Human trampling reduces soil faunal populations and soil respiration in the McMurdo Dry Valleys, Antarctica

Antarctica is the most pristine continent on Earth. However, since the initial explorations of the 19th Century the number of people visiting Antarctica has increased and the rate of visitations has accelerated over recent decades. We assessed the impact of human foot-traffic on soils in the McMurdo Dry Valleys, the largest area of ice-free land on the continent and a region with increasing scientific and recreational visitation. There are no vascular plants in this ecosystem, and soil nematodes are the most abundant and widespread animals. We measured the abundance of nematodes, rotifers, and tardigrades in the top 10 cm soil, as well as soil CO2 fluxes, in areas that received high, medium and low levels of trampling in Taylor Valley. The abundance of both nematodes species (Scottnema lindsayae and Eudorylaimus sp.) decreased by 60% and 75%, respectively, in heavily trampled areas and the impact was even more severe in the top 2.5 cm soil. Trampling also increased the relative abundance of dead Eudorylaimus sp. individuals. Soil CO2 fluxes were 60% lower in heavily trampled areas at the most productive site; however, CO2 fluxes were not affected in the two other basins, possibly because the flux in these sites was near minimum detection limits. Our results show that human foot-traffic significantly disturbs soil faunal communities and soil respiration in the Dry Valleys. Since human activity in this region is likely to increase over coming decades, management practices that limit impacts, such as confining human traffic to established footpaths, may be necessary to minimize disturbances to this ecosystem.