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Climate Change Threatens Māori Plant Use and Knowledge

Climate change will likely shift the distribution of culturally important plants in New Zealand, hampering harvests and putting long Māori traditions and knowledge at risk.

“Because of polluted water and soil, invasive species, and habitat destruction people are already having trouble finding the resources they need. Climate change adds another layer to this issue”, said Dr Priscilla Wehi from Manaaki Whenua – Landcare Research, who co-authored new forecast maps published in People and Nature (https://goo.gl/w7iB2k).

Local and indigenous people play critical roles in preserving biodiversity and ecosystems. Plants may expand or shift their range as global temperatures continue to rise, but ancient bio­cultural connections could be lost if plants become inaccessible to the people who use them. “Rather than just looking at whether climate change will make species go extinct, we wanted to know how climate change will affect people’s access to plants”, Wehi said.

The researchers focused on two plants that are traditionally used for weaving and as medicine, and that are important to the history and identity of the indigenous Māori people.

Kuta (Eleocharis sphacelata) is a soft, golden sedge found in wetlands across New Zealand and is especially valued in the North Island, where it is weaved into highly priced mats, hats and baskets. Weavers typically return to the same harvesting site each year.

The second plant species explored in this study, kūmarahou (Pomaderris kumeraho), is an endemic shrub that flourishes on well-drained clay soils in the northern regions of the North Island during winter. Māori people use it to treat respiratory ailments.

The team created maps of the plants’ current and future distribution under two climate change scenarios and compared these to known harvesting sites. They found that changes in temperature and rainfall patterns will likely have an impact on soil density in these wetlands. As a result, kuta may become less available in the far north of the country, where many of the weavers who use this plant live. Many of the current harvest sites have been used for generations.

“Weavers prefer to gather plants in their own tribal area, so this becomes an issue”, said study co-author Te Hemo Ata Henare of NorthTec. “There are alternative weaving plants available, but the colour, texture and quality of kuta are unique.”

Cultural currency is still practised among many tribes, with regional species such as kūmarahou ceremonially gifted or exchanged with people from other tribal regions. The forecast maps revealed that kūmarahou is likely to expand its range to the rest of the country as temperatures tend to become warmer, rather than shift or decrease as described for many other species. This could have an impact on tribal prestige and gifting practices.

Lead author Matthew Bond, a PhD student at the University of Hawai’i at Mānoa said: “Our results show that there are still places where the climate will be suitable for these plants to grow in the future. However, these plants will become less available in places where they are most valued for weaving and medicine. This means that although the species themselves are not threatened by climate change, the human knowledge, history and use of these plants are.”