Unlocking the secrets of forests as carbon sinks: innovative tools to measure forests’ climate mitigation potential

By Sofie Van Winckel & Arne Van Wolputte

How can we maximise the carbon stocks and carbon sequestration potential of forests – by managing or not managing them? And how can carbon Monitoring, Reporting and Verification (MRV) be made effective and affordable as part of the proposed EU Carbon Removal Certification Framework (CRCF) regulation? KU Leuven’s MSc students Arne and Sofie are on a journey to answer these complex questions using different high-tech tools, including the Arboreal App, an iPad with LIDAR and a computer model based on satellite and field data. Read on and join them in uncovering the secrets of climate mitigation in INFORMA’s case studies!

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Picture this: as the first light of dawn gently spills over the horizon, you emerge from your tent to behold a breathtaking panorama – a lush valley stretching out beneath the canopy of a verdant forest. We are two Belgian students, Arne and Sofie, and this was one of the captivating scenes that greeted us during the fieldwork of our master’s thesis in the Catalan INFORMA demo site, near the majestic Pyrenees. Energized by a nourishing breakfast, we geared up, laced our hiking boots, and set off eagerly into the wilderness to uncover its mysteries.

Walking in the forest, everyone observes different things. Maybe you notice the different bird songs, the cool temperature in summer, or the beauty of spring flowers. However, even far beyond the experiential wonders, the forest offers us a multitude of services. Climate regulation is one of those services that is especially crucial in current times of climate warming. Excessive emissions of greenhouse gases, like carbon dioxide (CO2) by fossil fuel combustion, deforestation and forest degradation, are disturbing the natural cycle of carbon. Its heat-trapping properties cause an increase in the earth’s temperature at such a high speed that you can notice the differences even within the timespan of your own life. It is in this context that forests can come to the rescue, as so-called ‘nature-based solutions’. Trees and other plants take up atmospheric carbon in the form of CO2 through photosynthesis. In this way, they store the carbon in their biomass; this process is called ‘carbon sequestration’. Like that, forest ecosystems can absorb about 27% of the annual fossil fuel emissions worldwide, while they store already 45% of the terrestrial carbon.

The amount of carbon that is stored in a forest depends on complex relationships between species composition, the disturbance history of the site, the tree age, forest structure etc. Notice that we can influence all these parameters through forest management! This is especially the case for above-ground biomass, which includes stems, branches and leaves of trees. Through our research at KU Leuven, we want to answer the following research questions:

  1. How might the LiDAR scanner included in recent iPad devices be leveraged to assess above-ground biomass?
  2. What is the influence of forest management on the above-ground carbon stock in a forest?
  3. What is the influence of forest management on the above-ground carbon sequestration in a forest?

The first research question is the focus of Arne’s research, while Sofie tries to find an answer to questions 2 and 3.

Carbon markets as a climate mitigation tool

To answer the first research question, Arne has to study the economic context of his work. Carbon markets offer potential for mitigating climate change, but their reliability depends on effective measuring of carbon. Unfortunately, that’s the crux of the matter. Making Monitoring, Reporting and Verification (MRV) more affordable while maintaining sufficient reliability is therefore imperative.

In the quest for more effective climate action, the European Commission has proposed the Carbon Removal Certification Framework (CRCF) regulation. This framework aims to address the current lack of a robust certification scheme by laying down rules for MRV based on four key quality criteria: quantification, additionality, long-term storage, and sustainability (QU.A.L.ITY). While the CRCF sets out to improve transparency in carbon markets, challenges persist, particularly in establishing cost-effective monitoring methods. Although the framework isn’t expected until May 2025, the technical readiness for MRV is essential for stakeholders investing in climate solutions.

A novel app-based approach, called Arboreal Forest has potential to fulfill this call. The Swedish app can be installed on any mobile device with a built-in LiDAR, such as the iPhone 13 Pro and the iPad Pro. Armed with both traditional tools – a trusty tape measure and vertex – and the cutting-edge application, Arne ventured into Belgium’s Brabants Wouden National Park and the forests surrounding the Segre-Rialb basin, in the Spanish Pyrenees. The goal was clear: to determine the accuracy and cost efficiency of inventorying with the Arboreal Forest app, using conventional forest biomass assessment as a benchmark.

Carbon stocks vs. carbon sequestration

While Arne was focusing on the first Research question, Sofie investigated the second and third.  These may look similar, but there is an important difference stock and sequestration. In unmanaged forests, stands typically consist of older trees compared to a managed forest, where trees are harvested when they reach a certain age or size. Young trees grow faster, and in this growth process they sequester carbon faster than old trees. However, this sequestered carbon does not stay in the forest, but leaves the forest as wood products. In an unmanaged forest, the carbon remains stored in the trees until they degrade.

This logic reflects the scientific consensus that existed for a long time: carbon sequestration rates are higher in managed forests, carbon stocks are higher in unmanaged forests. During the last decades however, several studies countered this idea with several findings. Unmanaged forests would still continue to sequester carbon, because they keep growing even at an older age. Moreover, their young trees would grow at a speed surpassing the rate of decay observed in older ones. Forest management can also be seen as an opportunity to optimize carbon stock in a forest by choosing specific species and reducing competition among trees. Moreover, it can protect the forest for climate change related disturbances like wildfires thus avoiding potential massive releases of carbon. Until now, a lot of controversy exists about the subject; the INFORMA Forest Management Platform, a large European dataset of unmanaged forest patches, paired with nearby managed patches, to be launched soon on the INFORMA website, will offer opportunities to obtain clarity.

To manage or not to manage? That is the question

Sofie is comparing carbon stock and sequestration between managed and unmanaged patches from the INFORMA Forest Management Platform, more particularly in  the Brabantse Wouden NP (Belgium) and the Segre-Rialb Basin (Spain). She calculates the carbon stock from the tree stem diameter and the tree height, measured in the field, using so-called ‘allometric relationships’. Using these field data, she can calibrate a model using open access Sentinel-2 satellite images to estimate above-ground biomass in unmeasured forest areas. The above-ground biomass is then directly related to the above-ground carbon stock. By comparing the stock over a time period since 2015 (when the Sentinel-2 mission was launched), she will derive the sequestration rate. To manage or not to manage: that is the question that this study will help to solve in regard to climate mitigation.

Between August and October 2023, with the valuable aid and support of Centre de la Propietat Forestal (CPF) and our mentors at the KU Leuven, we conducted the field measurements, and final results of the research are expected in May 2024. These results will guide policy makers and forest managers in using the full potential of the forest as a nature-based solution to climate warming. By embracing innovative, technological approaches, we are paving the way for a more sustainable future. Imagine the impact of streamlined biomass assessment on conservation efforts, forest management, and climate change mitigation! Together, let’s explore the possibilities and strive for a world where technology works hand in hand with nature to safeguard our planet’s precious resources.