An Interview with Dennis Baldocchi and Vona Medeler (FBF 2021)

July 24, 2023

Intertidal coastal ecosystems are an essential part of our ecosystems. Not only are they present all over the world, but they are increasingly recognized to be as productive as tropical forests within the global carbon budget. Despite their relevance, the contribution of intertidal coastal ecosystems remains unknown and more than ever under threat from global changes. Moreover, these ecosystems are currently under threat from global changes and human activities. 

That is why Professor Dennis Baldocchi from the Department of Environmental Science, Policy & Management at UC Berkeley, and Professor Vona Meleder from the Départment des Sciences de la Vie of the University of Nantes, wanted to take a closer look at those ecosystems, and more specifically at the contribution of theses ecosystems to the global carbon cycle. This research would be the first time ever that such predictions would be made and will make humanity understand the consequences of the dysfunction of such ecosystems. We sat down with them to learn more about the motivations behind their project, what their research consists of, how it is groundbreaking within the research of the global carbon cycle, and what opportunities the France-Berkeley Fund gave them. 

Vona MéléderDennis Baldocchi

Can you both introduce yourselves and talk about your academic journeys that led you to this project? 

DB: I was reared on an almond and walnut ranch along the Sacramento-San Joaquin delta.  As a Northern Californian native, I am inspired by the landscapes of our region and how they are shaped by the local weather and microclimates.  Foundational experiences include attending 4H camp in the redwoods and oak woodlands near Angwin, camping with my family up and down the Sierra Nevadas and visiting relatives on ranches in Marin and Sonoma counties.

I received my BS from UC Davis in Atmospheric Science and my MS and PhD from University of Nebraska in bio-environmental engineering. After graduate school, I worked as a micrometeorologist at the NOAA Atmospheric Turbulence and Diffusion Division in Oak Ridge, TN. I have been at Cal since 1999. I am also a second-generation Cal employee, as my mom was the secretary for Brutus Hamilton, the track coach in the early 1950s. Today, I am a professor of biometeorology. I am interested in measuring and modeling trace gas exchange between managed and natural ecosystems and the atmosphere.  

VM: I was born in Brittany, in the North-West of France, but I grew up in French Guyana (South America). Maybe it is for these reasons I am so close to nature, and more specifically to the coastal environments. I am a traveler at heart, and I love to discover new cultures and countries with my family. I am excited when my work is directly connected to environmental challenges, and I would like to contribute as much as possible to the mitigation strategies we have to develop to cope with climate change.

I received my MS from Paris VI University, and my PhD from Nantes University in 2003. After a postdoc at the French Institute for the exploitation of the sea, in Brest (Brittany), I was hired as an associate professor in 2007. Today, I am Professor of Marine Biology, and my main interest is to estimate the contribution of mudflats inhabited by microalgae biofilms in the Carbon budget. For that, I couple remote sensing images from different platforms (satellite, plane, drone …) with CO2 fluxes. 

What made you interested in intertidal coastal ecosystems and the carbon uptake of these ecosystems ? 

DM: Our delta was a vast area of intertidal, vegetated wetlands that developed since the last ice age.   After the Gold Rush, these lands were drained for agriculture.  The exposure of these rich organic peat soils to oxygen are causing them to be decomposed by microbes. Over the last 120 years this land has dropped 10 meters below sea level.  This process is not sustainable if we are to protect the water delivery system for the state of California.  The state is restoring non-tidal and tidal wetlands across the Delta, and we are studying the efficacy of these projects by measuring their greenhouse gas fluxes; we are measuring the carbon dioxide, water vapor and methane exchange of these restoration projects with the eddy covariance method.  This is an exciting opportunity as these ecosystems have the potential to be among the strongest carbon sinks in the world and can be effective natural climate solutions. 

We live along the SF Bay estuary and there are strong gradients in salinity and growth, so we are curious about how these restoration projects may vary along this gradient.   Scientifically, we share many similarities to the Loire River Delta that Prof. Meleder is studying near Nantes, France.   She is an expert in assessing productivity of mud flats in France and does so adroitly using remote sensing and hyperspectral reflectance.  She was able to bring a new set of eyes to my research.  And she was interested in learning about the eddy covariance method, which we use to measure trace gas fluxes.  Together, our goal is to perform a handshake between gas fluxes measured over mudflats and wetlands with eddy covariance and remote sensing indices and use this information to upscale fluxes in time and space where we are not making direct greenhouse gas flux measurements.

VM: I would like to add that wetlands, and moreover mudflats are the “poor relatives” of the Blue Carbon concept. Research is often focused on mangrove and coral reefs, and people have a positive perception of these coastal ecosystems. For wetlands, is it not the same! So, therefore, it is not easy to restore and protect ecosystems that people don’t mind. I am often sad to realize that people are not reached by the aesthetics of these seascapes. So, one of my objectives is to demonstrate to people that these ecosystems are highly useful: they protect people against sea rise level, are biodiversity hotspots, and are strong carbon sinks. And they could be so beautiful and have a smoothing effect.

How and why did you decide to work together on your research? 

DM:  Prof. Meleder reached out to me. I did not know her, but I was interested in a possible collaboration as she had skills and overlapping interests that I thought would forge an ideal collaboration. And it is my experience that visitors enrich the experiences of my students and postdocs.  

She wanted to come to the Biomet Lab, as we are experts in using the eddy covariance method to measure carbon dioxide fluxes over landscapes.  And she wanted to live in Berkeley with her family during her sabbatical to give them new experiences of living in California.

VM: In 2019, preparing my first proposal for a project about remote sensing and CO2 fluxes, I read all of Dennis’ papers. I was so impressed by his approach, that I want to be trained by him. So, as we say in France “qui ne tente rien n’a rien”. I sent him a message to know if he would agree to host me for several months, and he answered yes! I was so happy, and glad!

Can you explain a bit more in detail what your research focuses on?

DM:  The Berkeley Biomet Lab has established a network of long-term sites measuring greenhouse gas fluxes over tidal and non tidal wetlands in the delta.  We use the eddy covariance method to make direct flux measurements and we use high resolution remote sensing to upscale these fluxes in time and space.

Prof. Meleder was interested in expanding her set of measurements of hyperspectral reflectance over different mudflats in the world, especially mudflats where eddy covariance measurements of carbon dioxide were being collected.   To meet her goals, she needed to get new data from the Bay Area.  The sites in the Delta that I operate are vegetated and little mud is exposed.  So, they are not ideal for Prof. Meleder’s prime goal.  However, my former postdoc, Patty Oikawa, is operating a study site on the SF Bay near the San Mateo Bridge, Eden Landing, that is an ideal tidal mudland site for data collection.   The mudflats are replete with photosynthesizing diatoms that Prof. Meleder studies.  They are able to fix carbon by ‘eating sunlight’.  They are an important component of the food web in estuaries and her work is novel for quantifying the rates by which they fix carbon.

What are the next steps within your research? 

DM and VM: We want to extend the time series of our flux measurements across tidal and non-tidal sites and to use next generation remote sensing to upscale our flux measurements across our SF Bay estuary and the Loire estuary outside Nantes, where Dr. Meleder lives. And Prof. Meleder intends to operate an eddy covariance flux system over her estuary near Nantes to measure greenhouse gas fluxes.

What are the reasons that pushed you to apply for the FBF (France-Berkeley Fund)? 

DB:  Having a French American spouse, having spent sabbaticals in Bordeaux and Montpellier, and being a fan of French food and wine, I am guilty of being a Francophile.  Prof. Meleder provided a great opportunity when she approached me about a possible visit and collaboration.  The Berkeley-France fund seemed a perfect way to make this a reality.  By coming to California, her children were able to attend Berkeley schools and improve their English and she got a chance to experience all the hamburgers in town.  We were hoping to reciprocate and visit Prof. Meleder in France, but Covid restricted our ability to travel.  

What has the FBF done for your research?  What type of opportunities did it open for you? 

DB: This collaboration gave time and inspiration for Prof. Meleder to write a proposal to form a global network of colleagues looking at the photosynthesis of mudflats. My lab has been among the developers of a global network of global carbon flux measurements, Fluxnet and provided a template for Prof. Meleder.  

Having Prof. Meleder in town provided an opportunity for outreach to the French community. My spouse is a member of the Berkeley Faculty Section French club and they invited Prof. Meleder to give a presentation on her research and life in France.  It was among the best presentations that the group has received in years.

Our original reciprocal visit was postponed due to Covid. We hope to visit Prof. Meleder in Nantes in the future, visit her field sites and learn about her research at her home institute.

We want to thank both Dennis Baldocchi and Professor Vona Meleder for taking the time to answer our questions. We wish them all of the luck for the rest of their study and collaboration together.