- Could you briefly describe RIFT?
Jérôme Demarty: RIFT has two main research axes. The first axis is more methodological and technical in nature: we are seeking to improve systems for measuring greenhouse gas fluxes in tropical and Mediterranean regions. Some of our focal systems—flux towers—are already established and operational. However, our work also involves setting up new ones. The second axis is more scientific in nature: we want to exploit and generate value from the data produced.
RIFT has brought together around sixty academic collaborators. This relatively large number is a result of the project’s broad scope and dispersed field sites, which demand significant efforts by researchers and technicians in the Global North and South. Access to field sites is more difficult in the Global South, which means that logistics are more complicated. A small portion of our project is therefore dedicated to training technical staff at the 13 study sites in the Global South, which are located in West Africa (n = 7), the Mediterranean (n = 3), Asia (n = 1), and South America (n = 2).
Most of our collaborators in the Global North come from CIRAD and IRD, although some are affiliated with INSU and various universities. RIFT is a five-year project that got started in May 2023, with its scientific launch taking place in early December 2023.
- What is RIFT’s role on the international stage?
Jérôme Demarty: RIFT’s work is key to current international projects focused on transitions (Paris Agreement, Net Zero by 2050), which rely on the data collected by monitoring gas exchanges with the atmosphere. These measurements make it possible to track fine-scale temporal trends and accurately estimate carbon balances. At present, the international research community is unable to monitor certain terrestrial ecosystems because flux towers are labour and cost intensive. Each tower must meet a justifiable need, and they require regular maintenance to function properly. At the same time, as I mentioned earlier, these data are essential. In particular, they provide the basis for the development and validation of global models, whose purpose is to monitor and predict climate change patterns and related changes in natural resources. Current global models lack the data needed to be applied worldwide, which is why we must acquire more extensive data through field experiments. RIFT has a major part to play because it will facilitate model validation and refinement.
- RIFT is focused on flux towers. Can you explain what they are?
Jérôme Demarty: Flux towers host many sensors and instruments dedicated to measuring hydrometeorological variables and gas exchanges between the Earth’s surface and the atmosphere. These towers are self-contained and could be established anywhere in theory. They continuously record data using a dedicated system powered by batteries recharged by solar panels. Data are gathered 24 hours a day at high frequencies: meteorological data are collected every minute, and there are 10–20 measurements per second for the gas exchanges. It is evident why logistics are an important part of running flux towers, as regular visits must be made for maintenance and data transfer.
- Could other methods or tools be used instead?
Jérôme Demarty: Right now, there are no other technical approaches we could use to measure fluxes in the field. That said, we do have indirect methods for estimating surface fluxes, which utilise spatial data or land surface models. They have certain advantages. At the same time, flux towers remain the standard for collecting local-level data and are thus an indispensable tool for developing the indirect methods.
- Can flow towers help with the lack of data for poorly studied areas, particularly those in the Mediterranean?
Jérôme Demarty: Flux towers can only be established in areas with the right field conditions. Because someone must visit these towers on a regular basis, the lack of technicians in the Global South is an issue. Generally speaking, it is easier to build a flux tower in the Global North, as it can be placed near a laboratory performing related research. Because towers are expensive (€50,000 each), it is not feasible to set them up in large numbers in hard-to-reach areas. The present paucity of data for the Global South largely stems from a lack of funding. Consequently, the aim of our project is to transmit familiarity and information about these techniques and to establish reference sites in African countries or in tropical regions, where flux towers are less common.
For models to be as finely tuned as possible, we must have measurements from a variety of ecosystems. Savannahs and tropical forests are playing a major role in climate change, which means we must establish flux towers in these ecosystems to expand the global database. Therefore, RIFT’s objective is to put together a data collection network focused on these ecosystems.
- What types of measurement devices can be found on flux towers? What sort of data are they collecting?
Jérôme Demarty: Flux towers have two broad categories of devices:
First, there are instruments for measuring gas exchanges between the Earth’s surface and the atmosphere: energy fluxes, such as the amounts of energy absorbed and released by the vegetation, as well as the associated amount of carbon fixation.
Second, there are instruments for gathering data on temperature, humidity, and wind speed, all meteorological factors that affect plant functioning, soil humidity, soil temperature, and many other above- and below-ground processes.
A single flux tower can host more than 40 sensors and measurement devices.
- What challenges are the scientific community facing when it comes to exploiting these tools and the resulting data?
Jérôme Demarty: Apart from the funding constraints, an issue that looms large is the fact that flux-tower data are representative of small surface areas. For example, measurements from a forest versus a field will reveal very different dynamics, even if the sites are located next to each other. However, you cannot build an indefinite number of towers. The challenge is thus to identify relatively homogeneous areas and environments that are representative of broader scales, which allows you to obtain standardised, representative measurements.
For instance, flux towers in forests must rise above the tree canopy, so the support structure is a constraint. In contrast, in fields, a simple support structure suffices.
Additionally, the tower’s devices must be regularly cleaned. We can use the Sahel as an example: there is dust everywhere, and devices must be kept clean to collect accurate measurements. For all flux towers, it is necessary to drop by every 2–3 weeks to switch out the memory cards that store the data, check on the batteries, and ensure that the devices are still functioning. This all adds up to a lot of maintenance work.
To establish flux towers in hard-to-access ecosystems for which data are scarce, we are collaborating with CIRAD and IRD. They have long-standing relationships with countries in the Global South. We are also partnering with university researchers and engineers who have immigrated abroad to help organise the necessary maintenance visits. That said, one of RIFT’s main objectives is to train local technicians and PhD students so that they can maintain this infrastructure over the long term.
Jérôme Demarty: Our project is unique for two reasons.
First, the data we produce will have great international value. The flux-tower research community is already international because of the need to build very large databases. However, these databases need far more data from ecosystems in the Global South.
Second, we are establishing protocols based on pre-existing standards to help certify data quality.
- What are the main expected results of your work?
Jérôme Demarty: In addition to everything I have already mentioned, RIFT wants to solidify ties between the research communities studying water versus carbon. We have strong relationships with researchers who are developing models of carbon functions, fluxes, and stocks. Consequently, RIFT frequently interacts with other FairCarboN target projects, resulting in integrated, complementary efforts. What's more, our data could serve as the basis for new international research projects. We are convinced that more collaborative projects are in our future because the data we produce will be of interest to the whole community at one point or another.
