Abstract
Expanding and creating protected area networks has become a central pillar of global conservation planning. In the management and design of protected area networks, we must consider not only the positive aspects of landscape connectivity but also how that connectivity may facilitate the spread of invasive species, a challenge that has become known as the connectivity conundrum. Here, we review key considerations for landscape connectivity planning for protected area networks, focusing on interactions between network connectivity and the management of invasive species. We propose an integrative adaptive management framework for protected area network planning with five main elements, including monitoring, budgeting considerations, risk assessment, inter-organizational coordination, and local engagement. Protected area planners can address the dynamic aspects of the connectivity conundrum through collaborative and integrative adaptive management planning.
Introduction
Spatial planning for terrestrial protected areas (hereafter PAs) has been of central importance to the discipline of conservation biology for decades (Noss and Harris 1986) and is increasingly important for guiding conservation decisions at global, regional, and national scales. Protected area planners are faced with the challenge of mitigating human environmental impacts, which continue to cause a steady decline in biodiversity and ecological integrity in and around PAs across the planet (Beyer et al. 2019). Addressing these impacts includes planning for PA ecological connectivity, which is now seen as vital for addressing global environmental change (Liang et al. 2018; Stewart et al. 2019). Connectivity amongst PAs facilitates critical ecological processes such as dispersal, seasonal migrations, and species range shifts resulting from climate change, and in doing so, it can prevent deleterious effects, such as inbreeding and local extinctions, thereby helping to maintain ecosystem integrity (Saura et al. 2019). However, ecological connectivity can also have negative effects such as facilitating the spread of disturbances and invasive species. For example, well-connected PAs can act as corridors for the movement of exotic invasive species, such as the emerald ash borer (Agrilus planipennis Fairmaire) or the European fire ant (Myrmica rubra L.) (Resasco et al. 2014; Cuddington et al. 2018). Outbreaks of native species such as mountain pine beetles (Dendroctonous ponderosae Hopkins; Maguire et al. 2015) and spruce budworms (Choristoneura occidentalis Freeman; Drever et al. 2018) can also be facilitated by large contiguous areas of mature coniferous forest. Moreover, the connectivity of anthropogenic disturbances (e.g., road and trail networks, energy infrastructure corridors, and agricultural landscapes) can also facilitate the movement of non-desirable species within and between PAs (Schulze et al. 2018). This can alter predator-prey interactions and facilitate disturbance-mediated species invasions into PAs (Vardarman et al. 2018).
