Many Indigenous knowledge systems understand that people who interact with plants for millennia often have an important role to play in promoting their abundance, often through mutualistic mechanisms such as seed dispersal. Despite this knowledge, there has been very little attention paid toward collecting quantitative data on plant distributions to document this role, especially when it involves people who do not engage in what we think of as agriculture—people who traditionally hunt and gather non-domesticated resources. This information is critical if we are to better understand the processes that lead to species declines and extinctions. In a recent paper, we draw on longstanding ecological, anthropological, and archaeological work with Martu peoples of the Great and Little Sandy Deserts of Australia to ask how the long history of Martu interaction with culturally important ‘wild’ food plants has shaped their abundance and distribution.
Martu have lived in the Western Deserts for at least the last 48,000 years, thriving (until colonization) on a highly mobile residential pattern centered around hunting and gathering. Until the mid-1960s, Martu maintained a network of more than 1000 major and peripheral residential sites centered on water sources and ritual places. These sites were embedded within Dreaming pathways that connected vast tracts of the Western Desert and were often rendered and remembered through song.
Spatially explicit Martu water source network. Nodes are linked to their nearest neighbors via a Delaunay triangulation. Image©Rebecca Bird.
While Martu were highly mobile, spending only months at most at a campsite, people returned to the same places time and time again to target abundant key plant species, such as bush tomatoes, other fruits, geophytes, grass and tree seeds, and animal foods, such as monitor lizards and macropods. During the cooler months, the landscape was fired en-route to and around sites in mosaic configurations radiating out from the central habitation area. The collection and processing of foods back at home bases (rather than at spatially random spots on the landscape) was viewed as both an ecological and social imperative: ecologically, the cumulative discard of propagules from processing plants would increase food availability near camp, and socially, large harvests consumed communally could create social solidarity and contribute to the hunter’s status as a generous person.
Three Martu women come together at a temporary camp to socialize around the fire after a hunting trip. Processing residues (a scatter of black seeds in front of each woman) locate where the bitter and inedible parts of Solanum diversiflorum (bush tomato) fruit have been cleaned out. Cleaned fruit are cooking in the coals, while the women wait to roast their harvest of parnajarlpa, monitor lizards (right). Photo used with permission from senior Martu estate holders©Rebecca Bird.
In the mid-1960’s, the last nomadic Martu families left the desert, returning twenty years later during Australia’s Outstation movement to hunt and gather across their traditional Country. Archaeologist Peter Veth was present when they returned, working with Martu on archaeological excavations and ethnobotany with colleague Fiona Walsh1,2. After their twenty-year absence, Martu were concerned about the decline and extinction of many plants and animals and the lack of fire in the landscape. They expressed the fear that the interruption of their foraging practices and other rituals to ensure fertility had caused plants and animals to disappear. In their eyes, Martu belong to Country and have an important role to play in its maintenance3, but such a perspective that links the well-being of nature to human intervention is at odds with the way most of us might think about how people interact with other species.
Ecological anthropologists Douglas Bird and Rebecca Bliege Bird joined the work with Martu in the early 2000s and have shown that the positive role Martu play is linked to burning: hunting fires are important for sustaining the plants and animals that people rely on4–6. Martu (and many other Aboriginal populations) have long used fire to burn grasses and undergrowth to expose small animal burrows or drive animals for mass capture. Aboriginal burning differs from lightning fires: it is often conducted during cooler winter months when winds are consistent, and when fires are smaller and more easily controlled7,8. By burning frequently and in small areas, Martu create a patchy fire mosaic with high vegetation structure and species composition diversity9,10, which provides access to both food and refuge for animals like wallabies and monitor lizards, staple food animals for Martu hunters. While it’s clear that fire does increase plant diversity at a landscape scale, we had not yet investigated whether or how it might affect plants, and which plants might respond to aspects of Martu fire regimes. Martu say they are important for plants, but what is the mechanism, and is it visible ecologically?
Theo Taylor burns a fire line for hunting parnajarlpa, sand monitor lizards (Varanus gouldii). Photo used with permission from senior Martu estate holders©Rebecca Bird.
Working separately, botanist Chris Martine has long been puzzled by the fact that edible desert Solanums in Australia (bush tomatoes) seem to be widespread yet have few extant seed dispersers11. Researchers have long suspected that desert peoples influenced the distribution of bush tomatoes and this has often been proposed as an explanation for the wide ranges of a handful of species such as Solanum chippendalei, S. succosum, and S. ellipticum12,13. Meanwhile, a number of related species considered inedible (or at least undesirable) are more narrowly distributed and appear to be contracting in range14.
Solanum diversiflorum (bush tomato) fruit. Photo ©Rebecca Bird.
In our recent work, we draw on our collective expertise to investigate the effects of Martu seed dispersal and fire on four native plants:jinjiwirri (bush raisin – Solanum centrale), wamula (bush tomato – Solanum diversiflorum), kunuruntu (woolybutt grass – Eragrostis eriopoda), and kipara mayi (fanflower – Scaevola parvifolia). We chose these four plants because each has a different potential for human dispersal: wamula seeds are bitter and inedible, scraped out before consumption as people sit around the fire; kunuruntu seeds are small and easily lost while winnowing; jinjiwirri seeds are edible and consumed, making them less likely to be dispersed by people, and kipara mayi are not actively targeted in foraging.
A young S. diversiflorum plant (upper right) emerges in the charcoal of a 3-year old Martu hearth fire after a dispersal event. An older, dead plant is visible in the center of the charcoal scatter. Photo©Rebecca Bird.
Drawing on an extensive ecological transect survey, we show that Martu burning is important for bush raisins (S. centrale), but for warmula (S. diversiflorum) fire is less important, and people seem to play a different role: that of seed disperser. On Martu Country, bush tomato patches are more likely to be found near old habitation sites, permanent water sources, and in landscapes that have been heavily used for hunting and gathering over the last 30 years. This relationship is not due to people simply moving to where plants are more abundant: we also surveyed several recently used camps where fruit had been cleaned around a hearth and found that many of them hosted new plants that weren’t there before people scattered seed. This effect is still visible at sites that have not been used since colonization and persists where Martu people still gather plants and transport their fruit (and seeds) across the landscape. This dispersal can be very long distances today, as Martu often collect large amounts in buckets and transport whole fruits by vehicle to other communities several hundred kilometers distant to share with friends and family.
Predicted values of plant presence by distance to nearest residential/archaeological site (at high and low land use), intensity of contemporary land use (at permanent and ephemeral water), time since fire diversity (by season of most recent fire), and fire frequency (by season of most recent fire). Predictor variables are standardized such that a value of 1 equals 2 standard deviations. Shaded error bands indicate 95% confidence intervals for the predicted value.
People also influence the distribution and abundance of kunuruntu. Eragrostis grasses were used extensively throughout the Australian deserts until colonization but are rarely used today. Kunuruntu seeds are labor intensive and require foragers to spend hours stripping seeds, threshing, and winnowing the seed before it can be ground into flour and mixed with water to make bread. Prior to colonization, women would collect large amounts of kunuruntu seed in wooden dishes, carry it to a flat termite bed near camp, thresh the seed with a round hand stone, and let the wind blow away the seed husks. Once the seed was released from the husk, it would be winnowed in wooden trays to separate the husk and sand from the seed, which resulted in many lost seeds near processing sites. Even though people rarely collect kunuruntu seeds today, the effects of past processing are still visible, with kunuruntu more likely to be found near old habitation sites.
Two Martu women (J. Biljabu and R. Williams) thresh Eragrostis eriopoda (kunuruntu, or woolybutt) seed prior to winnowing. Photo used with permission from senior Martu estate holders©Rebecca Bird
Most landscapes on Earth are shaped by long histories of human entanglement, including meadows and grasslands in Europe15, Japan16, and central United States17, and forests of the Pacific Northwest United States18. Recognizing the important role of Indigenous peoples in these ecosystems, particularly in the dispersal and abundance of putatively wild plants, thus has critical significance for a wide range of conservation issues. For example, the decline and extinction of some native species could be linked not to overuse, but to the disruption (or complete loss) of human-plant mutualistic interactions mediated for millennia by Indigenous practice. Understanding the mechanisms through which species and landscapes are maintained, whether through fire, seed dispersal, or other disturbance, is critical to the design of better policy and the application of best practices for the recovery and persistence of at-risk biodiversity19.
For more information on our bush tomato project, check out the podcast linked below!
Veth, P. M. Islands in the Interior: The Dynamics of Prehistoric Adaptations within the Arid Zone of Australia. (International Monographs in Prehistory, Ann Arbor, MI, 1993).
Walsh, F. J. & Veth, P. M. The influence of the spatial and temporal distribution of plant food resources on traditional Martujarra subsistence strategies. Australian Archaeology 88–101 (1987).
Walsh, F. To Hunt and to Hold: Martu Aboriginal People’s Uses and Knowledge of Their Country, with Implications for Co-management in Karlamilyi (Rudall River) National Park and the Great Sandy Desert, Western Australia. (University of Western Australia, 2008).
Bliege BIrd, R., Tayor, N., Codding, B. F. & Bird, D. W. Niche construction and Dreaming logic: aboriginal patch mosaic burning and varanid lizards (Varanus gouldii) in Australia. Proceedings of the Royal Society B: Biological Sciences 280, 20132297 (2013).
Bliege Bird, R. et al. Aboriginal burning promotes fine-scale pyrodiversity and native predators in Australia’s Western Desert. Biological Conservation 219, 110–118 (2018).
Bliege Bird, R. et al. Fire mosaics and habitat choice in nomadic foragers. Proceedings of the National Academy of Sciences 117, 12904–12914 (2020).
Bliege Bird, R., Codding, B. F., Kauhanen, P. G. & Bird, D. W. Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands. Proceedings of the National Academy of Sciences 109, 10287–10292 (2012).
Bliege Bird, R., Bird, D. W. & Codding, B. F. People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands. Phil. Trans. R. Soc. B 371, 20150343 (2016).
Greenwood, L., Bliege Bird, R. & Nimmo, D. Indigenous burning shapes the structure of visible and invisible fire mosaics. Landsc Ecol 37, 811–827 (2022).
Greenwood, L. et al. Indigenous pyrodiversity promotes plant diversity. Biological Conservation 291, 110479 (2024).
Martine, C. T. et al. Phylogeny of the Australian Solanum dioicum group using seven nuclear genes, with consideration of Symon’s fruit and seed dispersal hypotheses. PLoS One 14, e0207564 (2019).
Symon, D. E. A revision of the genus Solanum in Australia. Journal of the Adelaide Botanic Gardens 4, 1–367 (1981).
Bean, A. R. & Albrecht, D. E. Solanum succosum A.R.Bean & Albr. (Solanaceae), a new species allied to S. chippendalei Symon. Austrobaileya 7, 669–675 (2008).
Cantley, J. T. et al. A Foundational Population Genetics Investigation of the Sexual Systems of Solanum (Solanaceae) in the Australian Monsoon Tropics Suggests Dioecious Taxa May Benefit from Increased Genetic Admixture via Obligate Outcrossing. Plants 12, 2200 (2023).
Auffret, A. G. Can seed dispersal by human activity play a useful role for the conservation of European grasslands? Applied Vegetation Science 14, 291–303 (2011).
Miyanaga, K. & Shimada, D. ‘The tragedy of the commons’ by underuse: Toward a conceptual framework based on ecosystem services and satoyama perspective. International Journal of the Commons 12, 332–351 (2018).
Mueller, N. G. Indigenous People Prevented Climate-Induced Ecological Change for Millennia: Evidence from the Prairie Peninsula and Fire-Loving Forests of Eastern North America. in Climatic and Ecological Change in the Americas (Routledge, 2023).
Armstrong, C. G. et al. Historical ecology of forest garden management in Laxyuubm Ts’msyen and beyond. Ecosystems and People 19, 2160823 (2023).
Martine, C.T., P. Frederick and T. Kramer (Producers). 2023. Plants are Cool, Too! Episode 13: Wamula: How one Aboriginal community is making things better for an important plant. https://www.youtube.com/watch?v=IEBezHmsRRo