The Longest Baseline Record of Vegetation Dynamics in Antarctica Reveals Acute Sensitivity to Water Availability

Abstract

Antarctica plays a central role in regulating global climatic and oceanographic patterns and is an integral part of global climate change discussions (Rogers et al., 2020). Warming and mass loss of outlet glaciers as described in the Sixth Assessment Report of the IPCC have been mainly observed in West Antarctica, whereas warming trends in East Antarctica have been seen as localized and inconsistent (Turner et al., 2009). Parts of East Antarctica are projected to experience greater-than-global warming in the 21st century (Meredith et al., 2019), especially in coastal areas due to relatively stronger Southern Ocean warming and effects of ozone recovery (Bracegirdle Abstract Against a changing climate, the development of evidence-based and progressive conservation policies depends on robust and quantitative baseline studies to resolve habitat natural variability and rate of change. Despite Antarctica's significant role in global climate regulation, climate trend estimates for continental Antarctica are ambiguous due to sparse long-term in situ records. Here, we present the longest, spatially explicit survey of Antarctic vegetation by harmonizing historic vegetation mapping with modern remote sensing techniques. In 1961, E. D. Rudolph established a permanent survey plot at Cape Hallett, one of the most botanically diverse areas along the Ross Sea coastline, harboring all known types of non-vascular Antarctic vegetation. Following a survey in 2004 using ground-based photography, we conducted the third survey of Rudolph's Plot in 2018 using near-ground remote sensing and methodologies closely mirroring the two historic surveys to identify long-term changes and trends. Our results revealed that the vegetation at Cape Hallett remained stable over the past six decades with no evidence of transformation related to a changing climate. Instead, the local vegetation shows strong seasonal phenology, distribution patterns that are driven by water availability, and steady perennial growth of moss. Given that East Antarctica is at the tipping point of drastic change in the near future, with biological change having been reported at certain locations, this record represents a unique and potentially the last opportunity to establish a meaningful biological sentinel that will allow us to track subtle yet impactful environmental change in terrestrial Antarctica in the 21st century. Plain Language SummaryIn early 2022, record-breaking high temperatures were recorded all over Antarctica, sparking concerns about the icy continent's future. Although the effects of climate change have been observed in West Antarctica, much less observation is available for East Antarctica, where almost 90% of the Antarctic ice mass is located. It is now, that East Antarctica is at a tipping point for change, and it is now, that we need to establish progressive conservation measures. What is at stake? The vegetation in East Antarctica is distinct. Any organism that managed to survive here has highly specialized traits, and we only find lichens, mosses, cy...

High Resilience and Fast Acclimation Processes Allow the Antarctic Moss Bryum argenteum to Increase Its Carbon Gain in Warmer Growing Conditions

“…With high plasticity indicated by the rapid physiological and morphological changes in B. argenteum , the suggestion that the extreme seasonality of Antarctica leads to high resilience is supported. Additionally, B. argenteum populations in Cape Hallett studied over time have remained stable [ 54 ], which further corroborates their inherent resilience to change. Although general warming trends have not yet been exhibited across continental Antarctica [ 85 ], the region is predicted to become increasingly exposed to thermal stress in the form of heatwaves [ 86 , 87 ].…”

“…With the versatility in carbon gain seen under our pulse warming treatment, mosses in continental Antarctica are likely to increase growth rates and potentially expand in coverage or density under predicted short- or long-term warming. However, enhanced growth and expansion are dependent on how increased temperatures alter water availability and permafrost active layer depth, factors which can greatly affect moss performance [ 54 , 90 ].…”

“…Maximum air temperatures are above 0 °C almost every day from mid-December to the end of January [ 51 ]. The mean summer temperature of the period from 1965 to 2018 was −4.83 ± 1.68 °C, with a minimum temperature of −27.22 °C and a maximum temperature of 5.97 °C [ 54 ]. Snowfall totals about 1755 mm (actual snow depth) and falls on 160 days each year (averages for the years 1957 to 1963; [ 55 ]).…”

Antarctica's vegetation in a changing climate

“…This is because survey periods have to span decades rather than years or seasons to allow for significant and accurate detection of growth and the establishment of robust baselines (Convey et al, 2018;Green et al, 2011;Turner et al, 2018). It is because of these complications, that so far, only three "long-term" baseline studies exist in and around Antarctica: two of them situated in the maritime Antarctic [Signy Island (Cannone et al, 2016(Cannone et al, , 2022, and Argentine Islands (Fowbert & Smith, 1994;Parnikoza et al, 2009)], and one in continental Antarctica (Brabyn et al, 2006;Colesie et al, 2022).…”

“…The lack of baseline knowledge on moss growth and its natural variability is still limiting our ability to evaluate change. The only study, to date, to report the long-term baseline ecology of Antarctic mosses is reporting strong seasonal phenology, distribution patterns that are driven by water availability, and steady perennial growth of moss at Cape Hallett in continental Antarctica (Colesie et al, 2022). Amesbury et al (2017) have shown that with the Antarctic Peninsula becoming warmer and wetter, moss growth rates have quadrupled.…”