In Antarctica, the McMudro Dry Valleys polar desert ecosystem is defined by exposed soils, glaciers, stream channels, and permanently ice-covered closed-basin lakes. There is no vegetation cover across the landscape, and lake levels are maintained by the inflow of glacial melt and water/ice losses to the atmosphere. This landscape experienced a summer air temperature decrease from 1987 to 2001. In response to this cooling, the ecosystem responded with decreased populations of soil invertebrates, increased lake ice thickness and decreased primary productivity in the lakes, and decreased algal mat coverage in streams. In the 2002-03 austral summer, a period of warm air temperatures and very few clouds produced the greatest glacial melt on record (since 1968). Since this ‘flood year’, summer climate has steadied with no trend in mean air temperature or annual solar radiation. The flood year disturbance added water to soils, decreased lake primary productivity, and scoured stream algal mats. However, in more than a decade since the flood year, stream algal mats have increased significantly, as has lake primary productivity, though soil invertebrate populations have had no temporal trend.
This polar desert ecosystem has demonstrated its resilience as temporal trends of several ecosystem characteristics have either reversed or changed to have no temporal trend through time. The relatively stable summer climate that followed the flood year, for more than a decade, provided perhaps the best test of the resilience of this system. Two additional high flow seasons occurred in the late 2000s, though not as great as the 2002 flood year. The ecosystem does not show repeat disturbance response to these two later summers, suggesting that the system has improved its resiliency since the 2002 flood year.