Protecting the ACT from invasive weeds: highlights from 2009 to 2014
Weeds are plants growing where they are not wanted that can have major economic, environmental and social impacts. There are two main types of weeds including weeds of disturbed areas and invasive weeds (see Box 1).
Invasive weeds reduce primary industries productivity and interfere with the ecological and other functions of waterways. They damage nature conservation assets and values, impact on biodiversity by competing with native plants and degrading habitat, and are a significant threat to many of the ACT’s threatened species and ecological communities.
The costs of preventing and controlling invasive weeds and the lost asset value can be significant for land managers, including farmers and government. The ACT Government therefore conducts annual invasive weed control operations (Figure 1) and supports complementary control efforts by rural landholders and community groups.
This work is guided by the ACT Weeds Strategy 2009–2019 (the strategy), which aims to reduce the impact of weeds on the environment, the economy, human health and amenity. The strategy recognises that control of higher-risk invasive weeds is most effective when included in sustainable natural resource and environmental management using a whole of community, industry and government approach.
Highlights of the first five years of the strategy, from 2009 to 2014, include:
- improved risk assessment, delivery and reporting of government weed control operations
- enhanced capacity to detect, contain and eradicate new weed incursions
- increased control of Weeds of National Significance (WoNS) and several highly invasive grasses
- adoption of innovative approaches to weed control and
- greater collaboration between local and regional government, landholder and community groups
Weeds of disturbed areas are weeds that take advantage of disturbed conditions to spread. Disturbed areas include gardens, lawns, footpaths, nature strips on roadways, playgrounds and some waterways. Weeds of disturbed areas are often annual grasses and herbs that take on an ‘untidy’ look and these are what many people think of as weeds.
Invasive weeds are introduced plants that spread aggressively and cause damage to the environment, the economy and human or animal health. Impacts include smothering native vegetation, reducing farm income, preventing use of recreational areas, triggering allergic reactions and poisoning grazing animals. Most invasive weeds are introduced plants from overseas (e.g. Blackberry from Europe, Serrated Tussock from South America). Some are native plants that have been introduced to an area from outside of their natural range (e.g. Cootamundra Wattle). Invasive weeds are sometimes called invasive plants.
Invasive weeds that occur in native vegetation are also called environmental weeds. Similarly, invasive weeds in agricultural areas are also called agricultural weeds. Invasive weeds, as opposed to weeds of disturbed areas, are the focus of the annual Invasive Weeds Operations Plan (iWOP; see ‘A new weed risk management approach’ below), because they have significant impacts on the environment, agriculture, people and animals.
The ACT Weeds Strategy 2009–19 established five best practice principles that are consistent with the Australian Weeds Strategy:
- 1. Weed management is essential for the sustainable management of natural resources and the environment and for social well-being, and requires an integrated, community-wide approach.
- 2. Prevention and early intervention are the most cost-effective approaches that can be deployed against weeds.
- 3. Successful weed management requires a coordinated approach involving all levels of government in partnership with industry, landholders and community.
- 4. All land managers have a duty of care to manage weeds on their land.
- 5. Community interests shall be protected from weeds by appropriate legislation.
Through the strategy, the ACT Government has improved its capacity to target the highest priority species and assets (such as nature parks) and obtain a greater return on weed control investment.
This has been largely achieved by adapting the NSW Weed Risk Management System for ACT data (Figure 2). This system assigns priority to weeds based on their risk and feasibility of control, and provides guidance on the most appropriate approach to manage the weeds.
Weed risk assessments help the ACT Government categorise declared pest plants in the ACT and prepare an annual Invasive Weeds Operations Plan (iWOP, Figure 3). The annual iWOP summarises expenditure and documents which species will be targeted for control at specific locations within the ACT’s parks and reserves, urban areas and rural roadsides. For 2014–15, nearly 25% of operations will be joint control projects with neighbouring rural landholders.
Each year, areas where invasive weed control operations were completed are mapped and included in the ACT Parks and Conservation Weeds Atlas. This ensures invasive weed control locations are permanently recorded and helps with follow-up control to protect the ACT Government’s initial investment at the site. The map below (Figure 4) is an example from the ACT Parks and Conservation Weeds Atlas. The map shows areas where weed control was undertaken for a range of species in selected Canberra Nature Park reserves and surrounding suburbs.
The most cost effective way to control invasive weeds is to prevent them entering, becoming established and spreading across the ACT. Since 2009, the ACT Government has eradicated incursions of Mexican Feathergrass, African Fountain Grass and Artichoke Thistle. Seven other weed incursions have been contained including Madagascan Fireweed, a high risk Weed of National Significance. Recent responses to Madagascan Fireweed incursions have demonstrated the effectiveness of the ACT’s biosecurity emergency response procedures.
A potential threat analysis has identified weed incursion pathways and provided risk assessments for 20 high priority weeds occurring in the ACT and in neighbouring NSW.
This analysis has been used for the ACT adaptation of the NSW Weed Risk Management System, which is an important part of the annual iWOP (Figures 2 and 3).
The new ACT and Southern Tablelands Weed Spotter website and associated iPhone and Android mobile applications enables community members to record the location of new weed incursions and established weed populations, and record weed control efforts in the CSIRO Atlas of Living Australia.
The information is used by the government to identify incursions early and triggers ongoing control efforts through automatic alerts to government for selected high risk species.
ACT Parks and Conservation staff and contractors are also using the off-line Memory-Map Smartphone applications for mapping weed control areas and uploading this data to the ACT Parks and Conservation Weeds Atlas. A presentation of this work was made at the 19th Australasian Weeds Conference.
The Territory and Municipal Services Directorate has introduced some innovative methods for reaching weeds in relatively inaccessible places. These include:
- abseiling down the Molonglo Gorge to spot spray the highly invasive Prickly Pear (Figure 5)
- use of an eight wheel drive amphibious vehicle, called Argo 800, equipped with a 200 litre tank of herbicide to tackle Blackberry and Tree of Heaven in the rough terrain along the Murrumbidgee River and
- trialling an unmanned remote controlled helicopter equipped with tanks of herbicide to control Blackberry along the Murrumbidgee River.
Weeds of National Significance (WoNS) are high priority species for control based on their invasiveness, adverse environmental, economic and social impacts, and potential for spread across multiple states. From 2009 to 2014, the ACT Government has reduced the threat posed by WoNS through:
- targeting African Boxthorn, Blackberry, Broom, Gorse, Chilean Needle Grass, Madagascan Fireweed, Serrated Tussock and Willows in annual control operations
- declaring 32 WoNS as ‘Prohibited’ pest plants under the Pest Plants and Animals Act 2005 to meet a national agreement to prevent their sale and supply
- completing risk assessments for 13 WoNS species
- developing a Madagascan Fireweed Pest Plant Management Plan (a notifiable instrument under the Pest Plants and Animals Act 2005) that sets out the requirements for control in the ACT and allows for enforcement in the event of non-compliance
- drafting a Serrated Tussock Pest Plant Management Plan
- releasing Scotch Broom Gall Mite for the biological control of Broom species and
- delivering a Caring for our Country-funded, $300,000 devolved grants program targeting control of WoNS by rural landholders and community groups (control activities were undertaken on over 33,000 hectares in the ACT).
African Love Grass is an introduced, low-quality grass that is highly competitive, particularly in infertile soils (Figure 6). It excludes other pasture species and significantly reduces stock carrying capacity.
An ACT Environment Grant helped an ACT rural landholder control African Love Grass using a combination of herbicide application and improved soil fertility to suppress widespread infestations, thereby increasing production of native and introduced pasture species including Weeping Grass and clovers.
This landholder’s work adds to a suite of control methods being adopted by ACT rural landholders (e.g. pasture establishment and vigilant control). These control methods are being promoted through field days and activities undertaken through the ACT Regional Landcare Facilitator program and the work of catchment groups.
An ACT Weeds Forum in 2012 brought together 67 ACT and regional government and non-government stakeholders to explore fresh approaches to reducing the prevalence and spread of existing weeds, and the incursion of new species in a changing climate. The forum generated a suite of recommendations for improving weed management in the ACT, including the development of the ACT and Southern Tablelands Weed Spotter website.
This highly successful forum will become a triennial event, with future forums scheduled for 2015 and 2018.
Over the next five years the ACT Government will aim to address the following strategic priorities, including:
- improved monitoring and evaluation of invasive weed control operations to continually improve their effectiveness and return on investment
- coordinated control of Serrated Tussock threatening Namadgi National Park
- better surveillance for high-risk invasive weeds such as Orange and Mouse-ear Hawkweed through seeking assistance from key stakeholder groups
- developing species-specific response plans to improve rapid response times and eradication success for new weed incursions
- undertaking a review of the plant species recommended for use as street trees and in urban landscape plantings
- improved compliance with vehicle hygiene and mowing protocols to reduce the spread of invasive grasses such as African Love Grass
- maintaining and improving support for community groups undertaking weed control efforts
- reviewing the Pest Plants and Animals Act 2005 so that responsibilities for controlling weeds are clearer.