'Invasion debt' after extensive land-use change: An example from eastern Australia

Area of Science:

• Ecology
• Environmental Science
• Conservation Biology

Background:

• Land-use change is a primary driver of global biodiversity loss.
• Invasive species spread is a recognized consequence of land-use change, often difficult to quantify due to limited temporal data.
• Sub-coastal Queensland, Australia, has experienced extensive land development, primarily for agriculture.

Purpose of the Study:

• To investigate changes in land-use, remnant vegetation extent, and invasive plant species spread between 1997 and 2018 in sub-coastal Queensland.
• To assess the effectiveness of conservation policies in protecting remnant vegetation.
• To understand the relationship between historical land-use and current invasive species dynamics.

Main Methods:

• Utilized detailed mapping data for 130,950 km² of sub-coastal Queensland.
• Integrated field survey results to analyze changes over time (1997-2018).
• Quantified land clearing, vegetation reduction, and the spread of specific invasive plant species.

Main Results:

• Significant land clearing (7392 km²) occurred between 1997 and 2017, mainly for grazing and cropping expansion.
• Nationally protected vegetation types were disproportionately affected by land clearing.
• Invasive perennial grasses (Indian couch and buffel grass) significantly increased in cover and presence within remnant vegetation fragments.
• Parthenium weed (Parthenium hysterophorus) also showed a moderate increase.

Conclusions:

• Despite conservation policies, land-use change continues to degrade remnant vegetation in sub-coastal Queensland.
• The spread of invasive grasses suggests an 'invasion debt' from historical land-use intensification.
• Continued monitoring and improved policy implementation are crucial to mitigate threats to remnant ecosystems.