State of the Environment 2011 Committee. Australia state of the environment 2011.
Independent report to the Australian Government Minister for Sustainability, Environment, Water, Population and Communities.
Canberra: DSEWPaC, 2011.
At a glance
Organisms living in Antarctica have evolved to cope with severe events. However, it is challenging to measure their level of resilience and to predict how future climate change will impact Antarctic ecosystems because our understanding of key parameters is still limited, and with it our ability to assess adaptability, and hence resilience, of organisms and ecosystems.
To date, the question of the level of resilience inherent in Antarctic ecosystems has not received much attention because it is a complex concept and many parameters required to assess resilience are still unknown. The Scientific Committee on Antarctic Research produced a comprehensive review of the impact of climate change on the Antarctic environment in 2009, highlighting areas where knowledge is still lacking. Although marine and terrestrial ecosystems are now better understood than in the past, baseline data on biogeography and biodiversity are still scarce, as are fundamentally important long-term monitoring data.37 Researchers have only just started to investigate how organisms adapt to current climate change, and how resistant and resilient organisms and systems are.
For many, if not most, vertebrate species, important aspects of the dynamics of populations are either largely unknown or have been studied only at a few sites. Without comprehensive insights into variables, such as age of first reproduction, survival of different age classes, fecundity and the extent of emigration and immigration into and out of populations, as well as the drivers that influence these variables, we are unable to make long-term predictions about the viability of species in a changing environment. A thorough understanding of the ecological framework in which organisms live is also important when considering their resilience. For example, a number of Antarctic organisms live at South Georgia where the summers are up to 3 °C warmer than on the Antarctic Peninsula. Thus, the vulnerability of species needs to be determined on the basis of their ecological circumstances.37
Natural disturbances are part of life in Antarctic ecosystems and the endemic species are generally capable of surviving shock events because they have evolved strategies that allow their populations to rebuild after mass mortalities. Longevity among seabirds, and the ability of plant seeds to survive for long periods and to disperse, are among those strategies.
Shock events that test the level of resilience of a system occur in Antarctica just as they do in other parts of the world, ranging from intense storms affecting large areas to more localised incidents, such as scouring of the benthic environment by drifting icebergs (see Section 2.3.1). As long as these shock events are rare, communities can recover. However, increases in the magnitude and frequency of such events, as well as the duration of serious disturbances, are likely to become major challenges to the resilience of benthic communities. The slowest growing species may never recover if the interval between disturbance events is too short to develop and grow into mature organisms, whereas populations of fast-growing species may benefit if the competition for space, for example, is reduced.
We know that populations of some species of whales, seals and penguins have suffered human-induced mortality rates that pushed these species to the brink of extinction. Once hunting ceased, a number of species recovered; some, like king penguins, in a spectacular manner.226-227
However, these recoveries took place in a world where environmental conditions were not exposed to the rapid change that is currently under way. Today, a number of environmental components are changing rapidly (increasing sea temperatures, ocean acidification, higher intensities of ultraviolet radiation, etc.). The changes are complex and not always unidirectional, and there is currently little evidence on how the various factors are going to interact. There is no doubt that some organisms will benefit from these changes in the short term, but it is difficult to predict the effect of rapid climate variations on ecosystems. Many species may be vulnerable because their capacity to adapt operates at a much slower rate than the changes currently observed (see Section 3.1.1).
In the physical sciences, researchers are only just beginning to understand feedback loops and processes in the physical environment. Long-term monitoring data are also lacking in fields such as glaciology-particularly with regard to understanding changes in the active layer of the Antarctic ice sheet, as well as permafrost.37 The Scientific Committee on Antarctic Research recommends studies to further the understanding of the hydrological cycle and emphasises the need for improved estimates of the freshwater budget. Atmospheric sciences also need to address changes in the atmosphere's chemistry to improve the ability of models to predict the consequences of changes in ozone concentrations.37
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