Denis A. Saunders

Why have birds in the woodlands of Southern Australia declined

This paper reviews the reasons why so many species of birds have declined in the eucalypt woodlands and associated habitats across the agricultural zone of southern Australia. The extent of habitat lost, over 90% in some regions, has led to the local extinction of some bird species, simply through random sampling effects. Habitat specialists and those that move sequentially among several habitats, are especially at risk, as some habitats have been lost disproportionally. Fragmentation introduces additional problems by subdividing populations into small, isolated sub-populations. Whereas some of the remaining species of birds appear able to move through highly fragmented landscapes, it is possible that they suffer high mortality while doing so. Some species that have been lost regionally may have had difficulty dispersing, but there have been few detailed studies of the demography of Australian birds in fragmented landscapes. Such studies are necessary before we can assess the value of corridors, or other means, to assist dispersal of birds. Fragmentation also leads to edge effects, which, when compounded by habitat degradation, may alter the intensity of a number of ecological processes. There is circumstantial evidence suggesting that loss of nest sites and increased predation on nests and free-living birds have contributed to the decline of woodland birds. Increased interspecific competition, for instance with noisy miners Manorina melanocephala, may also have a major impact on smaller insectivores and honeyeaters. Effects of parasites and disease have barely been studied in Australia, though brood parasitism could account for local losses. Dieback of eucalypts and loss of understorey are common in fragmented and degraded landscapes and are associated with a greatly reduced diversity of birds. The effect of fragmentation and degradation on food has received minimal attention. We propose further research that tests the importance of some of these ecological processes in causing the decline and loss of bird species in agricultural woodlands. Although management should proceed immediately, including a cessation of any further clearing of native vegetation, it should be conducted in conjunction with research. We suggest how the findings of research can inform managers, which will make management more effective in achieving conservation of regional avifaunas.

Changes in the Avifauna of a region, district and remnant as a result of fragmentation of native vegetation: the wheatbelt of western Australia. A case study

Abstract The wheatbelt of Western Australia is an area of about 140 000 km2 which has undergone massive changes since European settlement in 1827. Clearing of native vegetation for agricultural development has removed up to 93% of the original vegetation in some areas and replaced it with exotic grasses, cereal crops and frequent watering points. The remaining vegetation is made up of thousands of remnants of various sizes, shapes and degreees of isolation scattered across the landscape. The avifauna of the wheatbelt is examined at the regional level, the district level and at the level of the individual remnant and changes over the last 80 years or so are described. Two species of bird have gone extinct in the wheatbelt out of 148 species of land birds recorded in the region over the last 80–90 years. At the district level, more species have become extinct, the numbers depending on the extent of the removal of native vegetation and length of time since clearing took place. There is demonstrable loss of bird species at the level of the individual remnant; in the example cited (81 ha) three species have gone extinct over the last 10 years. This rapid loss of species from district avifaunas means that remnant vegetation needs to be retained intact and conservation agencies should develop assessment techniques to identify reserve networks which include the species that have declined so that management can concentrate on them. Priorities for management should then be developed and local communities involved in the management of their local conservation systems or networks.

Species survival in fragmented landscapes: where are we now?

We present a brief introduction to current attempts to understand and mitigate the effects of fragmentation on species survival. We provide a short overview of the contributions of empiricists, modellers, and practitioners in this issue of Biodiversity and Conservation, which were initiated during a workshop held in Australia in February 2002 on the topic ‘Species Survival in Fragmented Landscapes: Where are we now?’. These contributions address the themes ‘uncertainty in research and management’, ‘tools for quantifying risk and predicting species sensitivity to fragmentation’, and ‘tools for reassembling fragmented landscapes’. A final contribution provides a synthesis across the contributions and highlights the most important areas for future research on species survival in fragmented landscapes.

The Kellerberrin project on fragmented landscapes: A review of current information

Abstract Overall, the wheatbelt of Western Australia occupies 14 million ha and has had 93% of its native vegetation removed over the past 100 years, much of it disappearing within the last 50 years. This rapid and extensive clearing, together with the introductions of exotic and Australian endemic species to the region, have resulted in a significant loss of native species—both plants and animals. The vegetation which remains is present as small remnant patches. The resulting collection of remnants significantly under-represents several of the major vegetation types. In addition, many of the remnants are severely degraded as a result of grazing and other disturbances (such as nutrient enrichment and other impacts from surrounding agricultural lands), and species are still being lost. The Kellerberrin area is the focus of a study by CSIRO Division of Wildlife and Ecology into the conservation potential of remnants of native vegetation and the options available for their management. The study has centred on a 1680 km 2 area and examines the structure and dynamics both of individual remnants and of remnant networks within the agricultural matrix. Without active management, many remnants will be unable to continue to support native plant and animal communities. Management must be based on existing information and refined as more data become available. Research and management must, therefore, interact strongly.

Problems of survival in an extensively cultivated landscape: the case of Carnaby's cockatoo Calyptorhynchus funereus latirostris

Abstract The south-west of Western Australia has undergone recent and extensive clearing of its native vegetation to develop agricultural enterprises. In some areas, over 90% of the original vegetation has been removed and the remainder is scattered in numerous patches of varying size, shape, degrees of isolation and degradation. There have been marked changes in the distribution and abundance of the avifauna of this area, with some species disappearing from parts of their former range and others expanding their ranges to take advantage of the altered landscape. Carnabys cockatoo Calyptorhynchus funereus latirostris is one species which has suffered widespread decline in numbers as a result of the fragmentation of its former habitat and it no longer occurs over a significant portion of its former range. The extensive removal of native vegetation, patchy distribution of food and interactions with species like the galah Cacatua roseicapilla and man are contributory factors to its decline. It is pointed out that some local disappearances of this species may have been avoided if corridors of native vegetation had been left across the landscape to link remnant patches. These could have channelled Carnabys cockatoo to areas of native vegetation which provide its food. Not only is it important to retain linkages between remnants of native vegetation but there is a need to re-establish corridors of native vegetation in extensively cleared agricultural areas such as those in the wheatbelt of Western Australia.

Integrated landscape ecology: A Western Australian perspective

Abstract The wheatbelt of Western Australia now has severe nature conservation and agricultural problems resulting from rapid and excessive clearing of native vegetation. The landscape is comprised of a large number of small remnants of native vegetation within an agricultural matrix. Currently, different segments of the landscape are managed virtually in isolation, despite the functional interdependence of these elements. Fragmented management of the landscape means that neither conservation problems or agricultural land degradation can be tackled adequately. Similarly, management of conservation networks is rendered difficult. We suggest that management has to be integrated across the landscape, and that complementary strategies can be evolved which simultaneously meet the objectives of conservation and production management. Revegetation for the reduction of land degradation such as salinisation, waterlogging or erosion can also benefit nature conservation. Enhancement of existing conservation networks is possible using this strategy, which can be incorporated into the farm planning process. To be successful, integrated landscape planning and management must be carried out by the local human community, with expert guidance but not interference from government agencies. The situation in the Western Australian wheatbelt has relevance in most other parts of the world where conservation and production needs have to be balanced.

Changes in a remnant of salmon gum Eucalyptus salmonophloia and York gum E. loxophleba woodland, 1978 to 1997. Implications for woodland conservation in the wheat–sheep regions of Australia

Abstract The condition of salmon gums Eucalyptus salmonophloia with large hollows in them in a 15-ha patch of remnant salmon gum-York gum E. loxophleba woodland in the northern wheatbelt of Western Australia was examined in 1978. The patch was an important breeding area for six species of cockatoo, including two endangered species. The patch was revisited in 1981 when the condition of all 682 salmon gums and York gums in the patch was examined and each was measured and photographed. A further visit was made in 1997 when the condition of the surviving trees was examined and each was again measured and photographed. The condition of the trees at each visit was classified as “good”, “staghorn”, “broken top”, “dead” or “fallen.” Over the period of the study there was a serious decline in the condition of the trees, with few large trees in the “good” category by 1997. The decline was particularly marked between 1978 and 1981 after a period of well-below average annual rainfall. Using data based on the rate of decline over the period 1978–1997, predictions were made of the fate of the trees in the patch. By 2125 only 46 (11% of the 1981 total) salmon gums were predicted to be alive with only one in the “good” category. Only 16 (17%) York gums were predicted to be alive by 2125, with only one in the “good” category. There was no evidence of any regeneration of woodland trees since 1929 when the patch was isolated by clearing for agriculture, and domestic livestock allowed to graze the patch. This deterioration of the dominant trees in the patch is symptomatic of remnant native vegetation over vast areas of Australias extensively cleared wheat–sheep regions. The future of woodland patches like the one studied is bleak, as is the future of animals dependent on them for food, breeding sites and shelter. Active management, including fencing to exclude domestic livestock and measures to encourage regeneration of native plant communities, is necessary to counter the present regime of benign neglect that characterises most of Australias management of native vegetation in agricultural landscapes.

Variability between Scales: Predictors of Nomadism in Birds of an Australian Mediterranean-climate Ecosystem

Nomadism in animals is a response to resource distributions that are highly variable in time and space. Using the avian fauna of the Mediterranean-climate region of southcentral Australia, we tested a number of variables to determine if they predicted nomadism. These variables were species body mass, the distance in body mass terms to the edge of a body mass aggregation, and diet (for example, seeds, invertebrates, nectar, or plants). We utilized two different classifications of the avifauna that diverged in their definition of nomadic to build two different predictive models. Using both classifications, distance to the edge of a body mass aggregation was found to be a significant predictor of nomadism. There was also evidence that nomads tend to feed on nectar and tend to be large. The significance of the variables body mass and diet (nectar) may reflect the greater energy requirements of large birds and the inherent variability of nectar as a food source. The significance of the variable distance to the edge of a body mass aggregation provides further evidence of inherent variability in resources between domains of scale. The edges of body mass aggregations are hypothesized to be areas of increased resource variability that reflect the transition from one scale of landscape pattern to another.

Nature grows in straight lines—or does she? What are the consequences of the mismatch between human-imposed linear boundaries and ecosystem boundaries? An Australian example

Abstract Sustainability in agricultural landscapes means that the use and management of ecological potential does not reduce its capacity to meet society’s future environmental, social and economic needs. Using this description of sustainability, Australian agricultural systems are far from sustainable at present. Removal of vast areas of native vegetation and the introduction of inappropriate agricultural systems have resulted in extensive loss of native biota, loss of productive agricultural land and decline in rural society. These degrading trends will continue to worsen unless Australian society intervenes on a broad scale. For example, to stop water tables from rising with attendant salination of soil, it has been estimated that over 30 billion perennial trees and shrubs will need to be planted. How does a society generate the will and ability to tackle environmental problems at this scale when its community and institutional boundaries do not reflect ecological reality? This paper discusses these issues and concludes with a 10-point plan to guide development of an approach to sustainable landscapes.

Species survival in fragmented landscapes: where to from here?

We summarise the contributions of empiricists, modellers, and practitioners in this issue of Biodiversity and Conservation, and highlight the most important areas for future research on species survival in fragmented landscapes. Under the theme ‘uncertainty in research and management’, we highlight five areas for future research. First, we know little about the effects of density dependence on the viability of metapopulations, a requirement for fragmented landscapes. Second, successful early attempts suggest that it is worth developing more rigorous calibration methods for population viability analysis with spatially explicit, individual-based models. In particular, the balance between model complexity, ease of calibration, and precision, needs to be addressed. Third, we need to improve methods to discriminate between models, including alternatives to time-series approaches. Fourth, when our ability to reduce model uncertainty is weak, we need to incorporate this uncertainty in population viability analysis. Fifth, population viability analysis and decision analysis can be integrated to make uncertainty an explicit part of the decision process. An important future direction is extending the decision framework to adaptive management. Under the theme ‘tools for quantifying risk and predicting species sensitivity to fragmentation’, we highlight three areas for future research. First, we need to develop tools to support comparative approaches to population viability analysis. Second, population modelling can be used to find rules of thumb to support conservation decisions when very little is known about a species. Rules of thumb need to be extended to the problem of managing for multiple species. Third, species’ traits might be useful for predicting sensitivity but predictions could be further refined by considering the relative importance of population processes at different scales. Under the theme ‘tools for reassembling fragmented landscapes’, we consider the ‘focal species’ approach, and highlight aspects of the approach that require more rigorous testing. Finally, we highlight two important areas for future research not presented in the previous themes or papers in this volume. First, we need to incorporate the deterministic effects of habitat modification into the modelling framework of population viability analysis. Second, an avenue of research that remains largely unexplored is the combination of landscape-scale experiments and population modelling, especially using data from existing fragmentation experiments and from experiments designed to test the effects of defragmenting landscapes.