Life in the cold
Before starting my PhD, I imagined Antarctica as a vast, barren icescape. I pictured scientists drilling into the ice to unveil the secrets of past climate and, of course, I pictured penguins. These aren’t uncommon images; after all, Antarctica is the coldest continent on Earth and well over 99% is permanently covered in ice. However, through the research and fieldwork opportunities I’ve been lucky enough to participate in, I discovered a much more fascinating environment than I ever expected. Now when I picture Antarctica, I see a testament to life’s resilience, thriving against all odds in a harsh, inhospitable environment.
Less than 1% of Antarctica currently contains habitable conditions suitable for supporting the growth of land- and snow-based photosynthetic life. These areas, consisting of seasonally ice-free terrain and coastal snowpacks, are home to some of the most resilient organisms on the planet, including mosses, lichens, algae and cyanobacteria. These particular vegetation types are both non-vascular and cryptogamic, meaning they lack specialized tissues for transporting water and nutrients, and most reproduce via spores. Apart from two native species of vascular plant and one non-native invasive species of grass that are also found on the northern Antarctic Peninsula and/or offshore islands, no other plant life has been physiologically capable of colonizing in Antarctica’s consistently frigid conditions. The resulting lack of biological competition results in a simple ecosystem, allowing cryptogams to dominate and thrive in the Antarctic landscape.
Moss carpet (Sanionia sp.) on Robert Island, South Shetland Islands, Antarctica. Image: Alex Thomson.
Growth of Antarctica’s cryptogamic vegetation primarily occurs during the short austral summer (December to February), when temperatures are slightly warmer and water availability from snow and ice melt is higher. However, in Antarctica, survival must be prioritized, and these non-vascular vegetation types adopt important desiccation and cold tolerance mechanisms to survive the extreme polar conditions. As a result, annual growth rates are slow and species diversity and abundance is relatively low across the continent.
Small but significant
Slow growth rates and the low abundance, biomass and diversity of vegetation in Antarctica simply reflect the harsh environmental conditions. Nevertheless, Antarctica’s vegetation plays a key role in ecosystem functioning. Understanding how life operates in hostile conditions can even provide insights into how it might persist on other planets. On a larger scale, lichens and mosses act as important bioindicators of regional climate change while the simplicity of the ecosystem forms a natural test bed for understanding the relationships between cryptogam coverage patterns and environmental changes across other parts of the globe. The wealth of research opportunities available from this small reserve of vegetation in Antarctica is disproportionately large, yet still remains largely underappreciated.
Pale green lichen (Usnea aurantiaco-atra) among mixed fellfield on Livingston Island, South Shetland Islands, Antarctica. Image: Felix Grewe.
This, compounded by the practical inaccessibility of much of the continent for traditional survey work, might partly explain why the total area and spatial coverage of vegetation at the continent scale has remained unknown until now. However, this has become a time-pressing issue, as recent and projected environmental changes in Antarctica are predicted to alter the structure and functioning of this vegetation in the future (see our paper). Additionally, the human-assisted introduction of non-native species to Antarctica poses a significant risk to its unique ecosystem. A continent-wide survey of vegetation underpins our ability to monitor large-scale distribution shifts in the long term and better protect vegetated areas which may be at heightened risk from the combination of environmental changes and increasing scientific activities and tourism.
Our footprint in Antarctica: colours of moss (Sanionia sp.) on Robert Island, Antarctica. Image: Alex Thomson.
Marking the baseline
Our international team, made up of researchers from the University of Edinburgh, Norwegian Institute for Nature Research, British Antarctic Survey and the Scottish Association for Marine Science, used multiple years of Sentinel-2 satellite imagery and field measurements to achieve the ambitious goal of mapping vegetation at a finer scale than previously possible across the whole Antarctic. Utilizing the different spectral properties of Antarctica’s major vegetation types was key for identifying their presence, and the use of satellite imagery was crucial for practically achieving non-destructive mapping over such a large area.
Recording the location of moss with a dGPS on Robert Island, Antarctica. Image: René Quinán/INACH.
With a continent-scale baseline of Antarctic vegetation finally in place, we can now address some critical questions that will enhance our understanding of this unique ecosystem, including:
How much vegetation is there in Antarctica, and what does this mean for terrestrial and cryospheric primary production at the continental scale?
Is vegetation present in previously unknown areas?
Are there any vegetated areas that are inadequately protected under the current Antarctic Specially Protected Area (ASPA) system?
We can already address some of these questions, as demonstrated in our paper (linked above), where we present spatial coverage and area estimates of green vegetation, lichens and green snow algae across Antarctica. In total, we detected 44.2 km² of vegetation, making up less than 0.12% of Antarctica’s total ice-free area. To put this into perspective, if you were to take the entire area of detected vegetation in Antarctica and place it in the UK, it would only cover an area three times the size of Lake Windermere in the Lake District. Alternatively, if we use a spatial comparison from the US, it would cover less than the size of Manhattan Island. This naturally low area of vegetation across Antarctica highlights the importance of generating a continent-scale map to identify the key oases of vegetation presence, thus enabling a well-informed and holistic approach to conservation.
Antarctic fur seal resting on a moss bed with orange crustose lichen on the rocks in the background, Robert Island, Antarctica. Image: René Quinán/INACH.
This mapping project was funded by an NERC and UK Space Agency PhD studentship and achieved through international collaboration, with fieldwork supported by the British Antarctic Survey, Antarctica New Zealand, Instituto Antarctic Chileno, and the US Antarctic Program. Check out our paper for more insights into how we mapped Antarctica’s frosty flora.
Landscape mosaic of mosses and cyanobacteria on Robert Island, Antarctica. Image: Andrew Gray.