One of the main values of Antarctica for science is the near-pristine environment where clean media (air, snow, ice, sediments) offer unique opportunities for many research activities such as astronomical and astrophysical observations, geophysical and ecophysiological studies, and investigation of the Earth's magnetosphere and ionosphere. Antarctic environmental matrices represent ideal archives of data on past and current trends in global processes and, in particular, the long-range transport of persistent atmospheric contaminants. The Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for protection of the Antarctic environment, of its value for scientific research and of its wilderness and aesthetic values. The standards of protection set in these guidelines for Antarctica are generally higher than those required for other parts of the world. However, as discussed in this book, the effective conservation of the value of Antarctica for scientific research requires better knowledge of the structure and functioning of ecosystems, and the development of long-term monitoring programmes on a continental scale to detect changes induced by climatic or anthropogenic perturbations. All human activity in Antarctica (e.g. scientific research and associated logistic support, fisheries and tourism) causes localised environmental pollution and large-scale impacts (e.g. air pollution by aircraft and ships, accidental spillage of oil or fluids from ice drilling operations,waste materials, and thousands of released weather and research balloons which land on the continent or in the sea). The application of the Protocol on Environmental Protection will help minimise some of these impacts, especially near scientific stations. However, the data reported in the previous chapters show that most persistent airborne contaminants in Antarctica and the Southern Ocean mainly originate from anthropogenic sources in the Southern Hemisphere. Although current levels of environmental contamination do not represent a great threat to the sustainability of terrestrial and marine ecosystems, it can not be excluded that climate change, together with increased inputs of some atmospheric contaminants, may compromise the scientific value of the Antarctic environment.

In the last century, most economical and industrial development took place in the Northern Hemisphere, where several countries grew rich while inadvertently burdening the global environment. However, the global pattern of anthropogenic emissions of persistent atmospheric contaminants, greenhouse gases and aerosols is changing rapidly. Most of the world's future population growth will occur in countries of the Southern Hemisphere, and this growth will necessarily determine an increase in the magnitude of production and resource exploitation. If rich countries in the Northern Hemisphere do not adequately help (through financial aid and transfer of technologies) developing nations to address new environmental threats, many of these nations will improve their overall standard of living following historical consumption and production practices.As a result, anthropogenic impacts on the climate and environment of the Southern Ocean and Antarctica may significantly increase in the near future. Although the international community has set these regions aside for protection as natural reserves and areas for the conduct of scientific research (through the Antarctic Treaty in 1961 and the signing of the Protocol on Environmental Protection to the Antarctic Treaty in 1991), wider international agreements will be necessary to address environmental challenges facing Antarctica in this century. Without the inclusion of new participants at all levels of the decision-making process for coordinated global action, and adequate financial support and technological innovation in developing countries, the Protocol to the Antarctic Treaty will probably not be adequate to effectively protect the Antarctic environment. However, problems such as the need for more intensive international cooperation among nations and people are beyond the scope of this book. Its aim was to give a general overview and a frame of reference of the distribution and cycling of natural elements and persistent contaminants between the atmosphere, snow, seawa-ter, and organisms in Antarctica and the Southern Ocean. Reported values can be used as baselines to assess future variations in the environmental distribution of trace metals and persistent organic contaminants. This concluding chapter briefly discusses possible future trends in the environmental contamination of Antarctica, and suggests research activity and long-term monitoring approaches to improve the efficiency and cost effectiveness of programmes for the protection of the Antarctic environment and its scientific value.

The critical role of long-term, broad-scale studies and programmes to monitor changes and trends in global environmental systems has been acknowledged by major scientific initiatives such as the International Geosphere-Biosphere Program (IGBP) and the Long Term Ecological Research Network (LTER, implemented by the US National Science Foundation). The LTER network was established in 1981 in view of the fact that eco logical processes must be studied for much longer periods than normally foreseen by most research grants. The network for long-term research on ecological systems has grown rapidly over the last two decades. In 2001 it included 24 sites ranging from the tropical rainforest of Puerto Rico to the northern Chihuahuan Desert of New Mexico. Access to data collected at each site, the diffusion of knowledge and of approaches to policy-making and management, and public understanding are integral parts of the LTER programme. Two polar sites are located in Antarctica - the one in the pelagic marine ecosystem at Palmer Station (Antarctic Peninsula), the other in the McMurdo Dry Valleys (southern Victoria Land). The Palmer LTER site essentially focuses on interactions among regional climate, hydrography and pack ice, and on the impact of variations in the extent of sea ice on the most representative marine pelagic species. The results of research on ecological processes in the western Antarctic Peninsula are also reported in a book by Ross et al. (1996). The McMurdo LTER site was established in 1994 with the aim of acquiring integrated knowledge of biological, chemical and physical factors involved in biogeochemical processes affecting the largest cold desert of continental Antarctica. Several publications on various aspects of this region have been cited in previous chapters. However, for a more comprehensive presentation of the results of ecological research in the McMurdo Dry Valleys, the reader can refer to the book edited by Priscu (1998). Other books have recently been published on ecosystem processes and protection of the Antarctic environment (e.g. Lyons et al. 1997; Hansom and Gordon 1998; Davison et al. 2000; Huiskes et al. 2003).

Having presented an overview of current knowledge on the occurrence and cycling of persistent contaminants in Antarctic ecosystems, it seems appropriate to conclude this book with possible future trends in environmental contamination and suggestions on possible approaches to monitoring of environmental change. Predicting how climate change and human activity in the Southern Hemisphere will modify contaminant transport and deposition in Antarctica and the Southern Ocean is an exceptional challenge. Although the biogeochemical cycles of trace metals and physico-chemical properties of most POPs are rather well known, knowledge of past and future trends in climate variability, of sources and pathways of persistent contaminants, and of environmental processes in Antarctica and the Southern Hemisphere is still very inadequate to delineate possible future scenarios for these regions. This chapter only attempts to outline observations and projected changes in the climate and atmospheric contamination of the Southern Hemisphere, with the aim of foreseeing the possible impact of persistent contaminants in Antarctic ecosystems and suggesting possible approaches for the early detection of environmental perturbations.

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