OPTIMISING THE LONG TERM MANAGEMENT OF INVASIVE SPECIES AFFECTING BIODIVERSITY AND THE RURAL ECONOMY USING ADAPTIVE MANAGEMENT

"A large number of highly damaging invasive non-native species (INNS) have become established in South America. They affect native species, ecosystems and livelihoods. Many INNS are now so widespread that eradication is not an option. Their spread must be contained and their density reduced, in the long-term, in those areas where taking no action is not acceptable. This must be done as cost effectively as possible, and consider:

By how much should INNS density be reduced? This depends on the resources available for management and on the relationship between the abundance of the focal INNS and the harm it causes to people and biodiversity. Considering what harm would be caused in the future if no action was taken now is also important.

How should the desired reduction be achieved? Different individuals in a population contribute differently to spread. Thus, targeting the right age classes or acting in different seasons should be informed by the biology of the species (e.g. large pines produce more seeds than small ones).

Where should the species be reduced? The areas invaded by INNS are often vast and spatial prioritisation is necessary. INNS are not equally damaging in all areas. Some ecosystems and human activities can withstand low density INNS presence, while others are so vulnerable they cannot tolerate even low INNS density. An example is the critically endangered hooded grebe in Austral Patagonia, driven to near extinction by the introduced American mink. The cost of managing INNS also varies spatially, especially in South America, where some areas are very difficult to access and the workforce is sparse. A further important consideration is that INNS are mobile. They have been able to spread when they first invaded, and can re-invade areas from which they have been removed through dispersal. This is both a challenge and an opportunity if management can exploit known patterns of spread. Ecologists have been studying dispersal dynamics in detail for decades, but have rarely used this knowledge to design effective management interventions. For instance, it may be possible to deplete a mobile INNS by intensively removing it from a small, highly attractive area, hence cost-effectively vacuuming a much larger area, or the spread of a plant INNS may be contained by making the establishment of seeds unlikely through spatially targeted land management.

We will design and introduce to stakeholders a user-friendly decision tool that we expect will become widely used in Latin America. To make sure our approach is relevant for different contexts in Latin America, we will work with example species that have large impacts, and for which data already exist (invasive pines, privet, and mink). We will also model plausible scenarios for data-poor pine species, exotic grasses and carnivorous wasps, which impact local communities in Brazil, Argentina and Chile. We will find the most effective strategic management using sophisticated computer simulations considering species ecology, dispersal and intervention costs in a spatial context. We will identify where new data would most effectively reduce uncertainty on the best course of action. The problem we tackle is complex, and we will embed it in a process of co-operative adaptive management, so that managers continually improve their effectiveness by confronting different models to data. We will also use our project as a way to build research capacity in Latin America, by training early career researchers and PhD students by means of research visits, continuous collaboration and workshops.

Our project will have a tangible positive and immediate impact on people and biodiversity in Latin America by delivering a step-change in the management of problematic INNS."