Drivers of environmental change, such as climate change and species invasions, can alter the distributions of culturally important plant species. Furthermore, synergistic interactions among drivers can lead to unexpected and non-linear changes. Species distribution models (SDMs) are valuable tools for predicting future potential distributions of plant species, but they typically omit the effects of species interactions and rarely incorporate social interests. Tongariro National Park (New Zealand) is a natural and cultural World Heritage Site that is subject to a changing climate and the invasion of European heather (Calluna vulgaris L.). We collaborated with Ngāti Rangi, a Māori iwi (tribe) who are kaitiaki (guardians) over the park. Access to mātauranga Māori (wisdom/knowledge) via interviews allowed us to identify five ecologically important indigenous plant species that are and taonga (treasured). We surveyed the distribution and density of these focal species and C. vulgaris in the park along elevational and invasion gradients. Data from the surveys was bolstered with publically available occurrence data to model the distribution of C. vulgaris. We then projected the species’ distribution within current and predicted future climate scenarios. In addition to their climatic tolerances, as derived from surveys and occurrence data, we parameterized SDMs for each indigenous focal species using estimates of pairwise competition with C. vulgaris; these were derived from the focal species’ prevalence along the invasion gradient. We then predicted future distributions of focal species based on predicted climate scenarios and C. vulgaris distribution in those climates.
Results/Conclusions
Our SDMs predict that future climates will facilitate both an expansion of the geographic distribution and higher densities of C. vulgaris in Tongariro National Park. These changes are associated with reductions in the distribution and density of ecologically and culturally important focal plant species, indicating a synergism between these two drivers of ecosystem change. Importantly, although indigenous species responded idiosyncratically, SDMs which incorporated both drivers of change generally yielded more negative forecasts for focal species’ distributions than models driven by climatic variables alone.