Forest Biomass Reference System from Tree-by-Tree Inventory Data

In the context of the climate crisis, reducing our emissions must go hand in hand with strong carbon offsetting. One strategy for achieving this is to study the carbon and the biomass in forests. Today, there is no shortage of very impressive maps based on biomass products derived from Earth observation. But these maps strongly need to be validated by high-quality field data.

Some efforts have been put together by the CEOS community since 2018, by creating a global Forest Biomass System as an equitable and sustainably-funded system of recurrent site-based measurements that will serve as a lasting interface between the Earth Observation (EO) agencies and ground-based tree-by-tree measurement initiatives. This infrastructure is designed to become a common good for the entire EO community. From this context, the GEO-TREES initiative will be the world's first ground-based, open-access, equitably developed, forest biomass reference system designed to make global satellite-based forest carbon assessments actionable.

Through this structure, the GEO-TREES initiative is a win-win because: - sites partners benefit from funding and increased visibility; - existing networks benefit from continuity in funding streams; - the Earth observation community benefits from free access to biomass data, on a continuous and long-term basis.

Establishing a globally consistent system for measurement, reporting, and verification (MRV) of forest carbon stocks and fluxes is not simple, because forests are complex. But confronting this complexity is exactly what is needed, both to constrain models predicting the capacity of forests to store carbon as the planet warms, and to de-risk investment in forest carbon dioxide removal (CDR) – through restoration, regeneration and avoidance of forest loss. Communities, decision-makers, and forest carbon markets at all scales require reliable, cost-effective, real-time systems for MRV, and humanity needs a much stronger understanding of the impact of continued climate change on the capacity of forests to absorb CO2 in a warmer world.

The GEO-TREES initiative is built on four pillars:

1. A ground observation system: GEO-TREES is built upon preexisting field stations globally. The aim is to have the most accurate measurement of above-ground biomass and to measure and re-measure it at least every five years. Forest inventory plots, airborne and terrestrial laser scanning are used to provide high-quality geolocated aboveground biomass (AGB) at 0.25 ha scale in open access.
2. A Global vision: it has been shown that a coverage of 50-100 sites over the world would be a good structural, geographical and environmental representativeness (Labriere et al., 2023). Thus, the Forest Biomass Reference System will be centered on about 100 BRM sites distributed around the world, with strong priority placed on the tropics, and an additional 210 distributed BRM sites which do not require the long-term infrastructure of BRM sites but provide much better strategic gap-filling than is otherwise possible.
3. A long-term commitment: GEO-TREES provides a temporal link between all Earth observation missions by continuously supplying ABG. Thanks to these long-term measures, the initiative guarantees the commitment and participation of partners while representing only a few percent of the overall cost of all Earth observation missions.
4. A strong partnership and engagements: GEO-TREES relies on unprecedented multi-network collaborations, such as ForestGEO, TmFO and ForestPlots. These networks are managed by hundreds of dedicated specialists. In addition, GEO-TREES currently involves over 200 partners around the world, representing up to 50 years of collaboration, and provides strong support by committing to maintain strong representation and equitable funding of these partners.

These four pillars are implemented by a governance system built as follow: a coordination office is composed by an Executive Board and by a Scientific Advisory Committee. Both represents forest observation networks over the world. The coordination office work with the Biomass Reference Measurement Networks and with the Users such as the CEOS community or private sectors.