Reconstruction for restoration

A multidisciplinary project is using novel reconstruction technology and analysis to build a historical picture of Aotearoa’s lakes, with the hope of learning from the past to find solutions for the future.

Dr Andrew Rees
Dr Andrew Rees

Lakes380 is the aptly named project that is assessing past and present water quality across 380 New Zealand lakes. The carefully selected representative sample of New Zealand lakes will allow the team members to extrapolate their findings nationally. The project aims to prevent further predicted degradation and promote the restoration of New Zealand wai (water) through rohe (region) specific restoration options.

Dr Andrew Rees, based in Te Kura Tātai Aro Whenua—School of Geography, Environment and Earth Sciences at Te Herenga Waka—Victoria University of Wellington is a vital contributor to this project.

Dr Rees is leading research on lake sediment reconstruction. Using metre-long sedimentary cores extracted across the various lake sites, Dr Rees and his team are building trajectories of water quality from the past one thousand years—both before archaeological evidence humans arrived in New Zealand, and spanning the different land-use phases after their arrival.

“Lake sediments are natural archives. As things are washed into the lake, and things living in the lake settle, they build up an archive like pages in a book—each different layer is a page that tells the history of that local environment.

“Using this information, we can go back to before humans started modifying the landscape and see what properties may have showed resilience in lakes, and what promoted pristine water quality. This can help guide future restoration.”

Lakes380 sprang from a collective desire to restore New Zealand’s rapidly degrading wai health, and is now in its fifth and final year of research, moving a crucial step closer to the restoration of New Zealand wai.

The team at Lakes380 recognise that restoration will be primarily community-led, motivating them to place emphasis on taking a place-based approach, and on community inclusion.

“Science is heading slowly in the direction of community-based projects. With Lakes380 we’re developing these relationships so that we’re not just strangers coming in—we’re people who interact with the community and share our results to let them decide on a pathway that they want to take forward for restoring their sites,” says Dr Rees.

The recommendations made to each community will be tailored to individual water bodies based on the findings from this project.

Observations of when humans were first active on the landscape yielded particularly interesting findings. Early Māori burnt forests to create canopy openings which facilitated hunting and promoted bracken fern growth for food. This mobilised an increase in nutrients that theoretically should have driven nutrient flux or algal blooms within the lake.

Dr Rees explains that this is not represented in the sediment, which instead shows an increase in ground-dwelling plants around the lake. Opening of the canopy promoted the growth of these plants, which created a natural riparian zone—the vegetation strip growing around the lake margins—which acted as a buffer against material that would otherwise be carried into the lake by overland flow.

“A riparian zone was sufficient to mitigate any nutrients from the burning, and in some lakes, we even see that the water quality seemed to improve.”

Some site-specific recommendations have been made. For example, in Lake Wairarapa, where lake-bed ownership has been restored to Ngāti Kahungunu ki Wairarapa, evidence from lake sediment records shows that altering the hydrology to deepen the lake, or planting up the riparian zone with mānuka, could restore Lake Wairarapa from its turbid state.

The multidisciplinary nature of this project is allowing researchers to build a full historical picture in and around New Zealand lakes.

“Water quality is the main target of this project but there are indicators of environmental change as numerous as the mind is creative,” says Dr Rees.

Alongside the analysis of water health, researchers are looking to extract a whole host of data, from changes in climate and landscape, to the detection of introduced species and bird populations.

As the Lakes380 team looks to circulate their extensive findings and subsequent recommendations, Dr Rees hopes the project will support meaningful change.

“The ultimate goal is to get the science out of journal articles and university institutions, into plain language in the hands of the people. Arguably we don’t have to research climate change anymore, we know what’s going on, what we need to do is convince people to alter behaviours.”