Feature, News from the Field

Research at Brooklyn Wildlife Sanctuary sheds light on termites’ methane emissions

10 Oct. 2023
Wayne Lawler/AWC

Across Earth’s ecosystems, the carbon cycle circulates carbon in solid or gaseous forms between rocks, soils, vegetation, the ocean, and the atmosphere. Human activity, land use change, globalization, and carbon pollution of the atmosphere have greatly altered the natural carbon cycle, making it important to quantify its underlying processes and understand how they respond to global change.

In Australia, savannahs are a widespread bioregion covering 25% of the continent and are an understudied element of terrestrial carbon cycling. One unique feature of the Australian savannah is a high abundance of mound-building termites, which play an integral role in savannah carbon cycling by carrying out decomposition. Termites cycle carbon by breaking down dead plants; what was once living plant material that stored and sequestered carbon is released as termites carry out decomposition.

When termites break down plants, the released carbon can go into termite bodies, become incorporated into soils, or be emitted to the atmosphere as carbon-based gas. One of the most interesting ways termites interact with the savannah carbon cycle is by releasing methane.

Lots of busy C. acinaciformis soldiers initiating repairs after the mound wall was broken to take a sample. Termite soldiers defend the colony where it is exposed to the outside world, and the termite workers begin the patching process within minutes of the breach. Abbey Yatsko
Lots of busy C. acinaciformis soldiers initiating repairs after the mound wall was broken to take a sample. Termite soldiers defend the colony where it is exposed to the outside world, and the termite workers begin the patching process within minutes of the breach.

Methane is an important carbon-based greenhouse gas that traps much more heat in the atmosphere than carbon dioxide. For this reason, the scientific community is trying hard to closely understand and estimate all the different sources of methane, both natural and human.

The microbes within termite guts are responsible for generating methane, and in this way, termites serve as tiny cows by releasing methane as burps and farts!

Abbey Yatsko is a PhD candidate, from the Department of Biology, at the University of Miami, and is currently undertaking her research at Brooklyn Wildlife Sanctuary.

“In my Ph.D. I aim to determine how much methane mound-building termites in the Australian savannah release to the atmosphere.

“To do this, I measure termite mound methane release from three different savannah termite species (Nasutitermes magnus, Coptotermes acinaciformis, Amitermes laurensis) using an Infrared Greenhouse Gas Analyser (IRGA) as well as photogrammetry. I measure the mounds at different times of the year to see how methane release changes with various environmental conditions, such as more rainfall in the wet season or hotter temperatures in the late dry season. I am also testing how mound methane release changes throughout the day.”

The gas flux measurement setup. On the left, a PVC chamber is sealed to the mound surface using potting clay. The tubing connects the measurement chamber to the IRGA, which determines how much methane is leaving the surface of the termite mound, known as flux. Methane flux readouts are given in real-time on the computer, and the temperature of the chamber is manually recorded using a thermocouple. Abbey Yatsko
The gas flux measurement setup. On the left, a PVC chamber is sealed to the mound surface using potting clay. The tubing connects the measurement chamber to the IRGA, which determines how much methane is leaving the surface of the termite mound, known as flux. Methane flux readouts are given in real-time on the computer, and the temperature of the chamber is manually recorded using a thermocouple.

“So far, I have found that N. magnus mounds release more methane than other species. Hotter temperatures increase mound methane flux, and methane release changes throughout the day. The dataset is not yet complete as I have one more field campaign in the mid-wet season before I can build a full model of annual termite methane flux for these three savannah-dominant termite species.”

To determine how many termite mounds are out in the savannah, Abbey is flying a multispectral drone and will test if machine learning algorithms can pick out termite mounds from the imagery.

“Ultimately, I will derive landscape-level estimates of termite mound methane flux by pairing mound-level flux measurements with remotely sensed mound density, contributing to our understanding of savannah methane budgets and carbon cycling.”

Climbing atop an N. magnus mound to take a termite sample for identification. These mounds are the largest in the study. Supplied by Abbey Yatsko
Climbing atop an N. magnus mound to take a termite sample for identification. These mounds are the largest in the study.

“Conducting this research project at AWC’s Brooklyn Wildlife Sanctuary has been fun, but full of challenges: from getting bogged during sampling campaigns to camping out by the termite mounds for around-the-clock measurements, I have learned so much from the termites and how they interact with the entirety of the savannah ecosystem.

“I am continually grateful for the time and energy that project collaborators, station managers, field assistants, and funding agencies have put into supporting my Ph.D. research. And of course, the termites themselves never fail to inspire me whenever I am in the field – their little bodies are carrying out immense, mysterious processes that continue to shape and define the savannah landscape no matter what.”

A time-lapse of the mound measurement process. First, the IRGA is set up and turned on, and then PVC chambers are mounted to the outside of the mound. Flux measurements are made at 4-5 locations on the mound, and then the mound is broken into to search for termites for identification. Video by Caleb Jones.

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