Recent Warming and Cooling in the Antarctic Peninsula Region has Rapid and Large Effects on Lichen Vegetation

Abstract

The Antarctic Peninsula has had a globally large increase in mean annual temperature from the 1951 to 1998 followed by a decline that still continues. The challenge is now to unveil whether these recent, complex and somewhat unexpected climatic changes are biologically relevant. We were able to do this by determining the growth of six lichen species on recently deglaciated surfaces over the last 24 years. Between 1991 and 2002, when mean summer temperature (MST) rose by 0.42 °C, five of the six species responded with increased growth. MST declined by 0.58 °C between 2002 and 2015 with most species showing a fall in growth rate and two of which showed a collapse with the loss of large individuals due to a combination of increased snow fall and longer snow cover duration. Increased precipitation can, counter-intuitively, have major negative effects when it falls as snow at cooler temperatures. The recent Antarctic cooling is having easily detectable and deleterious impacts on slow growing and highly stress-tolerant crustose lichens, which are comparable in extent and dynamics, and reverses the gains observed over the previous decades of exceptional warming.

Figure 1

Study site. Location of the moraine under study in Livingston Island, South Shetland Islands, Antarctica (a) and photos in January (b) of the moraine (left panels) and detail of the lichens (right panel) growing on a boulder in January 2002 (upper panel) and 2015 (lower panel). The map was created using ArcGIS 10.4 ESRI (https://www.arcgis.com).

Figure 2

Relationship between annual growth rate and mean summer temperature. (a,b) Growth rates (mm y⁻¹) calculated for the crustose lichens Acarospora macrocyclos (), Bellemerea sp. (), Buellia latemarginata (), Caloplaca sublobulata (), Rhizocarpon geographicum, () and the fruticose lichen Usnea antarctica () from measurements in 1991 (from new surface to 1991, 34 years), 2002 (1991 to 2002, 11 years), and 2015 (2002 to 2015, 13 years) and mean summer (January, February and December) temperatures for the same periods in Bellingshausen Antarctic Base, King George Island () (a) and annual growth rates for the same species related to mean summer temperature in Bellingshausen for the same periods (b).

Figure 3

Snow and ice accumulation trends in the last years in the surrounding of the Spanish Antarctic Base on Livingston Island. (a,b) Average thickness of the snow layer (, r² = 0.278) and number of days with snow (, r² = 0.471) in the last 7 years (a) and surface mass balance series of Hurd Glacier (b). The grey bars represent the mass balances (positive values, winter balance and negative values, summer balances) and the red/blue bars to their right the resulting annual balances: red if negative (net mass loss), blue if positive (net mass gain). The dashed lines represent the 14-year averages for winter and summer balances. Years shown are southern hemisphere hydrological years.