It is not bombastic of me to claim that Antarctica stands as the last great untouched wilderness on the planet. It has remained geographically and biologically isolated from the rest of the globe for millennia. Antarctica does have its very own unique flora and fauna that have persisted in the region since the breakup of the Gondwanan supercontinent over 30 million years ago. Most of this biodiversity is to be found on small slithers of ice-free habitats on the edges of the continent and on a scattering of islands. As a result of climate change and increasing human activity in the region however, these very simple ecosystems are at an ever-increasing risk of alien species colonisation.
For more than a century humans have been visiting the Antarctic continent: first the whalers, then the explorers and scientists, and now the tourists. Nearly 50,000 tourists visited the Antarctic continent last year, compared to less than 5,000 research personnel. Our human footprint in the wilderness is growing.
The consequences of our presence are in the literal footprints we leave. The cold environment means that moss rarely springs back when trodden on, leaving signs of damage for years. In the ‘pristine’ McMurdo Dry Valleys, a place so ancient and harsh it is used as an analogue for Mars, a human footprint can remain in the soil for a lifetime. Vehicle tracks from the 1970s still persist today.
Now we find that research activities and visitation have led to more than marks in the moss, they have lasting ecological consequences. Unwittingly we carry seeds, spores and invertebrates with us, despite biosecurity campaigns. On the Antarctic peninsula, an alien grass is spreading faster than it can be removed. This in a land where there are only two species of vascular plant. Whilst on islands along the Antarctic Peninsula, a winter crane fly has taken up residence in several research stations and has even been seen flying outside. But of all the introductions to Antarctica, it may be something flightless that can cause the most change.
During a 1960s research experiment, small larvae of the midge Eretmoptera murphyi were accidentally introduced to Signy Island in the South Orkneys (600km north west of the Antarctic Peninsula). Its presence on Signy makes it the largest terrestrial organism on the island, such is the simplicity of Antarctic ecosystems. The midge is flightless, asexual and feeds on dead organic matter, of which there is a great abundance on Signy in the form of peat forming moss banks. As these larvae eat through the peat not only do they change its composition, but their sheer abundance (150,000 m2 in places) is also changing the soil chemistry too: at times it can increase nitrogen levels so much that the fertilisation input is equivalent to that of seal colonies. As this midge is asexual, only one individual was needed to start the new colony. Likewise, only one more would need to be moved elsewhere to establish on another island, or even the Antarctic Continent.
A recent article in the Guardian highlighted the issue of single invasive species, even in complex ecosystems, where the intricate food webs can act as a buffer. Andrew Cox of the Invasive Species Council argued that invasive species are becoming a larger driver of species declines than habitat loss and climate change. If we are to remotely hold ourselves accountable as perhaps the greatest invasive species of all, then Antarctica is one of the few places left where we can demonstrate responsibility. Without Antarctic science we would not have learnt the lessons of ozone damage, of climate change and of many elements of ecosystem function. And now we are learning the cost of invasions at a fundamental level – the ability of a single species to terraform. I hope that we can continue to visit the continent to learn more about our planet; what it teaches us is invaluable. But I also hope that the lessons we learn will be taken seriously by all those who visit, and applied not just to Antarctica, but to all ecosystems: that we must tread lightly, wherever we go.
References:
- Bartlett JC, Convey P, Hayward SAL (2018) Ecological consequences of a single introduced species to Antarctica. British Ecological Society Annual Meeting 2018, Birmingham, UK.
- Council of Managers of National Antarctic Programs (COMNAP)
- Guardian Article, 20 January 2019
- Hughes, K.A., Worland, M.R., Thorne, M., Convey, P., 2013. The non-native chironomid Eretmoptera murphyi in Antarctica: erosion of the barriers to invasion. Biol. Invasions 15, 269–281.
- International Association of Antarctica Tour Operators (IAATO) 2018 Visitor Numbers
- Molina-Montenegro, M., Carrasco-Urra, F., Rodrigo, C., Convey, P., Valladares, F., Gianoli, E., 2012. Occurrence of the non-native annual bluegrass (Poa annua) on the Antarctic mainland and its negative effects on native plants. Conserv. Biol. 26, 717–723.
- Volonterio, O., de León, R.P., Convey, P., Krzeminska, E., 2013. First record of Trichoceridae (Diptera) in the maritime Antarctic. Polar Biol. 36, 1125–1131.