Lakes380 – Our lakes’ health: past, present, future

Aotearoa is fortunate to have abundant freshwater systems. The New Zealand Ministry for the Environment reports the country has:

• 70 major awa (river) systems that run for more than 425,000 kilometres
• 249,776 hectares of repo (wetlands)
• more than 50,000 roto (lakes) of which around 3,800 are larger than 1 hectare.

As a nation, we value these systems. For Māori, tribal identity is linked to freshwater – each water body has its own mauri. The need to enhance and protect the mauri/health of our waterways is strongly felt, and an increasing amount of mahi is being done to address water quality issues for awa and repo.

However, there’s been a gap in our knowledge about the state of our roto. Ecologists are aware that many lakes have undergone changes, but they lack the data to know how and why the lakes have changed and how best to restore them. Lakes380 is a collaborative research programme that aims to fill those gaps.

The largest scientific study of lakes in Aotearoa

Lakes380 is the largest scientific study ever undertaken on lakes in Aotearoa. The programme, jointly led by GNS Science and Cawthron Institute, has sampled around 10% of the 3,800 lakes larger than 1 hectare. The project is underpinned by the whakataukī:

Me hoki whakamuri kia haere whakamua.

Current and future activity should be guided by lessons of the past.

An understanding of how and why lakes have changed over the past 1,000 years will help ecologists understand future changes and inform protection and restoration efforts.

Programme leaders Dr Marcus Vandergoes and Dr Susie Wood helped a team that selected the lakes for monitoring. Selection criteria included:

• geographic spread across Te Ika-a-Māui North Island, Te Waipounamu South Island and Rēkohu Wharekauri Chatham Islands
• altitude – a mix of coastal, lowland, highland and alpine areas
• the presence of non-native species
• catchment land cover.

The Lakes380 team also sought guidance from iwi to sample roto that are culturally significant – but not those that are wāhi tapu. The team also consulted with regional councils, the Department of Conservation and the Ministry for the Environment to ensure that lakes prioritised for restoration or protection were included.

A unique approach

The Lakes380 programme draws on both scientific and mātauranga Māori knowledge systems. While teams have been collecting and analysing water and sediment samples, they have also been working with iwi and hapū to understand and learn from their mātauranga and oral histories.

They’ve partnered with iwi in four locations to examine the cultural and environmental histories of significant roto:

• In partnership with Ngāti Kahungunu ki Wairarapa and Rangitāne o Wairarapa, the team produced the Wairarapa Moana Kete Pūrākau – a digital storytelling portal. This collection of stories comprises diverse personal memories, cultural knowledge and scientific information that enriches our understanding of lakes in this rohe.
• Working with Rangitīkei iwi, the team produced a documentary, Whakahokia te mauri o Oporoa, which weaves cultural knowledge and scientific data, allowing the story of Lake Oporoa and aspirations for its future to be heard.
• In partnership with Ngāti Koata and the Department of Conservation, the team developed a virtual reality experience for Lake Moawhitu (Rangitoto ki te Tonga D’Urville Island). This is informed by mātauranga Māori and science data, allowing viewers to see how the lake, landscape and human interactions have changed over 1,000 years.
• The team also produced Te Pātaka Kai o Tūwiriroa, a 30-minute film, in partnership with Te Rūnaka o Ōtākou. The film highlights the importance of a series of coastal lakes to Kāi Tahu and focuses on their restoration.

We take the view that we shouldn’t treat ecosystems like museums – they possess their own life force (mauri) which interacts with the world around them, and so we encourage communities to consider their history with the lake and their values relating to it and develop restoration goals on that basis.

Russleigh Parai, Kaupapa Māori scientist, Lakes380

Documenting the present while exploring the past

The Lakes380 science team is looking at lake health as it is now – using water samples and surface sediment samples to measure water quality and biodiversity (organisms living in the lake).

The team is also investigating lake health as it used to be – using sediment cores. These are tubes of mud that are carefully extracted from the lake so that the layers that have built up year after year remain intact. Everything that happens in or around a lake leaves a trace in the sediment.

Lake sediments are natural archives that continuously record environmental history, providing measures of current and historical aquatic ecosystems and water quality. The Lakes380 team use these sediment cores to explore historical shifts in lake health and this is equivalent to centuries of environmental monitoring. Because we are capturing 1000 years of lake history with each core, we are gaining incredible amounts of new knowledge about how and why our lakes have changed over time.

Dr Marcus Vandergoes, Lakes380 programme co-leader

It may seem unusual that looking back in time helps scientists learn how to protect or restore lakes into the future. Techniques like eDNA, high-resolution scanning and carbon dating provide clues to what lake catchments looked like before humans arrived in Aotearoa and how things have changed over time. For example, the image below shows changes to Horseshoe Lake in Hawke’s Bay. Pollen from the sediment core shows that, prior to human settlement, the lake was surrounded by lush native forests. Some of the forest was cleared by Māori, with a steady decline after European settlement. Horseshoe Lake is a wildlife reserve that is being restored. Evidence from the core indicates restoration plantings should include podocarps like mataī, rimu and kahikatea.

Building research methods and national datasets

The Lakes380 science team is developing new methods to assess lake health from surface sediments. These new methods are being used to investigate changes due to natural and human disturbances to forecast how lakes might respond to climate change and to understand what causes a lake to change from a healthy condition to an unhealthy one.

The team is also creating samples and datasets of lake cores, water and sediment samples they’ve collected from the lakes and metadata (other information like catchment land use and lake depth) for the lakes they’re studying. The samples and datasets will become public resources for both Aotearoa and the global scientific community.