Assessing feral animal impacts on World Heritage sub-Antarctic Macquarie Island
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Date
2019-07-30
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International Union for Quaternary Research (INQUA)
Abstract
Animals introduced by human activities to remote islands can be ecologically devastating as they often have a large proportion of endemic species with limited resilience to non-indigenous ones. Sub-Antarctic islands are remote, small islands in the vast Southern Ocean. Most have experienced some form of impact from non-indigenous fauna (e.g. rabbits, rats, mice, cats) that became feral pests soon after their deliberate and unintended introductions. Conservation and management efforts are increasingly focused on their control and/or eradication.
World Heritage UNESCO Biosphere listed Macquarie Island (54°S) is one of the most impacted sub-Antarctic islands, in particular due to the introduction of rabbits in 1879, to the extent that its World Heritage values were considered threatened in the early 2000s. The values relate to Macquarie Island’s geological, geomorphic and physiographic features, and exceptional natural beauty and aesthetic importance. The latter includes the presence of a large number of lakes, tarns and ponds, and extensive peat beds.
The largest rabbit and rodent eradication program for any sub-Antarctic island was undertaken from 2010-2014. Monitoring to assess recovery focused on geomorphological (including erosion) processes, vegetation and some fauna (i.e. invertebrates, burrowing petrels and albatross species) using previous studies as baselines. All of these studies were undertaken after rabbits were introduced, and no pre-introduction data exist beyond some limited historical documents after its discovery in 1810. No monitoring to assess recovery of the lakes, tarns, ponds or peat beds was undertaken.
In the absence of long term data, palaeoecology may be used to determine the nature, magnitude and spatial extent of impacts in the context of long term natural variability. To provide a long-term context for assessing the island’s pre-invasion state, invasion impacts, and to provide baseline information for the waterbodies, we undertook a palaeoecological study using high-resolution x-ray fluorescence scanning and hyperspectral imaging together with biological (diatoms), geochemical (total organic carbon and nitrogen) and sedimentological (grain size) analyses of lake sediment cores in two different areas of Macquarie Island.
Results showed that Macquarie Island lakes have undergone unprecedented and statistically significant environmental changes since the introduction of rabbits in 1879. Sediment accumulation rates increased by more than 10 times at one site, 100 times at another, due to enhanced catchment inputs and within- lake production. Total organic carbon and total nitrogen contents of the sediments increased by a factor of four. The diatom flora became dominated by two previously rare species in both lakes.
This study provides an example of how palaeoecology may be used to determine baseline conditions prior to the introduction of non-indigenous species, quantify the timing and extent of changes, and help identify a basis for monitoring the recovery of waterbodies following successful non-indigenous species eradication programs
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Keywords
Animals, Wild animals, Australia, Tasmania, Islands, Humans, Rabbits, Mice, Cats, Pest control, Peat, Lakes
Citation
Saunders, K. M., Roberts, S. J., Butz, C., Grosjean, M., Hodgson, D. A. (2019). Assessing feral animal impacts on World Heritage sub-Antarctic Macquarie Island. Poster presented to the 20th INQUA Congress (INQUA 2019), Dublin, Ireland, 25th - 31st July 2019. Retrieved from: https://virtual.oxfordabstracts.com/#/event/public/574/submission/1543