Ten years of invasive plant control mapping 2013-2023

ACT Parks & Conservation Service and Biosecurity & Rural Services EPSDD |City Services TCCS

Weeds or invasive plants?

Weeds are plants growing where they are not wanted. In contrast, invasive species are introduced plants and animals that have a negative impact on environmental and economic assets.

Invasive alien species are animals, plants or other organisms that are introduced by humans, either intentionally or accidentally, into places outside of their natural range, negatively impacting native biodiversity, ecosystem services or human economy and well-being.

So all invasive plants are weeds but not all weeds are invasive plants.

 Invasive plants that degrade large parts of an ecosystem are termed 'Transformers' . Examples of transformers: blackberry, African lovegrass, and serrated tussock.

At a glance

The ACT invasive plants program has focused on innovation in both weed control techniques and mapping. The program has won local and national awards, been featured by Esri as an international case study in best practice mapping, and the mapping data is now being used in a major CSIRO study about adaptive management of invasive plants.

The late Jenny Conolly, and her ACT Parks colleagues, were among the first to use the new citizen science platforms which have become an integral part of the smart mapping system. They were testing iNaturalist in 2011 ( iNaturalist was available in Australia from 2008 ).

Since 2014, Esri ArcGIS Online and iNaturalistAU have been used for smart mapping - recording control work and locations of weeds. Canberra NatureMapr was developed by a local business in around 2014, and it has become one of the main ways Parkcare volunteers report weeds.

Control work areas are recorded in the field using the Esri Field Maps app (formerly Collector app) and synced to ArcGIS Online. Canberra NatureMapr and iNaturalistAU are the main apps used to report and identify invasive plants.

What does the mapping show?

  • Frequent follow-up control is essential for effective invasive plant management. An example is blackberry control in Northern Namadgi National Park.
  • Standard invasive plant control (passive restoration) is more likely to be successful in high quality habitat. Active restoration (e.g. revegetation, soil fertility management) is needed in addition to passive restoration for the management of degraded areas.
  • Loss of control of African lovegrass in urban Canberra and the Murrumbidgee River Corridor is placing significant propagule pressure on nature reserves, Tidbinbilla and Namadgi National Park. This is the number one environmental biosecurity and fire fuel threat for the ACT.
  • Additional specialist invasive weeds Rangers will be needed to protect Nature Reserves in Canberra Nature Park from African lovegrass spread. The benefit of such specialised Rangers has been demonstrated in Namadgi National Park.
  • Research is needed to help with management of St John's wort.
  • Containment of many high risk new and emerging invasive plants. This has been due to additional Biosecurity Rangers focusing on new incursions.
  • Importance of the Citizen Science alert systems for rapid response to new incursions.
  • Citizen Science facilitates early control. Late control is at least 40 times more costly than early control.
  • Ongoing threat from large infestations of transformers along lowland riparian areas, and in low quality habitat. These infestations eventually spread, impacting adjacent high quality habitat.

Field Maps & Citizen Science apps

All public land managers, contractors and volunteers use the same maps on the Esri Field Maps app. These sync to ArcGIS Online, and the data is summarised in dashboards. The mapping system allows for coordination of control work through data sharing.

Citizen Science (iNaturalistAU & CBR NatureMapr) is combined with ArcGIS Online for reporting and identifying invasive plants species. Citizen Science observations are used for facilitating early control, significant species alerts, identification of species and photo-points within a Field Maps app control area polygon.

Example of control work

Spot spraying Oregon grape (native to North America) using metsulfuron methyl in Namadgi National Park

  • Spot spraying with selective herbicide is an important invasive plant control technique often recorded on the Field Maps app.
  • Integrated control combines different control measures, such as spot spraying, slashing and biological control.
  • Removal of invasive plants makes space for native plants to regenerate.

Mapping: Citizen Science + Field Maps

Citizen Science is integrated with ArcGIS Online. Combining Citizen Science and ArcGIS Online - Field Maps delivers an all-purpose environmental weed mapping system.

Invasive plant control dashboards and the Field Maps app

 ACT land managers use dashboards to display progress with invasive plant control . The dashboards use ArcGIS Online maps with Field Maps app and Citizen Science data. The 2023-24 dashboard integrates Citizen Science sightings with Field Maps polygons.

Dashboards allow analysis of control work over time by comparing changes in the area and density of infestations. The following dashboards are for viewing on a desktop.

Dashboards can also be designed for viewing on a mobile phone.

Examples of control work

There are four case studies below showing mapping data and corresponding photo monitoring points. Another two case studies show containment of a new incursion species, and the effect of a La Nina event on control of a widespread species. A final case study shows the consequences of missing follow-up control. The data for the charts are from Field Maps app - ArcGIS Online Treated weeds maps and corresponding dashboard data.

Control of Paterson's curse at Mt Majura Nature Reserve

Paterson's curse is from Europe but readily spreads in disturbed and degraded areas in SE Australia. 'The Fair' site at Mt Majura was a good example of such spread.

Mulching and revegetation were required in addition to standard weed control. Friends of Mt Majura invested considerable time into this restoration project.

Friends of Mt Majura restoration site at Mt Majura Nature Reserve. Top left, Paterson's curse dominated the area in 2012. This was sprayed with selective herbicide, followed by direct seeding of native plants and addition of Eucalyptus mulch, at top right. Planting of local native shrubs and trees commenced along with follow-up spot spraying and further mulching and direct seeding, at bottom left. Bottom right in winter 2021, with native grasses and shrubs well established.

Control of blackberry in Northern Namadgi National Park

Northern Namadgi National Park has tall Eucalypt forests and sub-alpine vegetation. It is high quality habitat. However, gullies, like Moonlight Hollow, are susceptible to blackberry invasion, the berries being spread by birds, such as Currawongs. Blackberry is native to Europe but is invasive in SE Australia.

High quality habitat regenerates readily after control of transformers such as blackberry. So once density was reduced the native plants began to fill the space left by the dead blackberry.

Blackberry control using spot spraying of selective herbicide at Moonlight Hollow in Namadgi National Park. The infestation at top left was discovered in late 2009, starting to smother the tree-ferns. The photos span 10 years from initial control in 2010 at top right, to the most recent photo at the bottom taken in late 2020. A diverse range of native plants have regenerated in the space left by the dead blackberry.

Control of serrated tussock at Jerrabomberra Grasslands Nature Reserve

Serrated tussock is from South America but readily invades native grasslands and pasture in SE Australia. It decreases biodiversity by smothering other grasses and wildflowers. At the Aero Club paddock it was the dominant plant before control work commenced.

Small remaining infestations have a high density because of low native perennial grass cover at those sites. Area occupied (infestation size by density) has clearly declined.

Serrated tussock control using herbicide spot spraying, ecological burning, soil nutrient management, and reduced grazing pressure (ie. integrated control) at Jerrabomberra Grasslands Nature Reserve. The photos span 15 years, commencing with the initial spot spraying of the serrated tussock (top photo) in 2005. Many years of follow-up spot spraying was required to bring the serrated tussock under control, allowing the native grasses to regenerate. Bottom left photo is in late winter 2020, showing native grasses (mainly tall speargrass and red grass) dominating the grassland. And at bottom right in Spring 2020, the native grassland in seed.

Control of nodding thistle in Namadgi National Park

Nodding thistle is from Europe, Asia and northern Africa. It is an invasive plant in the high country of SE Australia. Dense, persistent infestations can establish in disturbed grassland. A high severity fire allowed a large infestation to establish at Long Flat. Herbicide control and direct seeding of native grasses restored the site.

Remaining isolated infestations have a high density due to lack of perennial grass cover in disturbed sites. Area occupied (infestation size by density) has clearly declined after restoration work commenced in 2018-19.

Nodding thistle control in Namadgi National Park using integrated management. Top left photo shows nodding thistle rosettes invading the burnt river tussock native grassland. Top right shows the dense growth of mature nodding thistle plants, suppressing native plant regeneration. Selective herbicide was used during 2018-20 to control the nodding thistle. Other control methods used included: grazing exclusion to allow native grasses to recover, leaky weirs to encourage native colonisers, and direct seeding of the native river tussocks. The photos at the bottom are taken in Spring 2020 (bottom left) and late Autumn 2021 (bottom right), showing successful restoration of the native grassland.

Control of Mexican feather grass in Namadgi National Park

Mexican feather grass is from southern USA and South America. It has the potential to be highly invasive in SE Australia and is prohibited from sale. In the past it was sold under different names to unsuspecting members of the public. Most infestations in the ACT were in urban areas. All have been eradicated due to rapid response and thorough follow-up control.

Mexican feather grass in an ACT garden.

The infestation at Bendora Dam in Namadgi National Park spread from the garden at the Ranger's house. The plants had been mis-labelled by a plant nursery as native spear grass. There was frequent follow-up control which prevented the 'garden escapes' from seeding. This stopped the development of a large seed bank which would have taken much longer to deplete.

Control of new incursion invasive plants has been relatively successful since additional resources were allocated to active surveillance and eradication. The detection power is 0.90, or 90% of high risk new incursions are detected and eradicated before becoming widespread. Mexican feather grass is one of the higher risk new incursions that has been eradicated. The others are: mouse-ear hawkweed, spotted knapweed, and Hudson pear.

Chilean needle grass control and a La Nina event

Chilean needle grass is a major threat to native grasslands and grazing lands in SE Australia. It responds rapidly to increased rainfall.

Chilean needle grass in the early stages of invading a native grassland

Higher rainfall in 2020-22 resulted in Chilean needle grass germination, which corresponds with the increase in the infestation area in 2021-22. It was important to find the newly germinated plants before they set seed.

Missed follow-up control - a reason for poor results

Follow-up control of invasive plants is essential to reduce seed banks and prevent reinfestation. Highly invasive species, such as invasive grasses, quickly take advantage of missed follow-up control. Serrated tussock is from South America and is highly invasive in SE Australia. Its seed can spread large distances on the wind and it germinates readily in disturbed areas.

Fluctuating follow-up control effort (incomplete or missed) leads to fluctuating infestation density, and makes it difficult to reduce the overall infestation size.

Credits & references

Thank you to the dedicated and hardworking staff, contractors and volunteers protecting our unique native flora from invasive plants.

The GIS expertise of current and former employees of ACT Parks, notably Allan Bendall, Alexi Williams, and Josh Thomson, was essential in the early testing of smart mapping.

Thank you to the late Jenny Conolly, and her ACT Parks colleagues, as they were among the first to use citizen science in the ACT with the testing of iNaturalist in 2011 (iNaturalist was available in Australia from 2008). This later became iNaturalistAU hosted by the Atlas of Living Australia.

The citizen science platform Canberra Nature Map (now NatureMapr) started being used as an additional citizen science platform in 2014. Thank you to Dr Michael Mulvaney, Aaron Clausen, and colleagues for developing NatureMapr. It has become one of the main ways volunteers report infestations of weeds in the ACT.

The Australian Citizen Science Association has successfully promoted citizen science and developed partnerships between the community and professional scientists.

Thank you to ACT Parks GIS experts: Gee Fernando, Peter Kreider, Karl Newport, and Jen Smits, for assistance adding citizen science data to ArcGIS Online.

And thank you to Thomas Mesaglio of iNaturalistAU for technical advice regarding integration of citizen science data into other mapping systems.

Andrew Cox and colleagues of the Invasive Species Council have played an important role in raising the awareness of the impact of invasive species on native plants and animals. This has helped with resourcing of invasive species management across the country.

The CSIRO and the Atlas of Living of Australia have provided expert analysis of smart mapping data, and provided a system for biosecurity alerts from citizen science apps. Many thanks.

Dr Stephen Johnson of the NSW Department of Primary Industry, Hillary Cherry of the NSW National Parks and Wildlife Service, Kate Blood of the Victorian Department of Energy, Environment, and Climate Action, and Dr Paul Downey provided valuable information on invasive plant control and weed risk management.

Story map prepared by:

Steve Taylor |  parkranger818@gmail.com  | Retired Ranger and Biosecurity Program Manager

 Harley.Baker@act.gov.au  | Invasive Species Ranger-in-charge

 Megan.Wyllie@act.gov.au  | Acting Manager Invasive Plants and Plant Pests

 Kirsten.Tasker@act.gov.au  | Biosecurity and Rural Services Program Manager

 Jamie.Metcalfe@act.gov.au  | Invasive Species Ranger

 Michael.Tweedie@act.gov.au  | Former Invasive Species Ranger

ACT PCS - ACT Parks and Conservation Service | BRS - Biosecurity & Rural Services

EPSDD - Environment, Planning and Sustainable Development Directorate TCCS - Transport Canberra and City Services

Photos

ACT PCS, BRS, and Friends of Mt Majura

Mapping - Field Maps app - ArcGIS Online

Copyright Esri Australia

Citizen Science is integrated with ArcGIS Online. Combining Citizen Science and ArcGIS Online - Field Maps delivers an all-purpose environmental weed mapping system.

Mulching and revegetation were required in addition to standard weed control. Friends of Mt Majura invested considerable time into this restoration project.

Friends of Mt Majura restoration site at Mt Majura Nature Reserve. Top left, Paterson's curse dominated the area in 2012. This was sprayed with selective herbicide, followed by direct seeding of native plants and addition of Eucalyptus mulch, at top right. Planting of local native shrubs and trees commenced along with follow-up spot spraying and further mulching and direct seeding, at bottom left. Bottom right in winter 2021, with native grasses and shrubs well established.

High quality habitat regenerates readily after control of transformers such as blackberry. So once density was reduced the native plants began to fill the space left by the dead blackberry.

Blackberry control using spot spraying of selective herbicide at Moonlight Hollow in Namadgi National Park. The infestation at top left was discovered in late 2009, starting to smother the tree-ferns. The photos span 10 years from initial control in 2010 at top right, to the most recent photo at the bottom taken in late 2020. A diverse range of native plants have regenerated in the space left by the dead blackberry.

Small remaining infestations have a high density because of low native perennial grass cover at those sites. Area occupied (infestation size by density) has clearly declined.

Serrated tussock control using herbicide spot spraying, ecological burning, soil nutrient management, and reduced grazing pressure (ie. integrated control) at Jerrabomberra Grasslands Nature Reserve. The photos span 15 years, commencing with the initial spot spraying of the serrated tussock (top photo) in 2005. Many years of follow-up spot spraying was required to bring the serrated tussock under control, allowing the native grasses to regenerate. Bottom left photo is in late winter 2020, showing native grasses (mainly tall speargrass and red grass) dominating the grassland. And at bottom right in Spring 2020, the native grassland in seed.

Remaining isolated infestations have a high density due to lack of perennial grass cover in disturbed sites. Area occupied (infestation size by density) has clearly declined after restoration work commenced in 2018-19.

Nodding thistle control in Namadgi National Park using integrated management. Top left photo shows nodding thistle rosettes invading the burnt river tussock native grassland. Top right shows the dense growth of mature nodding thistle plants, suppressing native plant regeneration. Selective herbicide was used during 2018-20 to control the nodding thistle. Other control methods used included: grazing exclusion to allow native grasses to recover, leaky weirs to encourage native colonisers, and direct seeding of the native river tussocks. The photos at the bottom are taken in Spring 2020 (bottom left) and late Autumn 2021 (bottom right), showing successful restoration of the native grassland.

Mexican feather grass in an ACT garden.

The infestation at Bendora Dam in Namadgi National Park spread from the garden at the Ranger's house. The plants had been mis-labelled by a plant nursery as native spear grass. There was frequent follow-up control which prevented the 'garden escapes' from seeding. This stopped the development of a large seed bank which would have taken much longer to deplete.

Chilean needle grass in the early stages of invading a native grassland

Higher rainfall in 2020-22 resulted in Chilean needle grass germination, which corresponds with the increase in the infestation area in 2021-22. It was important to find the newly germinated plants before they set seed.

Fluctuating follow-up control effort (incomplete or missed) leads to fluctuating infestation density, and makes it difficult to reduce the overall infestation size.