|Paper title||The 1st ESA CCI Biomass Change Workshop – Outcomes of a global virtual event|
|Form of presentation||Poster|
The primary science objective of ESA’s Climate Change Initiative Biomass project is the provision of global maps of above-ground biomass for four epochs (mid 1990s, 2010, 2017 and 2018) and, based on these, being capable of supporting the quantification of above-ground biomass change. Biomass in this context is given as above-ground forest biomass (AGB), which is defined following the FAO as the dry weight of live organic matter above the soil, including stem, stump, branches, bark, seeds and foliage woody matter per unit area, expressed in t/ha. AGB is also an Essential Climate Variable (ECV) within the Global Climate Observing System (GCOS).
Part of the project was holding a Biomass Change mapping workshop in late 2020. Due to the COVID-19 pandemic, the workshop was organized as virtual event 19th October – 6th November 2020. This virtual technical workshop enabled scientists from around the globe engaged in biomass change mapping to jointly formulate the underlying principles of forest biomass change estimation and the challenges connected with this and to develop meaningful estimates of the accuracy of such change measures.
Special circumstances - the pandemic - require special measures, in this case the virtual format of the workshop considering different time zones. The virtual workshop was running over a period of three weeks, where active participation was restricted to short periods within that timeframe. A domain was acquired and a dedicated website was created. A limited number of online presentations was made available at the first day of the workshop. They had to be watched prior to the live online-discussions concerning different topics (3 x 10 minutes per topic). Throughout the workshop further discussion were also possible via a dedicated discussion forum. To make participation possible for attendees from different parts of the world, all discussion rounds were hosted live in specific time slots. In this way, every interested participant of the workshop was given the opportunity to attend at least at one discussion round per week.
The first week was addressing issues related to “Defining and quantifying biomass change”. Three subtopics were selected: 1) The nature of change, 2) Change on the ground (e.g. linking traditional inventories with EO, standardisation of change descriptions and metrics, permanent plots with repeat coverage, biome-based allometric models), 3) Assessing the accuracy of AGB change estimates. The second week of the virtual workshop was handling questions related to “Biomass change from space” with the three subtopics 4) Change algorithms and methodologies, 5) Space and time considerations and 6) Validation of change.
During the workshop, a number of key questions concerning biomass change in general have been formulated jointly together:
How can global AGB be best mapped according to the controls on AGB change and to assess maximum biomass potential (consideration of climate, topography, latitude, flora and fauna)? And is this the best way to consider the different controls on biomass amounts (with respect to soils, air temperature, water resources, species distributions)?
Should biomass change be understood as relative to previously recorded amounts or maximum site potential amounts? This leads to the next question: Under which constraints is the detection of biomass change less relevant (e.g. in old growth forests or temporary biomass reduction by thinning) and how can we define threshold for saying that biomass change occurred?
How do we best describe the time-scales of biomass change ranging from rapid losses within a few days to weeks (deforestation, thinning) to yearly or decadal changes connected with forest growth?
This was leading to the overarching question: What is the best framework to use and follow for global biomass change classification?
All these issues are important for the continuation of the ESA CCI Biomass initiative. But the outcomes may also serve as a guideline for future fields of research and method development, which can be of use for the upcoming ESA P-band Biomass mission, now planned for launch in 2023.