Jen McComb

In 2001 scientists from the New South Wales National Parks and Wildlife Service (now Department of Environment and Climate Change), La Trobe University and an environmental consulting firm investigated a mysterious death of grass outside a cave in Australia’s Snowy Mountains. Heavy rains had washed dead bogong moths (Agrotis infusa) from the cave and grass touched by this outwash died. Investigations revealed that arsenic concentrated in the dead bogong moths poisoned the grass. Worryingly, arsenic occurred in the bodies or the droppings of three mammal species eating bogong moths, so arsenic contamination was spreading in the food chain. The arsenic came from the plains of Queensland and western New South Wales, where bogong moths breed in autumn (Figure 27.1). The grubs, called cutworm caterpillars, eat grasses and crops before pupating in the soil to develop into winged adult moths. Arsenic-based insecticides were used intensively in the early 20th century and some are still available, so cutworm caterpillars probably absorb arsenic when eating crops. The adults migrate to the Snowy Mountains, aestivating during summer in caves until cooler weather when they return to the plains (Figure 27.2). The bogong migration is amazing and inspirational, part of the natural legacy bequeathed by the Australian environment to its human occupants. By contrast, the moths’ residual arsenic toxicity is disturbing, showing how human intervention may squander or spoil rich natural assets. You are now, though, in a position to understand and to solve such environmental problems and to reflect on what the environment and its conservation mean to you. Chapter aims: In this final chapter we revisit the three case studies introduced in Chapter 1: Leadbeater’s possum, the crown-of-thorns starfish and the Corrigin grevillea. We show how theories and techniques described in this book are applied to these cases. To suggest what a career in environmental biology entails, we conclude with views from two eminent Australian environmental biologists. They describe the challenges of their careers and the changes in technology and in society’s attitudes they have seen.

About 40 years ago, the first comprehensive biology textbook written specifically for Australian students opened with the photograph in Figure 1.1, showing a flock of sheep in a paddock. The scene was typical of many agricultural areas in Australia then, and remains so today. The authors commented on the questions a biologist might ask when viewing the picture: why do the sheep prefer to stand in the shade? Why are there no sheep under the far tree? Why are there no young trees in the paddock? Today, these questions seem less relevant. A contemporary biologist might ask: what was the landscape like before the establishment of European agriculture? Are there signs of land degradation and, if so, how could they be reversed? Is the agricultural production sustainable? If not, what are the implications for local human communities? These questions reveal a growing concern about the impacts of expanding human populations and the application of new technologies on the natural environment. Chapter aims: This chapter describes how the stress of the world’s dominant animal species, humans, has severely altered biodiversity and natural ecosystems. Three in-depth examples of environmental problems are introduced, together with an explanation of the knowledge and skills biologists need to reverse or mitigate such problems.

Plant transformation is a key methodology that has allowed transfer and expression of novel genes for the improvement of economically important plant species as well as enquiry into deeper questions about the function of plant genes. For many plant species, stable transformation remains difficult or impossible. Where it is possible, there is usually a need for expensive resources such as laminar flow hoods, controlled environment growth rooms and highly skilled practitioners. In addition, there are often problems related to combining efficient plant regeneration with gene transfer as transfer techniques are carried out in undifferentiated cell cultures. Low transformation efficiency, instability of transgene expression, somaclonal variation and inability to regenerate whole plants are common problems.

This chapter describes the growth of root cultures from S. vulgaris, the production of pyrrolizidine alkaloid (PA) and the specific labelling of the compound in these cultures. Ideally, a final tissue mass of ~4 g is required for extraction and further processing. To obtain this, growth from a 200 to 250 mg stock for ~10 days is required. During this period, the culture is producing unlabelled senecionine, which will 'dilute' labelled alkaloid produced during a 24 h labelling period. If extremely 'hot' alkaloids is required for a specific purpose, it is suggested that roots be 'grown up' in an IBA-containing medium, promoting rapid root growth but little senecione production, and then placed in IBA-free medium for labelling. In this way, an even higher specific activity should be obtained. The manufacture of specifically labelled natural products in plant tissue culture in general, and roots in particular, will prove to be a very useful technique in toxic plant research.

Plants of dicotyledonous trees raised in tissue culture initially have many adventitious roots rather than the single tap root produced by a seedling. Little is known about the subsequent development of the root morphology of tissue cultured trees. Root architecture affects both survival after planting in the field and the likelihood of windthrow when trees are taller. The seedling tap root of eucalypts does not normally persist as the dominant root. Several lateral roots develop as sinker roots, grow to equal thickness and penetrate to great depths (Dell et al, 1989).

Introduction The importance of eucalypts and reasons for tissue culture Eucalypts are Australia's most distinctive plant group. They are contained within the genus Eucalyptus which consists of over 500 named species, with more as yet unnamed (Brooker & Kleinig 1983; 1990 Chippendale 1988). The natural distribution of the genus is almost completely confined to the Australian continent and Tasmania with only two species, E. deglupta and E. urophylla, occurring naturally in other countries. Since European settlement of Australia, seeds of eucalypts have been sent to countries throughout the world and they are now commonly grown in tropical and temperate areas for timber, pulp wood, eucalyptus oil, fuelwood, charcoal and as ornamentals. Exploitation of eucalypts outside Australia was initiated by the French. During the nineteenth century, eucalypts were planted in Europe and North America, and European imperial governments introduced them to colonies in South America, Africa and Asia. The presence of eucalypts in some of these countries is now so familiar to the native peoples that many consider them to be indigenous (Zacharin 1978). Although eucalypts in early plantations often grew very quickly the wood was sometimes of poor quality due to wood splitting and distortion (Clarke 1957; Penfold & Willis 1961; Pryor 1976). In many cases this was because the species chosen were inappropriate for local climatic and edaphic conditions (Evans 1980; Durand-Cresswell et al. 1982), the trees had been planted for the wrong purposes (Penfold & Willis 1961; Pryor 1976), or given incorrect fertilisers (Savory 1962; Stone 1968). The poor quality of the wood led to a slump in enthusiasm for growing eucalypts until about 1945 when world demand for pulpwood started to increase (Pryor 1976). Today the major uses of eucalypt wood are for fuelwood and pulpwood. There has been a 150 fold increase in pulpwood production from eucalypts since the early 1960s (Molleda 1984). They are now the most widely planted hardwood group in the world (Boland et al. 1984; Eldridge et al. 1993).