Is Antarctica Greening?

Abstract

Earth's polar regions are experiencing significant climate change, impacting global oceanographic and weather patterns. Arctic "greening" is well studied, but a debate has emerged about whether similar trends are occurring in Antarctica and whether and how remote sensing can assess them. Recent studies have introduced a concept of "greening" in Antarctica, framed primarily around moss cover expansion over bare ground. This interpretation differs from Arctic greening studies, which focus mainly on changes in vascular plant productivity and successional dynamics. This paper evaluates the Antarctic greening concept, focusing on how Normalized Difference Vegetation Index (NDVI)-based methods are applied and interpreted in this context, considering regional limitations in technology, data availability, and the unique Antarctic vegetation characteristics. Unlike the Arctic, Antarctic vegetation consists mainly of nonvascular organisms (algae, cyanobacteria, lichens, and bryophytes) that interact with slow-weathering soils with minimal organic inputs. These biological and environmental differences likely influence NDVI greening metrics and their ecological relevance, but remain poorly understood due to limited long-term data and validation. Despite advances in remote sensing, Antarctic vegetation mapping remains in its early stages. The small size and patchy distribution of vegetation complicate detection of presence and extent, and even with modern satellites, capturing subcentimeter annual growth rates remains challenging. The lack of historical high-resolution imagery hampers change detection, limiting our ability to track habitat expansion, vegetation dynamics, and community composition changes over time. Based on critical assessment, we identify serious concerns regarding the accuracy and interpretation of NDVI-based greening trends in Antarctica in recent studies, particularly in relation to technological constraints and biological realism. To address these issues, we propose a refined framework for interpreting NDVI data in Antarctica, aiming to prevent misleading conclusions about vegetation changes and trends. This framework suggests an urgent need for re-evaluation of how "greening" is both quantified and interpreted in Antarctica.

Keywords: NDVI; biological realism; climate change; field mapping; ground truthing; moss; remote sensing; vegetation trends.