation is mostly related to a lower flammability than its environment, reducing direct fire propagation risk. Indirect effects of these species are important on local vegetation composition and environment conditions such as lower temperature and higher humidity on the ground (Murray et al 2020).

The vegetation flammability can be assessed through its ability to ignite and propagate fire. Specific flammability depends on the leaf morphological features, the dead fuel proportion in the plant, the leaf chemical content (water and other organic components) and the litter density, for instance (Ganteaume et al. 2011; Ganteaume et al. 2013; Romero et al. 2019).

The Bourao can therefore be described as fire-retardant (Fig. 2):

  • Empirical observations systematically demonstrate that Bourao’s leaves and twigs may desiccate during a grassland fire (which are low intensity and rapid fires) but hardly burn. This low flammability significantly reduces the risk of direct fire propagation.

  • Its wide and dense canopy reduces the soil dryness and prevents the formation of herbaceous vegetation creating a ground fuel break mitigating surface fire propagation.

  • Its dense and relatively high canopy (frequently more than 4 meters, and up to 8 meters) reduces heat radiation and intercepts glowing or flaming vegetation particles that are generated during a fire (i.e. barrier effect on firebrands; Ganteaume 2018). Its smooth bark does not desquamate, avoiding firebrand generation during a fire. These characteristics further reduce the risk of fire propagation.


Fig. 2: This bushfire hits a Bourao dense bush, which shows to be less flammable; indeed the fire did not go through this Bourao bush, which did not burn but only desiccate on its edge. © Conservation International / Photo by François Tron

The Bourao is fairly abundant in inhabited socio-ecosystems that also concentrate fire ignitions (OEIL 2021), therefore consolidating the socio-ecological relevance of planting Bourao as green firebreaks in those strategic areas. This species also has multiple traditional uses that could feed nature-based solutions to adapt to climate change. Indeed, its canopy provides shade, wind and marine spray breaks, its root systems stabilizes coastlines and river banks, etc. Other traditional uses include fibers for rope making, poles for field fencing, food and culinary ingredient, timber for construction and sculpture, etc.

The Bourao is easily propagated using direct cuttings, which is an important feature for a simple community action, easy to perform and cheap (Fig. 3). It is therefore conceivable for local communities to engage in constructive and positive small projects, supporting fire risk mitigation.


Fig. 3: A 5-months-old Bourao cutting in the Vallée de La Coulée, prepared by the Ville du Mont Dore and planted by the Red Ground Association on ultramafic soil at the exact spot where two large historic fires ignited in 2005 and 2019. ©Conservation International / Photo by François Tron

Other plant species with similar fire-retardant characteristics (Crossostylis sp, Geissois sp, Acalypha sp, Ficus cf habrophylla, Mangifera indica, etc.) have been identified by local communities for their potential effectiveness in green firebreaks to mitigate fire risk; all have traditional uses and indirect benefits, also supporting their social acceptability.

While several elders have suggested, “this may be why so many Bouraos grow around our crop fields; elders may have planted them there for this purpose too…”, this traditional knowledge is not accompanied by widespread and current know-how to plant fire-retardant tree species in green firebreak to mitigate fire risk. Specific efforts must be considered to move from empirical observation, localized historical plantations and pilot projects to wide-scale action for significant impact.

Emerging pilot projects, led in 2021 by Conservation International with local communities with the support of their public and customary authorities, suggest that this solution is relevant and acceptable. Two enabling conditions seem necessary to consolidate the approach, engage a broader support base and ultimately produce a tangible impact:

  • To demonstrate the effectiveness of this solution, including its limitations, requires the support of modern science.

  • To identify a sound dissemination strategy requires the engagement of appropriate and effective learning networks, especially those in the areas of fire risk mitigation and traditional knowledge.

Planting fire-retardant species in green firebreaks will not directly prevent people to light fires; it is neither the intention to cover large-scale degraded land with fire-retardant species. Still, this nature-based solution, grounded in traditional knowledge and multiple traditional uses, may be an accessible and culturally relevant opportunity for any community to be tangibly engaged in fire risk mitigation, thus reducing the impact of unintentional fires. It may also have an impact on individual and collective behaviors beyond areas planted as individuals and groups can now undertake practical activities along their vision for their place, move away from fatalism and anger and possibly engage on sensitive and productive discussions about fire. Ultimately, this nature-based solution can help local communities be more resilient to climate change and potentially contribute to large-scale restoration and regeneration efforts, and therefore create activities in rural areas (Fig. 4). This will nurture the connection between people and nature and contribute to the transmission of traditional knowledge.

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Fig. 4: The modest scale of green firebreak plantations makes it accessible to local communities and people, including volunteers, kids and women. © Conservation International / Photo by Cédric Haverkamp

In this perspective, it is critical to mobilize the support of traditional local customary authorities, locally elected officials and community leaders, including and noteworthily women.

“This traditional knowledge does not belong to any particular clan; it is a collective good that can be mobilized and shared for the benefit of all.” (JY Poedi, com pers).

Integrating traditional knowledge and perspective in land management strategies, especially those associated to fire-retardant species suggests a strong potential for nature-based solutions to help mitigate fire risk, build local community cohesion and strengthen climate resilience.

How to cite this page:

Bizien, T., Duffieux, R., Ganteaume, A., et al. (2021). Traditional Knowledge Suggests Fire Retardant Vegetation Can Help Mitigate Fire Risk. [online] Available at:


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