Effects of Human Trampling on Populations of Soil Fauna in the McMurdo Dry Valleys, Antarctica

Abstract

Antarctic ecosystems are often considered nearly pristine because levels of anthropogenic disturbance are extremely low there. Nevertheless, over recent decades there has been a rapid increase in the number of people, researchers and tourists, visiting Antarctica. We evaluated, over 10 years, the direct impact of foot traffic on the abundance of soil animals and soil properties in Taylor Valley within the McMurdo Dry Valleys region of Antarctica. We compared soils from minimally disturbed areas with soils from nearby paths that received intermediate and high levels of human foot traffic (i.e., up to approximately 80 passes per year). The nematodes Scottnema lindsayae and Eudorylaimus sp. were the most commonly found animal species, whereas rotifers and tardigrades were found only occasionally. On the highly trampled footpaths, abundance of S. lindsayae and Eudorylaimus sp. was up to 52 and 76% lower, respectively, than in untrampled areas. Moreover, reduction in S. lindsayae abundance was more pronounced after 10 years than 2 years and in the surface soil than in the deeper soil, presumably because of the longer period of disturbance and the greater level of physical disturbance experienced by the surface soil. The ratio of living to dead Eudorylaimus sp. also declined with increased trampling intensity, which is indicative of increased mortality or reduced fecundity. At one site there was evidence that high levels of trampling reduced soil CO(2) fluxes, which is related to total biological activity in the soil. Our results show that even low levels of human traffic can significantly affect soil biota in this ecosystem and may alter ecosystem processes, such as carbon cycling. Consequently, management and conservation plans for Antarctic soils should consider the high sensitivity of soil fauna to physical disturbance as human presence in this ecosystem increases.

Trampling on maritime Antarctica: can soil ecosystems be effectively protected through existing codes of conduct?

“…The generally accepted assumption is that disturbance effects on Antarctic soils are very long-lasting, especially in continental environments such as the Victoria Land Dry Valleys and Transantarctic Mountains (Campbell & Claridge 1987;Ayres et al 2008;Hodgson et al 2010). However, our data suggest that some areas of maritime Antarctic soil that have suffered intermediate levels of use could possibly physically recover after a period of as little as twoÁthree years without human presence.…”

“…Several impacts on soil biota have also been identified, the most obvious being reduction in vegetation cover and loss of vegetal biomass around paths (de Leeuw 1994;Pertierra et al 2013). Ayres et al (2008) observed reductions of up to 52 and 76%, respectively, in densities of two species of nematode, Scottnema lindsayae and Eudorylaimus sp., between paths with heavy pedestrian traffic and nearby undisturbed reference areas. Tejedo et al (2009) detected a clear decrease in Collembola abundance with increased pedestrian traffic, and Greenslade et al (2012) similarly noted large reductions in soil collembolan densities in areas on Deception Island subject to a high level of visitation relative to neighbouring undisturbed areas.…”

“…The consequences of pedestrian traffic vary according to the nature of the soils and vegetation being considered. In terms of soil structure and surface properties, trampling produces an increase in track width, penetration resistance and bulk density (Campbell et al 1998;Tejedo et al 2005;Tejedo et al 2009), micro-relief changes and visual impacts (Campbell et al 1998;O'Neill et al 2010), albedo alterations (Campbell et al 1994), and modifications in nutrient cycles including reduced soil CO 2 flux in some cases (Ayres et al 2008). Several impacts on soil biota have also been identified, the most obvious being reduction in vegetation cover and loss of vegetal biomass around paths (de Leeuw 1994;Pertierra et al 2013).…”

Microbiology of Eutrophic (Ornithogenic and Hydrocarbon-Contaminated) Soil

“…Soils around permanent bases can be intensely disrupted by building and heavy equipment use (Kennicutt et al 2010), while environmentally sensitive regions can be impacted by foot traffic (Ayres et al 2008). Trampling has been shown to impact invertebrate species and reduce CO 2 fluxes in Dry Valley soils (Ayres et al 2008), though specific affects on bacterial communities have not been investigated. Bacterial community structures may be altered by trampling due to disturbance of soil crusts, as has been demonstrated in other cold deserts (Kuske et al 2012).…”

Human Impacts on Soils

“…Nematode Scottnema lindsayae exhibited the greatest salinity tolerance of three species found in the Dry Valleys, with drier, more saline, and disturbed sites, being dominated by or solely occupied by S. lindsayae (Wall and Virginia 1999). Ayres et al (2008) compared nematode populations (abundance, ratio of living to dead individuals and dominant species) in tracks used continuously for 10 years during summer months with those used for 2 years. Ayres et al (2008) showed increased nematode mortality, lower abundances and a greater level of physical disturbance to the surface of tracks, which were used at higher intensities and at longer durations, compared with newer tracks and control areas.…”