Bushland management pays dividends
Mosman’s bushland is looking and feeling better, with recent data demonstrating significant improvements to native vegetation cover over the past 10 years. The excellent results can be attributed to long-term planning and a holistic approach to environmental management.
The current Bushland Restoration Contracts 2001–2011 expired on 30 September 2011. These contracts were introduced concurrently with the Community Environmental Contract (CEC) and were innovative in regard to duration, catchment based approach, and performance measurement criteria.
They have been successful with on-ground results exceeding targets, e.g. the 2010–11 MOSPLAN target for areas under contract having greater than 90% native vegetation cover (density) was 45%. The actual figure achieved was 58%. This is a significant increase from Council’s target and highlights the positive contribution the bushland contract work has had on our bushland sites. The ten-year contract has allowed a consistent work methodology and given the contractors a sense of ownership and pride in improving the biodiversity, health and long-term sustainability of these areas.
The result is particularly satisfying considering the difficult task of raising the native vegetation cover in areas where they have been historically modified and each site has a relatively large edge to area ratio. Basically the sites have been highly fragmented and are heavily exposed to external pressures from the urban environment. The work also demonstrates the benefits of creekline, seawall restoration and drainage works under the CEC.
Over the contract period 2001–2011 the bushland area under contract which has greater than 90% native vegetation cover has increased from less than 25% to 58%. The 2001 figure is an estimate as the contracted bushland sites were not mapped for native vegetation cover but for resilience and weed density. Therefore actual figures of area are not available and native vegetation cover for a site has been calculated from the weed density and resilience maps created from an initial flora and fauna survey in 2001.
This information is presented in Table 1. It also shows the percentage classification of native vegetation density for each site in 2006 and again in 2011, and reflects qualitative data for indigenous vegetation cover collected at all sites. This involved each bushland site being assessed by an ecologist and the same methodology of data collection was used in both 2006 and 2011. Each site was extensively surveyed in the field and native vegetation cover broken up into four categories (30%, 30–69%, 70–89% and 90+ %). This data was then mapped and totalled for each site and as a whole. For each site an average cover was determined.
From 2006 to 2011 the contracted bushland sites have an 18% reduction in areas of <30% native vegetation cover, a 17% reduction in 30–69% native vegetation cover, an increase of 12% of 70-89% native vegetation cover, and an increase of 12% of 90+% native vegetation cover.
Table 1: Change of Native Vegetation Cover for Bushland Contracted Sites from 2001–11
|Bushland Site||% Classification of Indigenous Vegetation Cover|
|Quakers Hat South||30-69%||70-89%||70-89%|
|Quakers Hat North||30-69%||30-69%||30-69%|
|Quakers Hat Park||70-89%||90+%||90+%|
|Sirius Park East||30-69%||70-89%||70-89%|
|Sirius Park West||30-69%||30-69%||30-69%|
| *Percentage of Bushland with
*Percentage of bushland with 90+% classification of native vegetation cover is a measurement determined by adding up individual areas of 90+% in each bushland site and totalling these and comparing against overall area managed by the bushland contracts.
For current distribution of native vegetation cover for each bushland site please refer to Maps – Distribution of Native Vegetation Cover for Contracted Bushland Sites.
It is clear that each site has responded well to bushland restoration techniques and management strategies. Sites such as Quakers Hat North, Lawry Plunkett and Sirius Park West, while still in the same overall classification of native vegetation cover of 30–69%, have also had significant improvement in the condition of bushland.
Further, for some sites where low levels of native vegetation cover remain it may have been determined through the sites’ Annual Work Plans to keep particular areas at low classification levels as the area may be providing suitable fauna habitat; was impractical to access safely; or erosion of the ground may occur if removed. Also on some sites resources may not have been available for primary clearance works as it may have been determined to leave and consolidate the better areas of the site as per the Bradley Method of bush regeneration.
Also some sites such as Harnett Park and Wyargine Bushland had minimal improvement in some areas due to factors not necessarily related to contractor works performance. For Harnett Park the dominance of Coral trees on the southern facing section of this site makes it extremely difficult to improve overall vegetation cover classification as these trees shade out native plant regeneration in summer and their leaf drop shades out native plant regeneration in winter and also adds unwanted nutrients to the soil. This section of Harnett Park will remain at a low level classification until resources can be found to address the Coral tree dominance. The presence of non-indigenous and mesic trees over many sites is consistently a hindrance in raising native vegetation cover.
For Wyargine Bushland it was resolved by Council that herbicide spraying could not take place. Therefore with the resources allocated to the site contract improvements to vegetation cover could not be made in all areas. A considerable amount of time was taken up by hand weeding when normal and best practice would involve the spraying of these areas with herbicides. This would have allowed greater coverage and more time at each visit for other bush restoration activities aimed at improving the site rather than limiting the spread of weeds from certain areas of the site. This issue is currently being addressed by dedicated Bushcare volunteers (supervised by Council’s Bushcare Officer) where their increased labour effort in certain areas is allowing the contractors to spend more time in other areas of the site and native plants can get established.
Bushland Restoration Contracts review
Given the need to review the outcome of the existing contract performance and to have any new contract commence at the best time of year, an extension of the existing contract until April 2012 was sought and accepted by Council. It is considered prudent to start the new contracts at a time of year when vegetation and especially weed growth is slowing and mid-autumn is considered a good time to abate this effect. This start date would allow contractors time to become familiar with sites prior to the high vegetation growth period in the following spring.
Maps – Distribution of Native Vegetation Cover for Contracted Bushland Sites
- Indigenous Vegetation Percentage Maps May 2011 - Middle Harbour West (PDF 2MB)
- Indigenous Vegetation Percentage Maps May 2011 - Middle Harbour East (PDF 3MB)
- Indigenous Vegetation Percentage Maps May 2011 - Port Jackson Catchment (PDF 3MB)