Polar explorers: natives and invasives in Antarctica
Nomenclature is fundamental to ecology and natural history: tying, describing and sorting an individual, species or habitat to a particular category or definition. The idea of what constitutes a ‘native’, ‘non-native’ or ‘invasive’ species is a thorny issue that we’ve touched on before. The words themselves are highly loaded with (largely unhelpful) meaning, association and history.
To paraphrase Stephen Jay Gould, species have been migrating, colonising, evolving and going extinct for millennia. It is only by a particularly unpredictable cocktail of time, place and chance (and of course, human perception and classification) that a species develops its ‘native’ environmental distribution.
To look at it this way, ‘alien’ species have always been ‘invading’ new environments through history, creating new and ‘novel’ ecosystems. Indeed, a huge amount of funding (including through BioFresh’s work on freshwater ecosystems) is currently being diverted towards understanding how species will be able to migrate and shift their range as a means of adapting to future climate change scenarios.
Human influence on introductions
Of course, the distinction we have to make is whether humans are involved in artificially transporting organisms from their normal environments to new ones. In this scenario, the ‘invasive’, ‘alien’ species has the potential to cause huge controversy, as ecosystem function is disrupted, and native species potentially become extinct (see for example, the introductions of American signal crayfish in the U.K., or the Nile Perch in Lake Victoria). But even thinking about human agency in introducing species is difficult: should we differentiate between when this is intentional (e.g. importing pets or exotic plants) and when it is not (e.g. through transport systems – like the round goby in ship ballast water)?
Understanding how to define (and consequently manage) a ‘native’ or ‘non-native’ species isn’t clear cut. Knowledge of past environments – whether through fossil, pollen or diatom records – can throw up surprises. There are cases where a species thought to be native is shown to be a relatively recent arrival (as Charles Warren (2007) states: “in a recent book celebrating 100 Heritage trees of Scotland (Rodger et al., 2003), no fewer than 42 are aliens” ) or where a species thought to be non-native is actually an extinct native (e.g. Kathy Willis and team’s work on the Galapagos islands)! This idea loops back to the importance of nomenclature and definitions in ecology and environmental management. The presence of a ‘native’ or ‘non-native’ species is very powerful in influencing appropriate management of an environment.
Determining the native/non-native status of newly discovered terrestrial and freshwater species in Antarctica
A soon to be published paper in the Journal of Environmental Management by Kevin Hughes and Peter Convey from the British Antarctic Survey touches on these debates as it attempts to determine the native/non-native status of newly discovered terrestrial and freshwater species in Antarctica. The onset of scientific research and tourism in the latter half of the twentieth century have placed Antarctica’s ecosystems under increased risk of colonisation by non-native species.
In June 2009, researchers discovered two unusual, previously undocumented plants growing in Whaler’s Bay on Antarctica’s Deception Island. Both plants (N.magellanica and Gamochaeta nivalis) are common on the southern tip of South America, so their seeds may have been transported by natural means (e.g. wind or bird dispersal). However, Whaler’s Bay is a busy port for industry, research and tourism, so it is possible the plants were introduced (intentionally or not), by humans.
How should the plants be categorised? Native or not? Comprehensive biodiversity surveys have only been carried out at a small number of locations. Hughes and Convey discuss how, because of this lack of data to guide scientists and environmental managers in Antarctica, it is difficult to determine the native/non-native status of any newly discovered species. The species in question has the potential to be one of:
a) A previously undiscovered long-term native species
b) A recent natural colonist
c) A human-influenced introduction.
Under the Antarctic Treaty, the environmental management implications of this uncertain nativity are important. The Treaty gives a clear duty for signatory parties to protect and conserve natural species and ecosystems in Antarctica. A major part of this obligation is to eradicate and control the introduction of non-native species to the continent. But, based on a lack of comprehensive biodiversity data for the continent, how can managers implement a Treaty which stresses the value and importance of native species and ecosystems?
Criteria for categorisation
Hughes and Convey give a range of criteria for assessing the native/non-native status of a newly discovered species. This criteria includes looking at historical evidence (fossil record and historical biodiversity surveys), current species status and distribution (is the species in disturbed habitat close to a possible introduction site), genetic diversity and reproductive patterns. However, all this categorising requires a lot more research to generate the necessary biological data, a difficult process is such harsh, demanding environments.
Freshwater ecosystems in Antarctica are generally dominated by cyanobacteria along with populations of cyanophytes, bacteria, yeasts, rotifers, nematodes and diatoms. As yet, there are no documented freshwater fish, mammals, invertebrates or molluscs – whether native or non-native. As such Hughes and Convey only touch on freshwater ecosystems. However, it is perhaps worth considering how the freshwater ecosystem assemblages in Antarctica may be influenced by climate change. Would there be more freshwater ecosystem niches available? How might these be exploited by introduced species?
Management and Antarctic geopolitics
It is important to also consider the fascinating, piecemeal geopolitical division of Antarctica by different nations staking a claim to a continent run free of national political influence through the Antarctic Treaty (a process that has – amongst other geographical and political quirks – led to a golden statue of Lenin being placed in the middle of the continent, facing Moscow). Co-ordinating large-scale environmental management across Antarctica under a Treaty which doesn’t give a nuanced understanding to what constitutes a native species may prove difficult.
Some conclusions: determining nativity
Hughes and Convey’s work demonstrates just how important nomenclature and categorisation are to environmental management. Determining what constitutes a native and non-native species in Antarctica’s sparse, largely-untouched and unique ecosystems would at first appear to be relatively straightforward. However, a lack of comprehensive, large-scale biodiversity data coupled with increased traffic to and from the continent means that making the native/non-native distinction is potentially tricky. And this becomes very important when nativity underpins the Antarctic Treaty’s approach to environmental management.
A common theme we regularly touch on here is the need for more detailed and comprehensive biodiversity data to inform environmental policy and management. However, even with a comprehensive understanding of past environments, how do we determine what is and what isn’t a native species? Where (and why) should a particular historical baseline for nativity be set? These are important questions that will run and run…!
Hughes, K., & Convey, P. (2012). Determining the native/non-native status of newly discovered terrestrial and freshwater species in Antarctica – Current knowledge, methodology and management action. Journal of Environmental Management, 93 (1), 52-66 DOI: 10.1016/j.jenvman.2011.08.017