Supporting the spatial management of invasive alien plants through assessment of landscape dynamics and connectivity

Invasive alien species are responsible for several negative impacts worldwide. Managing biological invasions is often difficult and the success rate is quite low, but with good planning it is possible to achieve good results. Besides employing the correct methods and techniques, an overall strategy based on landscape dynamics and expected spatial patterns can be fundamental to achieve success. The decision of where to act can be embedded in a general strategy based on several criteria/goals such as control of large populations, connectivity disruption, and so on. This work focused on Acacia dealbata in a Natura 2000 site in Portugal, how the current amount and distribution can affect the spread pattern, and different possible strategies to approach the management. Based on the species dispersal traits, we argue that not only the area but also the perimeter (therefore, the shape) and location of the patches should be considered when fighting the invasion. Three scenarios were designed and compared using the perimeter-area ratio, a landscape dynamics analysis, and a connectivity index. Results show that removing the patches with higher perimeter-area ratio (mostly small satellite patches) would be more impactful than removing the larger patch or removing random intermediary perimeter-area patches first. After this approach based on landscape dynamics, the employment of a connectivity assessment provided an ordered list of patches to remove sequentially. Overall, this approach can be valuable in the early steps of the planning process, supporting better decisions regarding the available resources and contributing to maximize the effectiveness of the action.