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biodiversity “Settlements surrounded and connected by native plants, buzzing with the sounds of birds and frogs and a multitude of tiny living things. Bilbies and bettongs in every primary schoolyard. Council and local research institutions working together toward a sustainable future.” City of Mitcham Community Visioning Forum, December 1998. Biological diversity, or biodiversity, refers to the variety of life-forms: plants, animals and micro-organisms, the genes they contain and the ecosystem of which they form a part. An ecosystem refers to the complex networks formed by the interactions of species in a given area with each other and with their environment. Biodiversity should be considered at three distinct levels: ecosystem diversity species diversity, and genetic diversity. To accurately track biodiversity in the City of Mitcham, indicators of biodiversity should be developed at each of these levels. WHY IS BIODIVERSITY IMPORTANT? The Commonwealth State of Environment Report (1996) points out that biodiversity is important for four reasons: Healthy ecosystems make all life possible; they maintain the quality of the air we breathe, they maintain and regulate the climate, fresh water, soil formation, recycling and disposal of wastes. It is ethically wrong for one species or generation to use the Earth’s resources exclusively for their own use. Many Australians place a high aesthetic and cultural value on native plants and animals. They are essential to our sense of cultural identity, spiritual enrichment and recreation. City of Mitcham State of Environment Report 11 Biodiversity is also of economic importance through the control of pest plants, animals and diseases, the pollination of crops, and the provision of building materials, medicines and tourism. Increased vegetation covering also helps to combat global warming through sequestration of greenhouse gases. The Commonwealth report concludes that: ‘future generations are unlikely to forgive further losses of biodiversity through bad management or lack of commitment, especially now that its precarious state is recognised’. MEASURING BIODIVERSITY PRESSURE PEST PLANTS AND ANIMALS This indicator provides a measure of distribution and abundance of those introduced plant species causing significant problems of posing significant threats. Since colonial days the City of Mitcham has been colonised by a range of introduced plant and animal species which, without natural competitors, parasites and diseases have placed great pressure on the biodiversity of the area. The severity of pest plant infestation can be affected by several factors including: growth patterns, habitat and adaptability to receiving environments, soil types, rainfall, shaded areas and water ways. The olive is one such plant that has adapted readily to the hills environs around Adelaide. 12 City of Mitcham State of Environment Report SEVERITY OF PEST PLANTS INFESTATION : CITY OF MITCHAM 1992 – 1998 GROUP Trees Shrubs Ground covers, grasses COMMON NAME BOTANICAL NAME SEVERITY RATING 0–5 (5 = most severe) 5 4 4 3 3 5 5 2 2 4 2 2 3 4 5 5 5 4 2 3 3 4 Olives Buckthorn Tagasaste Aleppo pine Azzarola Desert ash Montpellier Broom Hedge Broom Scottish Broom Topped lavender Sweet Briar Dog Rose Milkwort Bamboo Pampas Grass Blackberry Boneseed African daisy Hemlock Boxthorn Olea europeaea Rhamnus alaternus Cytisus proliferus Pinus halepensis Crataegus sinaica Fraxinus oxycarpa Genista monspessulana Cytisus racemosus Cytisus scoparius Lavandula stoechas Rosa rubiginosa Rosa canina Polygala myrtifolia Arundo donax Cortaderia selloana Rubus ulmifolius Chryanthemoides monilifera Senecio pterophorous Conium maculatum Lyciium ferocissimum Crassula German Ivy Osteospermum Gazania Common Ivy Field bindweed Tangier pea Nasturtium Periwinkle Horehound Tricolour harlequin flower Bubil watsonia False hair grass Fountain Grass Petty spurge Kikuyu Senecio mikanioides Osteospermum fruticosum Gazania spp Hedera helix Convolvulus arvensis Lathyrus tingitanus Tropaeolum majus Vinca major Marrubium vulgare Sparaxis tricolor 3 4 4 3 3 3 2 4 4 Watsonia bulbillifera Pentaschitis airoides Pennisetum setaceum Euphorbia peplus Pennisetum clandestinum 5 3 3 3 2 Source: Compiled by David Deer, Horticultural Consultant, City of Mitcham Note1: Native vegetation introduced from other States can also be considered weeds in some locations. A list of these plants is currently being compiled. Note2: This table rates pest plants according to the severity of current and potential impact on the biodiversity of the City. City of Mitcham State of Environment Report 13 How Are We Doing? The data shows that weed infestation is a major threat to biodiversity in the City. The effects are seen most clearly adjacent waterways, with almost the total length of watercourses affected to some degree. Much of the original native vegetation in these areas has been lost or replaced by weeds (PCWMB 1998a). Native fauna also faces significant pressure from introduced plants and animals. Cats (domestic and feral), rabbits and foxes are also are an acknowledged concern although specific numerical data is not available. A cat-by law has been proposed by Council (January 1999) and is awaiting Parliamentary approval. A high land consumption rate can also place pressure on natural habitats and threaten biodiversity (Commonwealth, 1998b). Urban density and land use indicators are discussed in the Land Management Chapter of this report. CONDITION NUMBER OF THREATENED SPECIES This indicator is a good measure of species diversity and indicates which groups may need special management. THREATENED SPECIES SIGHTED WITHIN THE CITY OF MITCHAM 1992 -1998 Major Group Vegetation Animals 14 Species Ferns Native Pines Trees/Shrubs Grasses Birds Reptiles, Mammals, Amphibians Butterflies Number of Threatened Species 2 2 41 19 12 insufficient data 1 Note 1: For full lists of these species, their conservation status, and sources of this data, refer to Appendices 5-8. Note 2: The data should be interpreted with care because increases in species at risk can be attributed to increased knowledge of species that were already at risk. City of Mitcham State of Environment Report How Are We Doing? The data shows that the City of Mitcham is in a unique position to aid the protection and enhancement of native flora and fauna species. It is also important to note that species diversity is closely linked to ecosystem diversity. The retention of plant associations or communities is as important (or more important) as protecting specific species. In this area, too, the City of Mitcham can play a vital role in preserving communities of threatened vegetation. The City contains some of the last remaining examples of eucalyptus microcarpa (grey box) woodland in the State. These woodlands have been given a high conservation priority rating by the State Environment Department (Neagle 1992). Although one species of butterfly is threatened, eight species have become extinct within the City limits. The retention of caterpillar foodplant for the threatened butterfly species will ensure its survival in Micham, but more importantly, the planting of foodplants and nectoring plants for the ‘extinct’ species may provide suitable habitat for these species to re-establish. AREA OF NATIVE VEGETATION AS A PERCENTAGE OF TOTAL COUNCIL AREA This indicator is the best available measure for the condition of ecosystem diversity. The best available data shows: Area of City of Mitcham Area of (Overstory) Native Vegetation (1986) Native Vegetation as percentage of total area City of Mitcham State of Environment Report 7468.5ha 1734.83ha 23.23% 15 Native Vegetation Vegetation heritage agreement NPWS reserve City of Mitcham boundary Major Road Minor Road Source: Planning SA Note 1: Although the native vegetation data dates from 1986 it is included as a baseline for future reference. Improved satellite mapping systems will enable more regular assessment of this indicator. Planning SA will complete a similar but more extensive mapping of native vegetation by mid1999. Note 2: Data refers to tree canopy only, it does not reflect the quality of native vegetation, particularly as regards weed infested areas. Nor does it reflect the degree or quality of understory vegetation. How Are We Doing? The available data shows that Mitcham has a relatively high percentage of native vegetation in comparison to most metropolitan Adelaide Councils. Changes in this indicator will reveal the success or otherwise of strategies to enhance native vegetation in Mitcham. 16 City of Mitcham State of Environment Report RIVER HEALTH ‘River health’ is a concept that goes beyond suitability of water for particular uses and integrates a range of ecosystem values and functions. (ANZECC 1998). It is a good measure of ecosystem diversity. A one off testing project of water animals (aquatic macroinvertebrates) and plants (aquatic microphytes) was done by Professor W.D Williams in April 1996. The project was intended as an overall indication of ecological condition. A scale of 0-5 was used to rate the ecological condition. Summary of Biological River Health Sampling Points April 1997 River Name Sturt River Brownhill Creek Sampling Point Ecologocial Status (5 High 0 Low) Stirling (Pole Road) 3 Coromandel Valley (Frank Smith Park) 3 Coromandel Valley (Murrays Hill Road) 4 Bedford Park (Caravan Park) 4 Bedford Park (upstream of Sturt Road) 4 Brownhill creek (upper reaches) 1 Brownhill creek (caravan park) 1 Torrens Park (Mitcham Reserve) 1 Hawthorn (Memorial Gardens) 0 Source: Patawalonga Catchment Water Management Board (1997a) Note 1: Further sampling of macroivertebrates was carried out at five sites during preparation of the BCEAP (1998). Results broadly supported Professor Williams’ work. Note 2 This indicator is strongly linked to the catchment management indicators discussed in the Chapter 3. City of Mitcham State of Environment Report 17 How Are We Doing? As a result of the above sampling, the PCWMB (1997a) reached the following conclusions about the health of the two main watercourses in the City of Mitcham: “…for most of the course of the (upper) Sturt River has a relatively diverse and abundant macroinvertebrate fauna, … not too far removed from pre-European status. There seems little doubt that this reflects the protection offered by the Sturt Gorge Recreation Reserve in the middle reaches and the still relatively undeveloped nature of the upper part of the catchment. “Brownhill Creek [is] in poor condition … virtually insignificant amounts of aquatic life exist.” RESPONSE NUMBER AND SIZE OF PROTECTED AREAS Protected areas are necessary, although alone are not sufficient, to enhance biodiversity at all levels. State or Commonwealth Protected Areas in City of Mitcham, 1998 Area (Hectares) Belair National Park 828.61 Brownhill Creek Recreation Park Shepherds Hill Recreation Park Sturt Gorge Recreation Park Private Land (Heritage Agreements) Saddle Hill Reserve Watiparinga Reserve Blackwood Hill Reserve TOTAL 50.84 77.12 32.40 1.17 15.90 24.10 60.00 1090.14ha Source: Planning SA, City of Mitcham Horticultural Consultant Note 1: Data does not include 200ha State government land at Craigburn farm. It is intended that this land will be incorporated into the Sturt Gorge Recreation Park. Note 2: Data does not include bequests and institutional land at Waite, Flinders University and CSIRO. 18 City of Mitcham State of Environment Report Total Number, Council Reserves, Parks, Gardens, Sport and Recreation Areas, 1999 Ward Boorman Gault Overton Babbage Craigburn Park Number 30 32 22 52 46 24 206 TOTAL TOTAL AREA : COUNCIL MANAGED PUBLIC GREEN SPACE CITY OF MITCHAM 1999 WARD Boorman sport and recreation Boorman parks and gardens Gault sport and recreation Gault parks and gardens Overton sport and recreation Overton parks and gardens Babbage sport and recreation Babbage parks and gardens Craigburn sport and recreation Craigburn parks and gardens Park sport and recreation Park parks and gardens TOTAL (square metres) TOTAL (hectares) AREA (square metres) 88,960 1,093,702 115,350 69,560 78,388 40,102 73,662 756,574 781,369 651,058 65,660 1,072,587 4,886,972 488 Source: Council records, City of Mitcham Horticultural Consultant. Note 1: Improved access to geographic information systems and aerial photography interpretation techniques will enable improved representation of this data in future, and provide a useful tool for planning vegetation corridors to enhance biodiversity. Note 2: This indicator is closely linked to land management indicator ‘council – managed open space’. How are we doing? The data shows that there is great scope for increasing the amount of native vegetation within protected areas. Comparison with more current information being collated by Planning SA and Council will reveal if these opportunities are being pursued effectively. The data also shows significant areas of native vegetation outside protected areas. Changes in this data will show how effectively Council and the community are revegetating non-protected areas with native plants. City of Mitcham State of Environment Report 19 PARTICIPATION IN BIODIVERSITY PROJECTS Bushcare A good medium term measure of the success of strategies to enhance biodiversity will be the level of community awareness and support for biodiversity projects. Although difficult to quantify, growing participation in projects like Bushcare show what can be done in this area. Managed by ‘Trees for Life’ and partly funded by the City of Mitcham, the Bushcare project involves community members in caring for specific sites of native vegetation. The project has grown steadily in recent years. Growth of the Bushcare project in the City of Mitcham Bushcare Sites Bushcarers 94/95 95/96 4 13 10 42 96/97 97/98 17 55 20 61 98/99 21 62 Source: Andrew Allanson, ‘Trees for Life’ Leafy Seadragon-Friendly Catchments Project Participants include the Coromandel Valley Community Association, Coromandel Valley Primary School, Mitcham and Onkaparinga Councils, the Patawalonga Catchment Water Management Board and Greening Australia. Through revegetating the riverine environment of the Sturt River, the project promotes links between land-based activities and the marine environment. Poor water quality outflows to the sea and cause sedimentation of seagrass beds. The project is located along the Sturt River, upstream of the Frank Smith Dam, and involves weed control and revegetation with local indigenous aquatic and terrestrial plant species. The locally threatened species, the Leafy Seadragon, is used to highlight the loss of marine habitat due to pollution of inland waters. Council Biodiversity Projects Council is working on several projects to enhance biodiversity in the City. These include: • 20 an aerial photography mapping project, detailing more accurately the extent of overstory native vegetation in the City. City of Mitcham State of Environment Report • in partnership with the PCWMB and the Natural Heritage Trust, a Biodiversity Action Plan for the Sturt river which will address water quality, hydrology, land use issues, catchment ecology, and native flora and fauna species. • in partnership with the PCWMB and the community, a removal program for introduced vegetation along Brownhill Creek. How Are We Doing? The data suggests there is increasing knowledge within the community about the importance of protecting and enhancing biodiversity. Much remains to be done, however, to actively address the pressures in this area. City of Mitcham State of Environment Report 21 What Can I Do? Plant species native to the area from locally collected seed (obtain a list of plant species from DEHAA, or phone Trees for Life for advice, 8207 8787) Obtain from Council a copy of non-native species to avoid when planning a garden. Become involved with a biodiversity program, like Bushcare. Control weeds on my property, being careful to keep chemicals out of creeks and waterways. Keep my cat within my property boundaries inside the house at night. De-sex my cat. Have my cat wear a bell. Keep my dog on a leash and under supervision. Plant nectoring and caterpillar foodplants (check out foodplants at website, http://www.adelaide.net.au/~reid) Retain species which provide habitat or food for native fauna. If trees must be felled, provide alternative habitat such as nesting boxes for birds. 22 City of Mitcham State of Environment Report What Can Council Do? Develop and implement an Environmental Action Plan to meet the following objectives: 9 Control pest plants and animals that are a threat to our environment. 9 Identify and protect threatened species. 9 Maximise retention of native vegetation. 9 Offset essential clearance with revegetation of indigenous species. 9 Identify, protect and enhance significant habitats and corridors. 9 Develop an appreciation among Council and the community of the importance of native vegetation. City of Mitcham State of Environment Report 23 24 City of Mitcham State of Environment Report