Wildlife Movement and Habitat Needs in Manningham by Dr Graeme S. Lorimer, Scott Baker and David Lockwood Manningham City Council 28 June, 2009 Contents EXECUTIVE SUMMARY 1 1. INTRODUCTION 4 2. PROJECT OUTLINE 7 3. FIELDWORK 7 4. ANALYSIS OF FIELDWORK DATA 10 4.1 Measuring the Consistency of Travel Directions 10 4.2 The Importance of Streams 12 4.2.1 Implications for Council 15 4.3 Relative Importance of Creeks and Habitat Quality 15 4.4 Corridor Bottlenecks 16 4.4.1 Implications for Council 19 5. WILDLIFE MOVEMENT THROUGH TREED RESIDENTIAL AREAS 19 5.1.1 Implications for Council 20 6. THE EFFECTIVENESS OF LINEAR REVEGETATION 21 7. STRATEGIC IMPROVEMENT OF CORRIDORS 21 8. FURTHER WORK 22 9. CONCLUSION 22 REFERENCES 23 APPENDIX – SUMMARY OF FAUNA OBSERVATIONS 25 Executive Summary Recommendation A75 of Manningham City Council’s Green Wedge Strategy was to conduct a study into the location and effectiveness of existing habitat corridors and the opportunities for improving mobility of wildlife across the Manningham landscape. We conducted this study in 2006-8 and expanded it to include an investigation of the mobility of fauna in areas other than corridors. This document reports the outcomes of the project and its relevance to Council. A literature survey found that most quantitative demonstrations of the usage of corridors by wildlife anywhere in the world have involved costly and demanding methods beyond Council’s resources, such as genetic analyses and radio tracking. New methods of fieldwork were therefore developed for our project, taking advantage of what has been learned by previous studies of wildlife movements. An extensive program of fieldwork was conducted during 2006-7. The main findings from a literature survey and the fieldwork are that: Wildlife Movement and Habitat Needs in Manningham Page 2 • Habitat fragmentation is a major threat to the survival of indigenous fauna and flora in Manningham. • Manningham’s streams, gullies and valleys are functioning as effective corridors for a range of native birds, including many of the more significant species. This is true even along Brushy Creek and Ruffey Creek, with their sparse and highly fragmented scatterings of native vegetation. Platypus and fish also move along some of the streams. Many bird species prefer to move along valley floors even when there is superficially superior habitat on the adjacent slopes. • A bottleneck on the Mullum Mullum Ck corridor was shown to cause many birds to converge into the neck rather than traverse an untreed expanse. Widening such bottlenecks by revegetation is expected to be beneficial. • Because of the fragmented patchwork of native vegetation in Manningham, a substantial proportion of wildlife movements occur across residential areas with only scattered trees. These movements, and hence the landscape of these residential areas, are important to the maintenance of wildlife in Manningham. Conversely, the movements are important to residents who enjoy the presence of native birds and mammals such as koalas and kangaroos in their neighbourhood. • Along corridors and within treed residential areas, maintenance of native tree cover (and particularly the locally indigenous species) is the most important requirement for facilitating wildlife movements. These movements are important for the survival of both the wildlife and many indigenous plants that rely on wildlife for pollination, seed dispersal or pest control. • Small insect-eating birds do not persist in the absence of a shrub layer that provides them with cover from predators. The species of shrubs are also important. Exotic shrubs and certain Australian native shrubs with prolific nectar production can exacerbate an ecological imbalance between bird species, leading to displacement of small insect-eating birds by aggressive wattlebirds or miners. Loss of small insect-eating birds is associated with outbreaks of insect pests and consequent tree dieback, a major problem in Manningham. • The main ways in which Manningham City Council can support the movement of wildlife are: o Conducting revegetation and habitat restoration to broaden and connect stream corridor vegetation (particularly on the key wildlife corridors listed in Section 7). However, narrow linear plantings are not recommended; o Fostering the same sort of revegetation by private landowners and Melbourne Water; o Using the permit approval process and the Environmental Significance Overlay in the Manningham Planning Scheme to limit habitat fragmentation by land development and vegetation removal, with particular emphasis on stream corridors and gullies; o Using the Manningham Planning Scheme to protect indigenous plants in treed residential areas of Manningham (as well as, to a lesser extent, protecting non-invasive trees from other parts of Australia); o Managing its own bushland reserves in ways that minimise fragmentation, e.g. when choosing alignments for firebreaks or deciding priority areas for habitat restoration; o Favouring locally indigenous plant species in landscaping projects, when such species meet other landscaping requirements; Version 1.0, 28 June 2009 Wildlife Movement and Habitat Needs in Manningham Page 3 o Encouraging gardeners to provide habitat plants for wildlife, perhaps using the model of the ‘Gardens for Wildlife’ program that is run by Knox City Council and the Knox Environment Society. Version 1.0, 28 June 2009 Wildlife Movement and Habitat Needs in Manningham Page 4 1. Introduction Nature and the natural environment are unsurpassed among the things that residents value about living in Manningham, according to a 2005 focus group survey*. People appreciate Manningham’s greenery – particularly its native vegetation – complete with the birds and other wildlife that comes with it. Council therefore has a responsibility of stewardship of nature, in addition to its statutory responsibilities (e.g. under the Victoria Planning Provisions and the Catchment and Land Protection Act 1994). The most important nature conservation issues on which Council has a direct influence can be characterised as follows: • Loss of habitat: Council monitoring shows that the extent of native vegetation is steadily declining, particularly as a result of land development that is controlled by Council under the Manningham Planning Scheme; • Deterioration of ecological condition of habitat: The ecological condition of habitat is showing a tendency to decline due to factors such as drought, weeds, eucalypt dieback and grazing. However, this tendency is being reversed in some areas by bushland management work and curtailment of damaging practices; • Decline of species: Many species of indigenous flora and fauna are at great risk of becoming locally extinct from the municipality. As species disappear from an area, the ecosystem becomes less biodiverse and the system can lose resilience against pressures such as drought and climate change, leading to a chain reaction of further local extinctions. Council’s Economic and Environmental Planning unit is addressing the first two of these points through several programs, including through Planning Scheme Amendment C54 (‘Sites of Biological Significance’), the Biodiversity Incentives Program and the Bushland Management Action Plan. Another program in progress is identifying which species are at risk of local extinction, to what degree and for what reasons. Council’s bushland management team are active in on-ground work to improve the ecological condition of habitat on Council land. The main reason why Manningham is progressively losing indigenous fauna species is that the areas of suitable habitat for the affected species are progressively fragmented into smaller and more isolated patches until they are too small and distant to support the species. Small, isolated populations of a fauna species: • Can be easily wiped out by chance events such as fire or removal of a critical nesting hollow; • May not be able to move between seasonal feeding grounds or breeding grounds; • Are prone to breeding problems such as inbreeding, difficulty finding suitable mates, inadequate food resources for dependent young and poor opportunities for dispersal of young from their parental territories; • Are less likely to be replaced by immigration when a population dies out. The quality of the habitat in small fragments is also compromised by ‘edge effects’, in which external pressures such as weed invasion and cat predation penetrate into the whole area, unlike larger areas that often contain a core of better habitat. * ‘Community Values: A Market Research Report into the Values of Manningham’s Residents’. Marketing Unit, Manningham City Council. Version 1.0, 28 June 2009 Wildlife Movement and Habitat Needs in Manningham Page 5 Indigenous flora species are subject to the same sorts of effects of fragmentation and isolation as fauna. As the habitat for a plant species becomes more fragmented, the fragments eventually become so far apart that pollen and seeds are no longer dispersed between them. Breeding, regeneration and re-colonisation can then fail. The problem is compounded because fragmentation causes not only physical separation of plant populations but also a decline in fauna (particularly birds and insects) that perform pollination and dispersal. Fragmentation of habitat therefore causes loss of flora species, loss of fauna species and deterioration of the ecological condition of habitat. It is recognised globally as one of the main causes of loss of biodiversity. This problem is particularly acute