TY - JOUR
T1 - The cost of not acting
T2 - Delaying invasive grass management increases costs and threatens assets in a national park, northern Australia
AU - Rossiter-Rachor, Natalie A.
AU - Adams, Vanessa M.
AU - Canham, Caroline A.
AU - Dixon, Dan J.
AU - Cameron, Thorsteinn N.
AU - Setterfield, Samantha A.
PY - 2023/5/1
Y1 - 2023/5/1
N2 - Globally, invasive grasses are a major threat to protected areas (PAs) due to their ability to alter community structure and function, reduce biodiversity, and alter fire regimes. However, there is often a mismatch between the threat posed by invasive grasses and the management response. We document a case study of the spread and management of the ecosystem-transforming invasive grass, Andropogon gayanus Kunth. (gamba grass), in Litchfield National Park; an iconic PA in northern Australia that contains significant natural, cultural and social values. We undertook helicopter-based surveys of A. gayanus across 143,931 ha of Litchfield National Park in 2014 and 2021–2022. We used these data to parametrise a spatially-explicit spread model, interfaced with a management simulation model to predict 10-year patterns of spread, and associated management costs, under three scenarios. Our survey showed that between 2014 and 2021–22 A. gayanus spread by 9463 ha, and 47%. The gross A. gayanus infestation covered 29,713 ha of the total survey area, making it the largest national park infestation in Australia. A. gayanus had not been locally eradicated within the Park's small existing ‘gamba grass eradication zone’, and instead increased by 206 ha over the 7-year timeframe. Our modelled scenarios predict that without active management A. gayanus will continue spreading, covering 42,388 ha of Litchfield within a decade. Alternative scenarios predict that: (i) eradicating A. gayanus in the small existing eradication zone would likely protect 18% of visitor sites, and cost ∼AU$825,000 over 5 years – more than double the original predicted cost in 2014; or (ii) eradicating A. gayanus in a much larger eradication zone would likely protect 86% of visitor sites and several species of conservation significance, and cost ∼AU$6.6 million over 5 years. Totally eradicating A. gayanus from the Park is no longer viable due to substantial spread since 2014. Our study demonstrates the value of systematic landscape-scale surveys and costed management scenarios to enable assessment and prioritisation of weed management. It also demonstrates the increased environmental and financial costs of delaying invasive grass management, and the serious threat A. gayanus poses to PAs across northern Australia.
AB - Globally, invasive grasses are a major threat to protected areas (PAs) due to their ability to alter community structure and function, reduce biodiversity, and alter fire regimes. However, there is often a mismatch between the threat posed by invasive grasses and the management response. We document a case study of the spread and management of the ecosystem-transforming invasive grass, Andropogon gayanus Kunth. (gamba grass), in Litchfield National Park; an iconic PA in northern Australia that contains significant natural, cultural and social values. We undertook helicopter-based surveys of A. gayanus across 143,931 ha of Litchfield National Park in 2014 and 2021–2022. We used these data to parametrise a spatially-explicit spread model, interfaced with a management simulation model to predict 10-year patterns of spread, and associated management costs, under three scenarios. Our survey showed that between 2014 and 2021–22 A. gayanus spread by 9463 ha, and 47%. The gross A. gayanus infestation covered 29,713 ha of the total survey area, making it the largest national park infestation in Australia. A. gayanus had not been locally eradicated within the Park's small existing ‘gamba grass eradication zone’, and instead increased by 206 ha over the 7-year timeframe. Our modelled scenarios predict that without active management A. gayanus will continue spreading, covering 42,388 ha of Litchfield within a decade. Alternative scenarios predict that: (i) eradicating A. gayanus in the small existing eradication zone would likely protect 18% of visitor sites, and cost ∼AU$825,000 over 5 years – more than double the original predicted cost in 2014; or (ii) eradicating A. gayanus in a much larger eradication zone would likely protect 86% of visitor sites and several species of conservation significance, and cost ∼AU$6.6 million over 5 years. Totally eradicating A. gayanus from the Park is no longer viable due to substantial spread since 2014. Our study demonstrates the value of systematic landscape-scale surveys and costed management scenarios to enable assessment and prioritisation of weed management. It also demonstrates the increased environmental and financial costs of delaying invasive grass management, and the serious threat A. gayanus poses to PAs across northern Australia.
KW - Andropogon gayanus
KW - Costs of local eradication
KW - Distribution mapping
KW - Gamba grass
KW - Invasive alien plants
KW - Protected areas
UR - http://www.scopus.com/inward/record.url?scp=85147714399&partnerID=8YFLogxK
U2 - 10.1016/j.jenvman.2022.116785
DO - 10.1016/j.jenvman.2022.116785
M3 - Article
C2 - 36758396
AN - SCOPUS:85147714399
SN - 0301-4797
VL - 333
JO - Journal of Environmental Management
JF - Journal of Environmental Management
M1 - 116785
ER -