Ecosystem-wide management of invasive species in the face of severe uncertainty

Abstract

The economic and ecological problems caused by biological invasions underline the importance of invasive species management. Evidence showed that invasive species management aiming to mitigate and reverse negative invasion impacts may lead to unexpected side effects to other ecosystem components, which call for integrating management into broader ecosystem goals rather than manipulating single invasive species in isolation. Decision-making is limited by a severe lack of knowledge yet confronted with urgent needs of conservation management. In this thesis, I focus on developing practical approaches to assist decision-making of invasive species managements in the face of limited information.It can be challenging to resolve the conflicts between invasive species management and other conservation goals. In Chapter 2, I propose to incorporate potential management impacts into a formal decision analysis from a cost-benefit perspective. I conduct a systematic literature review of studies that reported perverse outcomes of invasive plant management, to provide insights for risk identification for future control activities. My results show that there are only 26 publications that identified negative outcomes from plant management. It is possible that such perverse outcomes are merely uncommon, yet we identify that research and publishing biases exist and suggest that the negative impacts of management may have been overlooked. Next, I discuss existing and potential approaches that can be used to identify management risks and reconcile management conflicts, and suggest ways to improve current approaches and facilitate better decision analyses for future management. In the following chapters, I illustrate a number of approaches to assist invasive species management decision-making and illustrate these approaches using two real world management problems.Chapter 3 and Chapter 4 use network approaches to inform decision-making on the management of introduced cats (Felis catus) and rats (Rattus rattus) on Christmas Island. In chapter 3, I conduct a qualitative assessment based on available information to evaluate a number of potential management strategies, which vary in their intensity of both rat and cat control and also vary in cost of implementation. These actions were derived in consultation with on-ground managers from Christmas Island. The assessment suggests that given sufficient resources the optimal strategy is island wide cat eradication with rat control efforts. This suggestion is also supported by the network analysis. Island-wide cat eradication only may lead to secondary impacts through meso-predator release of rats, yet when the resource is limited this strategy still yields more benefits than other management actions such as island-wide cat control, or cat and rat control that are restricted in specific regions.ii In Chapter 4, I developed a novel approach by combining a qualitative modelling approach with Boolean analysis to examine the effects of different management strategies of cats and rats on Ch...

Invasive alien species as simultaneous benefits and burdens: trends, stakeholder perceptions and management

“…IAS with potential or realized benefits are referred to with different names depending on their perceived impact or assessed risk, prior knowledge on the species and the type of conflict they create (Gozlan et al 2013). These species have been referred to as "mixed-blessing" invaders, "multiple-use" resources, "conflict species", species with "ambivalent human preferences", and species that have a "dual-role" or that are both a "value and a nuisance" (Zivin et al 2000;Vigliano and Alonso 2007;Courtois et al 2012;Han 2016;Hui and Richardson 2017;van Wilgen and Wilson 2018;Kourantidou and Kaiser 2019a;Skonhoft and Kourantidou 2021). These terms imply that their impact, either economic, ecological or other (for example cultural), may be seen through both a positive and a negative lens.…”