Functional traits help identify remote sensing blind spots in polar vegetation mapping

Accurate estimates of vegetation cover underpin ecological monitoring and conservation, yet lichens, the dominant primary producers across the coldest biomes remain poorly represented. Recent satellite-derived products provide Antarctic-wide estimates of vegetation cover, but detecting lichens remains challenging due to unique spectral characteristics, making it unclear where and how much lichen cover is missed. Interpreting and validating these products requires understanding of how lichens and their detectability vary across Antarctic landscapes. Here, we examine whether lichen growth form associates with topographic features to support accurate estimation of lichen cover and evaluation of remote sensing performance. Through intensive lichen surveys on East Lagoon Island (western Antarctic Peninsula), we quantified growth-form cover in 381 quadrats and fitted a spatial model with topographic predictors to estimate cover across the island. Crustose lichens were most abundant on flatter terrain, fruticose lichens dominated sloping surfaces at intermediate topographic wetness, and foliose lichens peaked at intermediate slope. The model showed consistent predictive performance (jackknife R 2 = 0.38) and estimated that lichens cover 42.6% of the island's surface, partitioned into 16.2% crustose, 19.5% fruticose, and 6.9% foliose lichens. These values dwarf the 0.23% cover indicated by satellite-derived vegetation products. High-cover areas were dominated by fruticose lichens on sloping terrain, yet were absent from satellite-detected areas, indicating systematic underdetection linked to habitat and functional composition. Our results demonstrate that lichen cover is substantially underestimated in current vegetation products. By identifying overlooked lichen communities, our study provides a benchmark for diagnosing remote sensing blind spots and validating vegetation indicators in lichen-dominated environments.