About

I am an Associate Professor of Behavioral Science and Economics and Faculty Research & Cumulative Initiatives Faculty Fellow at The University of Chicago Booth School of Business. I am an economist applying insights from psychology to important economic problems, particularly in development economics. I hope that by combining tools and theory from both economics and psychology my work can improve our understanding of difficult problems in economics, identify new problems that the classical approach may miss, and highlight directions for further psychological research.

Research topics

• Environmental science
• Environmental chemistry
• Physical geography
• Ecology
• Chemistry
• Geology
• Soil science
• Oceanography
• Geography
• Geomorphology
• Biology
• Meteorology
• Earth science
• Paleontology

Selected publications

• Climate sensitive methane release from sediment-laden channels in Arctic rivers 

  2026-03-14

  articleOpen accessCorresponding

  Arctic rivers can act as a route for methane (CH4) to enter the atmosphere from landscapes impacted by ongoing permafrost thaw and climate warming. Thermokarst erosion and thaw induced mass-wasting are underway across the Arctic, increasing organic matter supply to river systems that could act as substrates for methanogenesis. In addition, warming of air and water temperatures could increase methanogenesis in analogy with responses seen in other aquatic, non-fluvial settings. Despite this recognition, the source, drivers and sensitivity of Arctic river CH4 emissions to geomorphic and climate change remain obscured.Here, we apply novel sampling methods and use radiocarbon and a multi-stable isotope approach to quantify CH4 emissions, age and source in Arctic rivers of the Mackenzie River Basin across two field campaigns in winter 2023 and summer 2024. Despite evidence for CH4 oxidation, we find that sediment-laden Arctic Rivers are hotspots of CH4 release, both downstream of sites of increased thaw-driven mass wasting and within large channels of the river delta. We find that river CH4 emissions increase by three times in the summer season compared to the winter, sustained by an aged, but higher quality organic matter substrate. A detailed reach-scale CH4 budget reveals a high apparent temperature sensitivity of river CH4 emissions that has not been recognized before, suggesting that ongoing warming, permafrost thaw and increased erosion will increase river CH4 emissions in the Arctic.

  PublisherDOI

• Complex hydroclimatic drivers of peatland stream CO2 and CH4 emissions revealed from a multi-catchment temporal study

  2026-03-14

  articleOpen accessCorresponding

  Peatlands represent a dominant global soil carbon pool, but their role here is vulnerable to climate change and land use pressures. Peatland streams are known conduits of terrestrial carbon loss, rapidly transferring CO2 and CH4 from peat soils to the atmosphere. Despite their recognised contribution to global river greenhouse gas emissions, the hydroclimatic drivers here remain obscured across spatiotemporal gradients.To address these research needs, we applied a novel isotopic framework (radiocarbon, δ13C, δD, δ18O), to constrain age and sources of peatland stream CO2 and CH4, alongside constraints on hydrological flow paths and CH4 oxidation mechanisms. Over four seasonal visits, we sampled eight catchments on the Isle of Lewis, Scotland, spanning gradients of catchment areas, geomorphology, and land use. The Lewis Peatlands represent one of Europe’s largest continuous blanket bogs, and our catchments capture 30% of their surface area. All sites were subject to the same climate and underlying geology, enabling us to isolate spatiotemporal drivers across catchments.Chamber-based emissions (flux) measurements reveal high variability of both CO2 (–4.17 ± 2.35 to 106.73 ± 11.26 mmol m-2 d-1) and CH4 (0 to 2.44 ± 0.34 mmol m-2 d-1), with inconsistent coupling in the magnitude of CO2 and CH4 emissions, suggesting independent supply controls. We explore these catchment-specific patterns considering their geomorphological attributes. We find that both CO2 and CH4 fluxes decrease exponentially with catchment area. Surface moisture indices derived using remote sensing show stronger CH4 emissions in wetter catchments, while the magnitude of CO2 emissions was more strongly linked to temperature. Preliminary radiocarbon data hint that CO2 tends to become younger in drier catchments associated with summer sampling, validating the observed seasonal controls of CO2 dynamics. While stronger CO2 and CH4 fluxes generally aligned with younger carbon turnover, these pathways also act as a significant export mechanism for older carbon, with some of the highest fluxes formed of older carbon.Preliminary stable isotope data indicate greater inter-catchment variability in stream CH4 sources than CO2. Pending isotopic data will enable us to track these patterns over one year of sampling. Globally, only six published datasets report coupled river 14C-CO2 and 14C-CH4, making this one of the first studies to track these paired data over time. Combined with geochemical context and geospatial analyses, this framework will enable us to better constrain what are clearly highly dynamic and variable processes and avoid missing hotspots and key drivers of these peatland carbon loss mechanisms.

  PublisherDOI

• Higher, but more variable, annual CO2 emissions from lakes in drier Arctic landscapes

  Communications Earth & Environment · 2026-02-07

  articleOpen access

  Abstract Land-to-water hydrological connections represent a key regulatory mechanism of carbon transport, controlling carbon dioxide (CO 2 ) emissions from lakes; however, as of yet, there is no assessment of its role at a pan-Arctic scale across large climatic and topographical gradients. We hypothesized that hydrologically well-connected lakes in wetter regions are CO 2 sources fueled by stronger lateral fluxes of external carbon relative to drier regions. However, based on data from &gt;200 Arctic lakes, we found that lakes in drier regions have higher and more variable annual CO 2 emissions ( $${37.0}_{6.2}^{146.0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>37.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>6.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>146.0</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> gC m -2 yr -1 , $${{median}}_{Q1}^{Q3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mi>m</mml:mi> <mml:mi>e</mml:mi> <mml:mi>d</mml:mi> <mml:mi>i</mml:mi> <mml:mi>a</mml:mi> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Q</mml:mi> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>Q</mml:mi> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ) compared to lakes in wetter regions ( $${8.0}_{1.7}^{17.3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>8.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>1.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>17.3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> gC m -2 yr -1 ), with both the lowest and the highest fluxes recorded among dryland lakes. We hypothesize that with increasing wetness, the relative proportion of fluvial emissions increases, whereas in drier landscapes where lakes often have limited stream export, carbon inputs can be retained and more efficiently emitted from lakes.

  PublisherDOI

• Incorporating Soil Organic Carbon Dynamics into Global Hydrogen Uptake Models: A Focus on Microbial Activity

  2026-03-23 · 1 citations

  articleOpen access

  Abstract. Molecular hydrogen is a secondary greenhouse gas that indirectly contributes to climate forcing by extending the atmospheric lifetime of methane through competition for hydroxyl radicals. Soil serves as a major sink for atmospheric hydrogen, making accurate estimation of soil hydrogen uptake essential for understanding its role in atmospheric chemistry. Most existing process-based models of hydrogen uptake focus primarily on abiotic controls, such as soil temperature and moisture, while either neglecting or oversimplifying the role of biotic factors, particularly microbial activity. In this study, we refine four widely used hydrogen uptake models by integrating microbial activity rate modifiers and machine learning derived soil porosity. The microbial activity rate modifiers are derived from the decomposability of soil organic carbon, which is assumed to be a proxy for potential microbial activity. This leverages simulations of soil organic matter turnover provided by well-established and tested models of soil organic matter decomposition. This simple approach enables application of hydrogen uptake models from field to global scales. We have integrated our simulations of microbial activity into four widely used hydrogen uptake models. Model performance is evaluated against empirical datasets from four detailed studies of soil hydrogen uptake. Results show that replacing traditional texture-based porosity with machine learning derived estimates significantly improved physical transport modelling, particularly for the Bertagni and Ehhalt frameworks. Furthermore, incorporating the coupled climate-carbon microbial activity rate modifier consistently strengthened model performance, producing larger reductions in prediction error and more pronounced increases in correlation than using microbial activity alone, thereby providing a more realistic representation of soil microbial processes. These findings highlight the importance of including biologically relevant factors in atmospheric hydrogen modelling and offer a more mechanistic framework for predicting soil–atmosphere hydrogen exchange under diverse environmental conditions.

  PublisherOA PDFDOI

• Soil carbon residence time regulates the age of dissolved organic matter in global rivers

  National Science Review · 2026-04-21

  articleOpen access

  ABSTRACT Riverine dissolved organic carbon (DOC) constitutes a pivotal component in the Earth’s carbon cycle, yet little is known about the global patterns, sources, and factors governing lotic DOC. Here, we integrate a global dataset and employ machine learning to generate a global atlas of riverine DOC concentration and its radiocarbon (Δ14C) and stable-carbon (δ13C) isotopic signatures. Globally, riverine DOC has an average Δ14C value of –22.5‰ ± 144.0‰ (radiocarbon age of 221 years), with fossil carbon contributing a minor fraction (6.7% ± 3.0%). Terrestrial and autochthonous riverine production are the dominant DOC sources (&amp;gt;80%) at the global scale, with contemporary terrestrial DOC predominant in tropical rivers and within-river production prominent in those within temperate and semi-arid regions. Rivers draining high-latitude regions and high-elevation sites have the lowest Δ14C values (–353‰ to –78‰; ages between 3400 and 600 years). River Δ14C-DOC values correlate with soil organic carbon Δ14C values, but river DOC has much higher Δ14C values than subsurface soils indicating that riverine DOC originates from surface rather than subsurface soils. Because warming mobilizes aged organic carbon from permafrost soils, export to and processing of old carbon in recipient aquatic systems may accelerate with climate change.

  PublisherOA PDFDOI

• Lines in the landscape

  Communications Earth & Environment · 2025-08-22 · 6 citations

  articleOpen access

  Abstract Ditches (linear constructions which store and/or move water where humans prefer it to go), via irrigation, drainage, and power, have helped drive the development of human societies. Now, ditches and other linear channels, typically carrying water, are numerous and found on every continent. Their form varies widely with use, which includes land drainage, irrigation, transportation, and boundary marking. Ditches support and shape biogeochemical cycles, biotic communities, and human societies, at multiple spatiotemporal scales. However, ditches are frequently overlooked by researchers in many disciplines. Here, we review the largely unrecognized role that ditches play in environmental processes and human societies. The effects of ditches can be both positive (e.g., biodiversity refuges, water for food production, nutrient retention) and negative (e.g., greenhouse gas emissions, dispersal of pollutants). We call for future management to consider and enhance the multifunctional role that ditches can deliver at the landscape-scale.

  PublisherOA PDFDOI

• ABCFlux v2: Arctic–boreal CO ₂ and CH ₄ monthly flux observations and ancillary information across terrestrial and freshwater ecosystems

  2025-10-20

  preprintOpen access

  Abstract. Measurements of surface-atmosphere carbon dioxide (CO2) and methane (CH4) fluxes have been relatively sparse across the Arctic tundra and boreal biomes, causing significant uncertainties in carbon budget estimates from the region. While the availability of Arctic-boreal carbon flux data has increased substantially over the past decade, the data have remained spread across different repositories, scientific articles, and unpublished sources, making it difficult to leverage. Here we present a new dataset of monthly Arctic-boreal carbon fluxes (ABCFlux v2) across terrestrial (wetlands and uplands) and freshwater (lakes and rivers) ecosystems compiled from previous syntheses including the Arctic-boreal CO2 flux database (ABCFlux v1), the Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH4), and the Global River Methane Database (GRiMeDB). In addition, we consider data from general-purpose (e.g., Zenodo) and flux network repositories, literature, and site principal investigators. The dataset includes surface-atmosphere CO2 fluxes of gross primary production (GPP), ecosystem respiration (Reco), and net ecosystem exchange (NEE), alongside CH4 fluxes. For aquatic ecosystems, we split CH4 fluxes into diffusive and ebullitive flux pathways, and included potential emissions from transient storage in the water column (“storage fluxes”), alongside CO2 and CH4 concentrations dissolved in the surface water. Fluxes are measured through a variety of methods including chamber and eddy covariance techniques alongside bubble traps, ice-surveys, and concentration-based turbulence-driven modelling in aquatic ecosystems. The monthly flux data are reported together with supporting methodological and environmental metadata. The resulting ABCFlux v2 has 23,656 flux site-months, 8,182 concentration site-months, and 199 seasonal observations from 1,024 sites, and includes 55,560 reported fluxes (i.e. sum of GPP, Reco, NEE, and CH4 fluxes) from the years 1984 to 2024. The majority of monthly observations occurred after 1999. Wetlands had the highest number of site-month observations (8,641), followed by boreal forest (6,981), lotic ecosystems (6,275), lentic ecosystems (3,725) and upland tundra (3,308). Measurements of CO2 dominated the dataset across most ecosystem types (25,101) except for lentic ecosystems, where CH4 flux site-months (3,024) were more frequent than CO2 flux site-months (2,858). Overall, ABCFlux v2 includes 158 % more site-months for terrestrial CO2 flux data compared to ABCFlux v1. Integrating and updating BAWLD-CH4 flux data from growing season averages to monthly fluxes resulted in 5,671 site-months of chamber CH4 data compared to 762 site-years. This collaborative initiative, involving contributions from over 260 researchers, provides a comprehensive overview of the current state of the Arctic-boreal carbon flux network and its data, and serves as an important step in reducing uncertainties in Arctic-boreal carbon budgets and in enhancing our understanding of climate feedbacks. The data can be accessed at ORNL DAAC at https://doi.org/10.3334/ORNLDAAC/2448 (Virkkala et al., 2025b).

  PublisherOA PDFDOI

• 4C and GHG dynamics in bog pools of a rewetted peatland

  2025-03-14

  preprintOpen accessCorresponding

  Rewetted peatlands can have higher methane (CH4) emissions compared to undrained peatlands. However, the majority of studies have focussed on terrestrial emissions and have overlooked waterbodies such as pools and remnant ditches, and consequently, emissions from peatland waterbodies remain largely unknown. This study is primarily focusing on greenhouse gas (GHG) emissions from peatland waterbodies from two contrasting UK bogs: A lowland raised bog in north-west England (Risley Moss) and an upland blanket bog in north Wales (Migneint). Seasonal sampling of dissolved and ebullitive greenhouse gases (GHGs) is ongoing. In October 2024, sampling for radiocarbon (14C) analysis of aquatic CH4 and carbon dioxide (CO2) was completed at the Migneint site. Both diffusive and ebullitive pathways were sampled at 3 locations (a newer restoration pool, an older restoration pool and a natural pool). We will use the results of these analyses to answer the following questions:1) Does the 14C age of CH4 and CO2 vary between ebullitive and diffusive fluxes? 2) Does the 14C age of CH4 and CO2 vary between natural and restored pools, and with time since restoration?To date there is very limited data for the difference of ages between ebullitive and diffusive fluxes of different GHGs with no research previously asking this question. The use of ¹⁴C will help to determine the pathways of C between the different pool types and determine if the age of pathways varies between timescales of restoration and natural pools. ¹⁴C will also help determine if in fact older rewetted sites have become more stable in relation to age of C emissions and show if the pathways have shifted towards more modern C. Preliminary data for these questions will be presented during this session. It is hoped that the answers to these questions will help fill data gaps from these poorly understood waterbodies and improve our understanding of the GHG impacts of peatland restoration strategies. In future work we will expand the radiocarbon analysis to Risley Moss and other peatlands.

  PublisherDOI

• Impacts of warming and permafrost thaw on chemical weathering and riverine carbon fluxes on the Qinghai-Tibet Plateau

  2025-03-14

  preprintOpen accessCorresponding

  Climate warming and associated permafrost thaw can have multi-faceted impacts on carbon fluxes from inorganic and organic sources. Permafrost thaw unlocks large stores of organic carbon that can be mineralized and emitted as carbon dioxide (CO2) from rivers to the atmosphere, or transported downstream. Concurrently, permafrost thaw exposes minerals to weathering reactions that can both sequester or emit carbon. Finally, climate warming can affect reaction kinetics and the cycling of reactive fluids through the subsurface. To date, the tradeoff between these competing effects and their net effect on landscape-scale carbon fluxes remain unclear.Here, we present fluxes of dissolved solutes, riverine CO2 emissions, and carbon-isotope data from rivers that drain over 700,000 km2 of the Qinghai-Tibet Plateau, and that span a gradient in permafrost cover and temperature. Our data provide evidence for an interplay of organic-carbon degradation and inorganic chemical weathering that appear to modulate the balance of carbon sinks and sources. We find that net CO2 drawdown-fluxes from rock-weathering across the region account for ~35% of river CO2 emissions. Importantly, chemical weathering and organic carbon fluxes vary across the sampled permafrost gradient. In catchments underlain by continuous permafrost, CO2 drawdown from chemical weathering accounts for only ~25% of riverine CO2 outgassing. Conversely, carbon drawdown from weathering substantially outpaces riverine emissions in catchments with discontinuous or isolated permafrost.Based on these results, carbon fluxes from chemical weathering may become increasingly important with ongoing permafrost thaw, potentially even outpacing riverine CO2 emissions. In landscapes where carbonate and silicate weathering dominate &amp;#8211; such as over a large part of the QTP &amp;#8211; a substantial portion of additional CO2 production from permafrost thaw could, therefore, be buffered by weathering on human timescales.

  PublisherDOI

• Greenhouse gas release from warming mountain rivers in the Arctic

  2025-01-01

  article
  PublisherDOI

Frequent coauthors

• John A. Webb

  La Trobe University

  58 shared

• Edoardo Daly

  40 shared

• A. J. Dolman

  Vrije Universiteit Amsterdam

  34 shared

• Matteo Camporese

  University of Padua

  31 shared

• Ove H. Meisel

  Vrije Universiteit Amsterdam

  26 shared

• Jorien E. Vonk

  Vrije Universiteit Amsterdam

  23 shared

• P. Evan Dresel

  Agriculture Victoria

  21 shared

• Mark H. Garnett

  20 shared

Education

• PhD

  La Trobe University

  2015

Awards & honors

• Distinguished Alumni Award