Landscape rehabilitation in the Vestfold Hills
A ‘leave no trace’ philosophy can be successfully applied to geotechnical investigations in the Antarctic landscape.
The Vestfold Hills undulate on the edge of the Antarctic continent covering over 400 square kilometres. They consist of low-lying pale metamorphic bedrock, criss-crossed with a network of black dolerite dykes you would swear were someone’s attempt to play noughts and crosses on a continental scale. Spread over this patterned rock in patches of various thickness lie drapes of mud, sand, gravel and boulders (some as big as caravans) that have been dumped by the retreat of the Antarctic ice sheet that covered the area during numerous ice ages. At first glance, this landscape of loose, jagged, poorly sorted glacial till (or moraine) could be mistaken for Mars, with no trees or bushes; nothing but salt encrusted soil and barren rocks.
Nestled on the edge of these hills overlooking the island-dotted Prydz Bay is Davis station, established in 1957 by Phillip Law (then Director of the Australian Antarctic Division). Ever since Davis and Australia’s two other Antarctic stations (Casey and Mawson) were established, investigations into the most practical and cost effective way to access them have ensued. These include investigations into the possibility of landing small fixed-wing aircraft in Davis’s back yard.
Aircraft remain vital to supporting activities in Antarctica and there is a continuing need to look for ways to improve the safety and reliability of aviation operations. Since the 1960s, several investigations have been carried out literally to test the ground around Davis. During the early 1980s, in particular, there was a concentrated effort to perform site investigations, which involved excavations by heavy machinery that pushed up soil mounds, dug pits and pushed boulders aside to make access paths through the area. Back then, it seems disturbing the landscape was not considered a serious issue and no efforts were made to tidy up afterwards.
Today you can still see pits, mounds, excavator tracks and cleared paths that have persisted for over 30 years. There is no rain to wash the evidence away or wear down the mounds and ruts. Instead, the landscape is scoured by wind, with occasional flooded patches from melting snow banks. Preservation of these earthwork features appears to depend on the cohesion of the sediments affected. Sandy, non-cohesive sediment shows redeveloped desert pavement in most settings, with excavations and tracks defined by the unnatural distribution of boulders. Clayey, cohesive sediment preserves wheel ruts and some imprints of excavator tracks.
In 2012–13 another small scale geotechnical investigation was carried out in some of the same areas as before, but this time disturbance to the ground was managed sensitively. Every effort was made to remediate all sites, to remove any evidence of activity. Excavation was mostly restricted to hand digging and auguring to avoid the use of heavy machinery, however an excavator and machine auger were used on existing roads where there was pre-existing disturbance. For all excavations a simple yet effective method was devised, with the material removed being carefully placed on boards next to the holes, keeping the stratigraphy (layering) in correct reverse order. This meant that when the samples had been taken and ground features logged, the material could be replaced in the hole in correct order, thereby retaining original material colour and grading. Some careful raking and smoothing of the surface, and replacement of larger rocks to their original position, resulted in no detectable disturbance.
To assess the recovery of these minor excavations each site was inspected 12 months after disturbance. Pleasingly, there was only minor evidence at some sites, only noticeable to a trained eye looking for evidence. It is doubtful these minor disturbances would be detected by anyone wandering past without prior knowledge of the activity; in fact, the observer would probably leave more impact with their own footprints.
These investigations reveal some interesting changes in attitude to environmental management. The Antarctic Treaty (Environment Protection) Act of 1980 was in effect for both investigations, but at some point between then and now our attitude to this pristine glaciated environment has matured into a respectful responsibility. Every activity approved in the Australian Antarctic Program must seek and gain environmental authorisations and/or permits through the Antarctic Treaty System before environmental disturbance can be performed. As part of this process each activity is scrutinised for recovery procedures and mitigation processes to ensure the human ‘footprint’ in Antarctica is kept to a minimum.
The question remains whether remediation of the old workings is feasible, when it is no easy task to access these areas and doing so may well create more disturbance than is there already. However, with good planning and adherence to technique and process, as evidenced by the activities outlined above, it is possible to ensure that impacts are minimised or negated altogether.
Dr Barbara Frankel
Antarctic Modernisation Program