Dr Martina Treurnicht1,2, Prof Frank M Schurr3, Dr Jasper A Slingsby1,4, Prof Karen J Esler2, Dr Joern Pagel3
1South African Environmental Observation Network (SAEON), Cape Town, South Africa, 2Stellenbosch University, Dept of Conservation Ecology, Stellenbosch, South Africa, 3University of Hohenheim, Landscape Ecology & Vegetation Science, Stuttgart, Germany, 4University of Cape Town, Dept of Biological Sciences, Cape Town, South Africa
The ecological effects of harvesting on natural populations are not well understood. Notably, how plant populations respond to harvesting across species’ entire geographical ranges remain largely unknown. We study geographical variation in sensitivity to wildflower harvesting for 26 Proteaceae species in the Cape Floristic Region (South Africa). We use range-wide demographic data, constituting 3454 population-level records of reproduction and survival, to parameterize dynamic population models and simulate the effects of harvesting across species’ ranges and environmental variation (climate, soil fertility and fire disturbance). To evaluate the persistence and viability of populations to different harvesting levels, we perform extinction risk simulations that predict the population-level intrinsic mean time to extinction. We derive probability of extinction over a 100-year (P100) timeframe to quantify intra- and interspecific variation in sensitivity to harvesting for the study species. Our results show that harvesting generally reduced the future population persistence across species’ ranges. We also detected considerable intra- and interspecific variation in sensitivity across the 26 study species. Intraspecific variation in sensitivity to harvesting showed distinct geographical patterns with high sensitivity at range edges, which was often driven by the climatic extremes of species’ ranges. Our study shows the importance of jointly considering demographic- and environmental variation when assessing sensitivity to harvesting at region-wide scales. Our study should be useful to refine locally and regionally adapted sustainable harvesting guidelines, and help to identify areas for future monitoring to prevent the overexploitation of populations and species in the face of ongoing global change.
I am a plant ecologist studying the relationships between plant performance and the environment as a basis for understanding biodiversity responses to ongoing global change. Notably, I study large-scale demographic- and functional trait variation of multiple species across their geographical distributions in the Cape Floristic Region biodiversity hotspot. Currently, I am intrigued by the life history, demography (e.g. survival and reproduction) and morphological features of the charismatic Cape Proteaceae – the ‘flagship’ plant family of the Cape Floristic Region. By focusing on the demographic and functional trait variation of this plant family, the over-arching goal of my research is to look for efficient and informative approaches to understand the large-scale dynamics of plants in a rapidly changing world.