Holocene palaeoecological archives of Eastern Mediterranean plant diversity: Past, present and future trends

The Mediterranean Basin is an environmental change hotspot that, relative to other regions of the world, is forecasted to experience a significant shift in biodiversity due to multiple factors such as climate change and agricultural intensification. Within this framework, the Eastern Mediterranean region is projected to face a temperature rise of ∼3.5–7 °C by 2070–2099 which will result in severe heat stress and freshwater scarcity, along with increased human impacts due to pronounced demographic growth. To assess the impact of environmental and human pressures on plant diversity, we studied the evolution of this major constituent of biodiversity in the Eastern Mediterranean over 8000 years. Our analysis demonstrates that plant diversity has been impacted by long-term (e.g. multi-millennial scale) changes in temperature, precipitation and anthropogenic activities. We identified a tipping point for each of these drivers, showing that Eastern Mediterranean plant diversity has already exceeded its tipping point for precipitation (threshold: 376 ± 17 mm for winter), while it has already attained its critical threshold for temperature (threshold: 1.33 ± 0.5 °C) and anthropogenic activities (threshold: −1.05 ± 0.4 - low to medium pressures). This suggests that the region’s vegetation will probably progressively give way to species that are better suited and more resilient to the changing environmental conditions.