The extreme conditions of the Antarctic continent represent a significant barrier to life. Vegetation of terrestrial Antarctica is restricted to regions free of ice, which make up only 0.3 percent of the continent. Antarctic plants live at the physiological limits of survival. Land plants are mostly confined to the cryptogams: mosses dominate the ice-free land and can form complex communities in areas that receive adequate summer meltwater. Intrinsically, Antarctic mosses represent unique diminutive communities at the limits of survival, ecologically they provide habitat for invertebrates, and globally they can be seen as sentinels for global environmental change. There is evidence for rapid environmental change already occurring on the Antarctic continent: the Peninsula is one of the fastest warming regions on the planet, East Antarctica is undergoing warming and drying, and the entire continent is subject to high UV-B levels as a result of ozone depletion. Already at the limits of survival, Antarctic mosses are likely to be particularly sensitive environmental change. Indirect effects of climate change such as water relations will probably have a greater impact than rising temperatures alone. Mosses may benefit from the short term reduction in stress that follows warmer temperatures. However the long term effect is more complex, particularly combined with competition from invasive species interactions. Community level shifts in moss distribution and diversity are likely, as well as possible local extinctions. Understanding the response of moss communities to environmental change requires a combination of long term field studies, incorporation of new technologies and continued monitoring programs, including conservation plans in a proactive response.