AVUELO Endmember Diversity, Its Relationship with the Dimensions of Biodiversity, and Implications for Current and Future Imaging Spectroscopy from Space

Quantifying plant diversity from space remains challenging due to the traditionally coarse spatial and spectral resolution of remotely sensed data relative to the inherent vegetation canopy variability. Traditional spectral diversity metrics assume homogeneous pixel composition and fail to account for sub-pixel heterogeneity, limiting their effectiveness in complex ecosystems, including the tropics. Spectral unmixing offers a promising solution by decomposing mixed pixels into pure spectral signatures (endmembers) and their corresponding abundances, enabling species-level identification and diversity assessment. Previous studies have demonstrated the potential of endmember diversity (EndDiv) as a proxy for plant diversity in grassland using simulated spaceborne imaging spectrometers applied to 1-m airborne data. However, the approach's effectiveness in dimensionally complex tropical forests remains unexplored. The Airborne Validation Unified Experiment: Land to Ocean (AVUELO) campaign provides an opportunity to address this knowledge gap through its comprehensive dataset of 1-m and 3-m airborne imaging spectroscopy data collected with AVIRIS-3 and across diverse tropical forest types. This study applies spectral unmixing to simulated spaceborne imaging spectrometers using multi-resolution airborne spectroscopy data from Barro Colorado Island (BCI). This airborne data is convolved to match existing and planned spaceborne imaging spectrometer systems to later calculate endmember diversity across BCI. We compare derived endmember diversity metrics with field-based biodiversity indices, including spectral, functional, taxonomic, and phylogenetic diversity, to evaluate the efficacy of spaceborne imaging spectroscopy missions by: (1) assessing the effectiveness of endmember diversity for quantifying plant diversity in tropical forests, (2) determining optimal spatial and spectral resolution requirements for biodiversity monitoring, (3) establish relationships between EndDiv and multiple dimensions of biodiversity in this Neotropical forest, and to finally (4) compare it with other remotely sensed biodiversity metrics. The results will inform the design and application of current and future spaceborne imaging spectroscopy missions for global biodiversity monitoring, particularly in tropical ecosystems where biodiversity assessment is challenging.