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Watercress watchers: securing wild food

Taranaki ākonga (students) are checking the health of local streams so that they can safeguard food of cultural importance.

Collecting samples

Rangatahi at Waitara High School have enlisted scientists and Māori knowledge holders to help them check the health of local streams known to be mahinga kai – culturally important places where wild foods like watercress have been harvested for generations.

Kowhitiwhiti – watercress – is an important food for Māori because it is used in many meals made traditionally. When manuhiri (guests) visit a marae they are usually fed with hua whenua (wild food) from local mahinga kai. This is an important element in upholding manaakitanga (hospitality, respect, caring for others) by tāngata whenua (locals).

These plants are also eaten as part of locals’ everyday diet: “We eat watercress at home - we collect it off the land on our farm," says 15-year-old student Kaedyn.

However, with increasing water pollution and decreasing habitats from recent changes in land use, the availability of these traditional foods are becoming a cause for concern.

Checking samples

To try and investigate, Donna Eriwata on behalf of Hapū o Ōtaraua joined forces with students at Waitara High School and scientists at BTW Company to set up a new research project looking at water and habitat quality at known sites with kowhitiwhiti and whether it is safe to eat.

The knowledge the rangatahi get from this work also helps them learn how to become kaitiaki (guardians) of these and other culturally important places for future sustainability.

In the project, the team are checking four different streams that each having different potential sources of pollution nearby, ranging from high-traffic roads to dairy farms.

The students are learning how to check the streams’ temperature, depth and flow speed, how clear the water is, the amount of dissolved oxygen in it (how ‘breathable’ it is), the concentrations of minerals in it, and the number of different types of wildlife that live there.

Monitoring an open stream

When the rangatahi checked the first two sites they noticed straightaway how different the streams are from each other; in both their physical appearance and in the wildlife they host.

Emma, 15, says that the second stream was more open and shallow, with more sunlight than the first stream they tested earlier.

“The other site is deeper and there are more snails, which shows the site is more polluted because the snails have lived longer than the insects,” Emma says.

"Snails are pollution tolerant, whereas insects are not, which together can give us a good picture of how healthy the water is," explains teacher Kirsten Keighley.

Daynena, 16, adds, "I counted the insects and can see that there are definitely more insects here than at the other site and this tells us that the water is cleaner."

Collecting samples

Sheridan Standen, an environmental scientist at BTW Company, says that the students have also worked out that the dissolved oxygen gets lower the further downstream they test for that, because the more rapid areas upstream ‘churn’ more air into the water.

Her colleague Greg Larkin adds that the best environments for watercress are indeed fast-flowing streams, but only if they get enough sunlight since too much shade can lower the water quality.

Kaedyn says he noticed that the second stream has better water flow, despite being muddier than the first site they tested.

“I liked doing the water sampling because it was really hands on,” he says.

His classmate, 13-year-old Eliath, adds, “I've really enjoyed doing this work with my friends. My favourite part was looking at the insects.”

Monitoring an open stream

After processing the water samples in the laboratory and working through the data, Greg at BTW reveals that all four of the tested sites contain unhealthy levels of bacteria in the water.

“Two of the four sites also had bacteria on the watercress, with one site having watercress bacteria at a level higher than the guideline safety threshold,” Greg says. “The bacteria comes from contaminated water joining the streams, but we don’t yet know the actual cause.” 

Fortunately, the other two sites’ watercress were found to be free of bacteria, so are safe to eat.

Hapū o Ōtaraua, BTW and Waitara High School are now setting up their own sustainable system for growing kowhitiwhiti in the school grounds, homes and marae.

“We will use the water and plant test results to establish a closed circuit system that can artificially create a good environment for growing kowhitiwhiti,” Donna says.

Counting insect diversity

About the project

Waitara High School logoBTW LogoKo Ngā Kowhitiwhiti is run by Hapū o Ōtaraua, BTW Company and Waitara High School, with support from the Taranaki Participatory Science Platform.


Participatory Science Platform

The Participatory Science Platform supports collaborative projects that bring together communities and scientists or technologists on research investigating a locally-important question or problem.

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