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	ECOS Issue 74

Stem-borer with promise
A hopeful sign has emerged in the battle to control one of Australia's worst plant pests, the giant sensitive plant (Mimosa pigra). A stem-boring moth, released as a potential biological control agent in 1989, appears to be causing large reductions in its seed production. M. pigra, a native of Central and South America and a pest in Asia and Africa as well as Australia, has spread rapidly in the wetlands south and east of Darwin since the 1970s.
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Flood control by ants
Mulga ants are curious members of the genus Polyrhachis, which occurs widely throughout Australia, the Orient and the Middle East. They are invariably associated with the grey-green shrubs of mulga (Acacia aneura), and their odd, circular nests are a common sight on the hard-packed red earth of central Australia. Two similar species of mulga ants inhabit the area north of Alice Springs, each of which surrounds its nest with a distinctive circular 'fence' of mulga phyllodes. Because the red earth of the centre does not readily absorb water, it is suspected the mulga ants build miniature levees simply to prevent their nests flooding during arid Australia's infrequent heavy rains.
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Preserving biodiversity
Three Australian scientists are among a team of 25 from around the world who have embarked on the daunting task of preparing a strategy for preserving global biodiversity. The strategy document will address questions ranging from what actually constitutes biodiversity to how to achieve sustainable development while protecting the diversity of plants and animals. It will spell out what needs to be done in the areas, among others, of gathering more information about what species exist where, providing access to this information and developing computer-based systems for ready assessment of the effects that proposed developments will have on species diversity.
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Environmental weeds - a massive problem Ranging from rainforest-strangling vines to grasses that can choke wetlands, introduced plants that have established themselves in the wild have become a major threat to the environment. This article looks at the most prevalent weeds and outlines the steps which are being undertaken to control them. Download Article

Sustainability and the pastoral industry A survey of producers, advisers, scientists, environmentalists and others has revealed big differences in perceptions of land degradation and the prospects for achieving sustainable grazing. Download Article

Unravelling the climate-change conundrum
In 1967, an American research vessel, Eltanin, completed an oceanographic survey across the Pacific Ocean between Australia and Chile, collecting water samples from the ocean's interior. The 'Scorpio cruise', as it is known, measured temperature and salinity levels in ocean waters from the near-surface to depths below 4.5 kilometres. More than 20 years later, the CSIRO research ship, RV Franklin, retraced part of the earlier cruise, collecting water samples at 72 sites across the Tasman Sea. The findings were striking - the first firm evidence of climate change in the Southern Ocean, perhaps due to the enhanced greenhouse effect. The follow-up survey found evidence of warming in the oceanic interior, a rise in sea level and changes in salinity suggestive of surface warming in the Southern Ocean.
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Climate models - for clues to the future
Computer simulations or numerical models of climate are tools of the meteorologist and oceanographer - tools that generate no reality beyond the virtual, yet capable of revealing deep complexities in nature. Such models comprise the engine of research into climate variability and change. Yet, despite their importance and success today, climate models are highly artificial and severely limited in their resolution, or degree of detail. Research groups around the world are working to improve the predictive capacity of the models and are reporting some successes. Researchers at CSIRO's Division of Atmospheric Research appear to have identified the source of some of the simulation problems, and found ways to improve resolution.
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Through thick and thin - the problem of clouds
Clouds reflect 20 per cent of the sunlight entering the atmosphere, making them a crucial factor in the enhanced greenhouse effect. But their role is not simple: they also absorb sunlight and infrared radiation from the surface, release heat when they produce rain, alter their optical properties in response to pollution, emit radiation into space and influence the concentration of a major greenhouse gas, water vapour. In order to find out more about the internal structure of clouds, three CSIRO climate groups are planning a Southern Ocean cloud experiment, to be conducted off Tasmania's west coast in mid 1993 and early 1994.
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The problems that life presents
Uncertainties are never more certain than when atmospheric science tries to take account of the biosphere. A small change or fluctuation in the rates of biological processes can have a significant impact on the concentration of carbon dioxide and other greenhouse gases in the atmosphere. An increased atmospheric concentration of carbon dioxide itself can speed up the rate at which plants absorb carbon - a result called the carbon dioxide fertilisation effect. But little is known about the strength of this effect on a global scale.
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Changing weather
Estimates of the regional impacts of global warming are perhaps the most sought-after outcomes of climate-change research, and the predictions provide a stark reminder of what is at stake in the greenhouse debate. Climate scientists around the world are making progress in removing the large uncertainties involved in predicting the regional and local effects of global warming, but in the process have found the effects more complex and challenging than previously thought. The possible impact of climate change on natural ecosystems is of grave concern to biologists. Using CSIRO model scenarios of climatic change, zoologists at the Victorian Department of Conservation and Environment have devised 'bio-climatic range' maps of Victoria and estimated the ecological impact on 42 native animal species (about 6 per cent of the State's vertebrate species).
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Getting to know the brain New imaging techniques should increase understanding of changes in the brain associated with neurological and psychiatric disorders. This article looks at existing methods and summarises their techniques and limitations. Download Article

More wood from plantation trees Ways of working out how climate change may affect tree growth and what impact forests may have on the build-up of atmospheric carbon dioxide are among spin-offs from a major study of the biology of forest growth. Download Article

A climate for better models
The biggest game in climate research today is building the best numerical models of the global atmosphere. The validation of models is, of course, a serious business, especially as governments increasingly rely on them in making important and potentially costly policy decisions concerning abatement of climate change due to the enhanced greenhouse effect. In a new study, CSIRO's climate impact group compared the performance over the southern and South-East Asian region of four leading models.
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