Optimal dynamic control of invasions: applying a systematic conservation approach

Area of Science:

• Ecology
• Environmental Management
• Conservation Planning

Background:

• Invasive plant species pose significant social, economic, and environmental risks.
• Current weed management funding often overlooks the variable impacts of invasive species.
• Spatial prioritization methods need enhancement to account for diverse threatened values.

Purpose of the Study:

• To extend spatial prioritization methods for optimal budget allocation in invasive species management.
• To integrate eradication and control measures to minimize invasion costs and likelihood.
• To develop a multi-year dynamic prioritization approach considering multiple threatened values.

Main Methods:

• Applied a dynamic prioritization framework to the Daly catchment, Northern Territory, focusing on gamba grass (Andropogon gayanus).
• Interfaced Marxan (conservation planning tool) with a gamba grass biophysical model.
• Compared "maximize gain" (MaxGain) and "minimize loss" (MinLoss) optimization under constrained and unlimited budget scenarios over 10 years.

Main Results:

• The MinLoss approach is superior when invasive threats are more spatially variable than conservation values.
• MinLoss reduced future infestations by ~8% (constrained budget) and ~12% (unlimited budget) compared to MaxGain.
• Under constrained budgets, control efforts were more efficient than eradication for gamba grass due to its extensive invasion and spread rate.

Conclusions:

• A MinLoss strategy significantly reduces invasive species spread, outperforming MaxGain.
• For constrained budgets and rapidly spreading invasives like gamba grass, prioritizing control is more effective.
• With unlimited budgets, eradication efforts are more efficient for maximizing spread reduction.