Adam Hartland

Selected publications

Four recent papers that show the range of the work, from a Miocene climate archive to the chemistry of a working drinking-water supply. The full list is on Google Scholar and ORCID.

Carbonate-system perturbation by invasive bivalves threatens drinking-water security in calcium-limited catchments

Hartland A, Melchior M, Hamilton DP, Lehto NJ, Mullarney JC, Sandwell D, Robb L, Jabbari A, Lang J, Clague J, Özkundakci D, Hofstra D (2026) Environmental Science & Technology, 60th anniversary special issue. doi 10.1021/acs.est.6c03421

Since arriving in the Waikato River in 2023, gold clams (Corbicula fluminea) have removed about 14 tonnes of calcium carbonate a day, depleting dissolved calcium by a quarter and raising alkalinity. A twenty-year treatment plant record shows arsenic removal depends on that calcium. When it fell in late 2024, treated water breached the drinking-water standard at five plants. The same mass balance gives a basin-scale clam census that matches diver surveys.

Late Miocene Arctic warmth and terrestrial climate recorded by North Greenland speleothems

Moseley GE, Koltai G, Baker JL, Wang J, Stoll H, Donner A, Friedrich L, Spötl C, Smith MP, Scholz D, Cheng H, Hartland A, Hejny C, Edwards RL (2025) Nature Geoscience 18: 1252 to 1258.

Cave minerals from eastern North Greenland record repeated permafrost-free intervals between about 10 and 5 million years ago, with mean annual temperatures around 14 degrees higher than today at atmospheric carbon dioxide above roughly 310 parts per million. That is a moderate threshold, and it says something about how sensitive the Arctic is. Cover article, December 2025 issue.

Pronounced drought and wet periods during the Maya Terminal Classic period reconstructed using stalagmite calcium isotopes

James DH, Bradbury HJ, Carolin SA, Breitenbach SFM, Cheng H, Orland IJ, Curtis JH, Hartland A, Gallup C, Kwiecien O, Mason AJ, Henderson GM, Brenner M, Turchyn AV, Hodell DA (2026) Earth and Planetary Science Letters 691: 120226.

A 1,500-year stalagmite record from the Puuc region of Yucatán, Mexico. Calcium isotopes, which respond to how much water sits in the rock above the cave, give a semi-quantitative rainfall history: a wet interval around 865 to 890 CE, then a 43 percent reduction in mean rainfall lasting until 1160 CE, through the decline of the Classic Maya cities.

Warming drives dissolved organic carbon export from pristine alpine soils

Pearson AR, Fox BRS, Hellstrom JC, Vandergoes MJ, Breitenbach SFM, Drysdale RN, Höpker SN, Wood CT, Schiller M, Hartland A (2024) Nature Communications 15: 3522.

Fluorescent organic matter trapped in two South Island flowstones and a lake sediment core gives a 14,000-year record of carbon leaching from alpine soils. Export doubled to tripled during the early Holocene, when temperatures were 1.5 to 2.5 degrees warmer than pre-industrial, and fell as the climate cooled. Temperature, rather than vegetation cover, was the main control.

Other key papers

Hartland A, et al. Decoupled infiltration and isotope signals reveal a hidden East Asian monsoon megadrought. Nature Communications in revision

Höpker SN, Breitenbach SFM, Grainger M, Stirling CH, Hartland A (2024) Characterising the decay of organic metal complexes in speleothem-forming cave waters. Geochimica et Cosmochimica Acta 373: 98 to 108.

Giesche A, Hodell DA, Petrie CA, … Hartland A, … Breitenbach SFM (2023) Recurring summer and winter droughts from 4.2 to 3.97 ka in north India. Communications Earth & Environment 4: 138.

Lindeman I, Hansen M, Scholz D, Breitenbach SFM, Hartland A (2022) Effects of organic matter complexation on partitioning of transition metals into calcite: cave-analogue crystal growth experiments. Geochimica et Cosmochimica Acta 317: 118 to 137.

Mohammadi A, Corbett T, French A, Lehto NJ, Hadfield J, Jarman P, Sandwell D, Shokri A, Schipper L, Hartland A (2022) Application of diffusive gradients in thin films for monitoring groundwater quality. ACS ES&T Water 2: 518 to 526.

Nava-Fernandez C, Hartland A, Gázquez F, et al. (2020) Pacific climate reflected in Waipuna Cave drip water hydrochemistry. Hydrology and Earth System Sciences 24: 3361 to 3380.

Blyth AJ, Hartland A, Baker A (2016) Organic proxies in speleothems: new developments, advantages and limitations. Quaternary Science Reviews 149: 1 to 17.

Hartland A, Larsen JR, Andersen MS, Baalousha M, O'Carroll D (2015) Association of arsenic and phosphorus with iron nanoparticles between streams and aquifers: implications for arsenic mobility. Environmental Science & Technology 49: 14101 to 14109.

Research

My research sits within aquatic and carbonate geochemistry. Three questions run through it.

What do cave minerals record about past rainfall?

Speleothems (cave carbonate deposits) grow from dripwater and keep a chemical record of it. I develop proxies based on the decay of organic metal complexes that return past infiltration in volumetric units rather than as a relative index, and that have revealed megadroughts which conventional isotope records miss.

How is rising carbon dioxide changing fresh water?

As atmospheric carbon and temperatures rise, freshwater systems are trending more acidic and losing oxygen. Using the Waikato River as the test case, the Emerging Climatic Pressures programme is establishing the baseline chemistry that governs what this means for water quality and water security.

What do nanoparticles do at the boundary between dissolved and particulate?

Organic and mineral nanoparticles, soils, pyrolysed organic matter and mineral surfaces carry trace elements, compete for them, and set the rate at which they are exchanged. This is the common thread from arsenic in alluvial aquifers to the signal transferred between a cave drip and the crystal it forms.

Polished section of stalagmite GT1, Guillotine Cave, South Island, New Zealand — Stalagmite GT1, Guillotine Cave, South Island.

As Principal Investigator on the MBIE Endeavour Fund programme Emerging Climatic Pressures, run with Lincoln Agritech Ltd, I lead work on the effects of climate change in freshwater ecosystems. The programme looks at how the cycling of carbon between land, water and atmosphere changes the acidity and biogeochemistry of water. What this means for future water quality and water security is being investigated by an interdisciplinary team using real-time sensing, experimentation, numerical modelling, and kaupapa Māori (indigenous sociological) research.

My scientific roots trace to subterranean caves and aquifers. I began by using geochemical methods to understand the structure and function of sub-surface food webs (stygofauna), then progressed to reading the geological record of climate change encoded in speleothems with greater fidelity. Alongside the New Zealand caves, I have worked on raised coral atolls in the South Pacific, where the rainfall is governed by El Niño Southern Oscillation and the islands sit in the cyclone belt. Tropical island karst continues to be a focus of my work, with records in development spanning the Holocene, through the last glacial period and beyond.

More recently I have taken a leading collaborative role in characterising the impact of massive carbonate biomineralisation by invasive gold clams on the Waikato River, a critical waterway in Aotearoa New Zealand. This is an Emerging Climatic Pressures collaboration with Earth Sciences New Zealand.

Other examples of the same approach include the modification of nutrient availability to phytoplankton as carbon dioxide changes (MBIE, Emerging Climatic Pressures), the retention of nitrate by pyrolysed organic matter (biochar) in edge-of-field denitrifying bioreactors (MBIE), and the transfer of a signal between a cave drip and the crystal it forms (Rutherford Discovery, Marsden).

Jeff Lang conducting a photogrammetric survey inside Te Reinga Cave — Jeff Lang (postdoc) surveying Te Reinga Cave for a 3D model that gives structural, hydrologic and speleogenic insight.

Adam Hartland — Explaining the group's research to KuDos (watch on YouTube).

Sampling a stalagmite underground — Sampling a stalagmite. Flowstone cores from the South Island underpin the *Nature Communications* soil carbon record.

Active programmes

Gold clams (Corbicula fluminea) dominating the river bed at Lake Karapiro, densities exceeding 1,000 per square metre

MBIE Endeavour Fund, $11.4M, 2023 to 2028

Emerging Climatic Pressures on the Waikato River

Establishing the baseline chemistry that governs how rising carbon dioxide affects fresh water, using the Waikato River as a test case. Geothermal carbon dioxide accounts for about 71% of the river's carbon budget, and invasive gold clams strip roughly 14 tonnes of calcium carbonate a day while mobilising arsenic. The models the programme is building are intended to transfer to other freshwater systems. Partners: Uppsala University, Helmholtz UFZ, Universities of Waikato, Otago, Auckland, Victoria and Lincoln, iwi, Waikato River Authority, Waikato Regional Council and Hamilton City Council, water utilities (IAWAI Flowing Waters, WaterCare Ltd).

In revision, Nature Communications

Decoupled infiltration and isotope signals reveal a hidden East Asian monsoon megadrought

First use of the kinetic proxy in a high-resolution Chinese speleothem, showing a major infiltration collapse at 5.2 ka that δ¹⁸O and prior calcite precipitation proxies do not record. Uncertainty is propagated across nine sources, giving past infiltration in volumetric units.

In preparation, Earth-Science Reviews

Nanoscale biogeochemical intermediaries

A review of nanoparticles and organic matter as intermediaries at the boundary between dissolved and particulate phases, where they carry trace elements, compete for them, and set the rate at which they are exchanged.

Cave drip splash on a stalagmite, photographed by Garry K. Smith

Open-source tool

Dr Paleo / PaleoDripRates

A web application that reconstructs speleothem drip rates from trace element chemistry, using Bayesian inversion through partition coefficients. It includes a depth-only mode and propagates uncertainty through the calculation. github.com/waikatosci/paleodriprates

Image © Garry K. Smith

Career

My interest in what happens below the surface began with an undergraduate project on groundwater food webs under the Canterbury Plains. Since then the work has taken me through cave and karst systems on four continents, alluvial aquifers in Australia, and the rivers and lakes of Aotearoa New Zealand. After a decade as an academic at the University of Waikato, I joined Lincoln Agritech Ltd, an R&D company owned by Lincoln University, where I lead the Emerging Climatic Pressures programme.

2022 to now

Senior Scientist, Lincoln Agritech Ltd

Science Leader, Emerging Climatic Pressures programme (LVLX2302). Adjunct Associate Professor at the University of Waikato and Lincoln University. Founder and Managing Director, Waikato Scientific Ltd.

2016 to 2022

Rutherford Discovery Fellow, University of Waikato

Five-year research fellowship (Royal Society Te Apārangi, $800K). Promoted to Associate Professor in 2020. Founded the Waikato Environmental Geochemistry group.

2012 to 2022

Lecturer, Senior Lecturer, then Associate Professor, University of Waikato

Ten years establishing and running a research group. EU MSCA RISE PI (QUEST programme, linking Cambridge, JGU Mainz and PIK Potsdam). Marsden Fund panel member (Earth Sciences and Astronomy, 2022 to 2024).

2011 to 2012

Postdoctoral Fellow, University of New South Wales

National Centre for Groundwater Research and Training. Iron nanoparticle and arsenic interactions during surface water and groundwater exchange.

2011

PhD Geochemistry, University of Birmingham

NERC Doctoral Scholarship. Colloidal geochemistry of speleothem-forming groundwaters. Supervisor: Prof. Ian Fairchild.

2007

BSc (Hons, First Class) Environmental Science, University of Birmingham

Most Distinguished Student award.

Instruments

SYP Mark III autosampler: the sampling needle above the vial carousel — The SYP Mark III sampling head and vial carousel. sypsampler.com

The SYP began as a problem in a cave. Sampling dripwater through a season means either living underground or leaving something behind that can do it for you. The early prototypes went into Waipuna Cave and then to Niue, where they had to contend with a hostile environment and tenacious coconut crabs!

Waikato Scientific exists to provide equipment other people can rely on when they can't stay behind: automatic sensing and sampling technology for remote environmental deployments. The company builds, sells and supports the SYP Mark III Automatic Water Sampler, which collects up to 58 discrete, sealed samples over year-long deployments on a rechargeable battery. It is used by researchers at Cambridge, UC Davis, Vanderbilt, Cornell College, Rouen and Northumbria, among others, and was named in Science Advances in 2025 for its part in a Maya drought reconstruction. Open-source research software is at github.com/waikatosci.

Waikato Scientific founders Sebastian Hoepker and Adam Hartland testing an early SYP production unit in Waipuna Cave — Waikato Scientific founders Sebastian Höpker and Adam Hartland testing an early SYP production unit in Waipuna Cave.

Writing and media

Public writing, broadcast and press on caves, climate and the Waikato River. Longer pieces appear on River Diaries, my Substack.

River Diaries (Substack), August 2026

The gold clam and the end of an era in freshwater management

Nutrient management remains necessary, but it is no longer sufficient. On why climate, rising ecosystem respiration and an invasive ecosystem engineer now compound with the familiar drivers of Waikato River health, and what that means for Plan Change 1 and the national freshwater conversation.

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Water New Zealand webinar, July 2026

Invasive clams and the Waikato: emerging risks for source water and treatment

Findings from the Emerging Climatic Pressures programme, alongside operational perspectives from Lutra and Watercare on source water monitoring, treatment process design and risk planning.

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The Conversation, April 2026

Toxic blooms and invasive clams are forcing a rethink on the Waikato River

On the environmental pressures reshaping New Zealand's longest river: geothermal carbon dioxide, invasive gold clams, and the difficulty of responding to several of them at once.

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The Conversation, December 2025

Gold clam invasion in NZ threatens drinking water for millions of people

How Corbicula fluminea strips around 14 tonnes of calcium carbonate from the Waikato River each day, disrupting water treatment chemistry and mobilising arsenic into forms that conventional treatment may not remove.

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Waatea News, December 2025

Golden clam invasion: a growing threat to New Zealand's water security

Interview on the biosecurity implications of Corbicula fluminea for freshwater infrastructure, hydroelectric operations and indigenous species.

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RNZ, Our Changing World

Caves reveal past climate change

On using cave mineral archives to reconstruct New Zealand's climate history, and what stalagmite chemistry says about past rainfall variability.

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NZ Herald, 2020

Climate change: what ancient caves reveal about NZ's future deluges

On the use of speleothem records to understand how New Zealand's rainfall extremes may intensify under climate change.

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RNZ Checkpoint, 2019

Waitomo Caves shut down for high carbon dioxide levels

Interview on elevated carbon dioxide in the Waitomo Glowworm Cave and what it means for cave conservation.

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EU Horizon Magazine, 2019

Cave rock studies provide window into ancient civilisations

Feature on the EU-funded QUEST programme and the development of new speleothem proxies linking cave chemistry to past climate.

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EGU Imaggeo, 2019

Our QUEST for innovative tools to understand changing environments and climates

Photo essay on the QUEST research network's fieldwork across New Zealand cave systems.

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Royal Society Te Apārangi, 2017

Beyond palaeoclimate: new horizons for cave science

Commissioned for the Society's 150th anniversary feature. On what caves can record beyond climate: earthquakes, volcanic eruptions, soil carbon loss, and the New Zealand lineage of cave science running back to Chris Hendy.

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1 News, 2017

Search for clues about how climate change will affect NZ heads deep underground

Television coverage of the cave monitoring programme and what stalagmite chemistry can say about New Zealand's rainfall future.

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Stuff, 2017

Waikato University scientist's cave study aims to measure climate change

On the Rutherford Discovery Fellowship programme to develop quantitative speleothem proxies of past rainfall in New Zealand.

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Track record

$14.5M in competitive research funding as Principal Investigator

Leading an $11.4M MBIE Endeavour programme on the Waikato River

Nature Geoscience, Nature Communications, EPSL and ES&T since 2024

Founder of Waikato Scientific, with samplers deployed on six continents

Ten years leading a research group at the University of Waikato