Spatiotemporal shifts in floristic composition under afforestation and climate variability in the sacred sites of Makkah, Saudi Arabia

This study aimed to detect shifts in the floristic composition of the holy sites of Makkah over the past three decades, with special emphasis on the impact of afforestation and climate change. Results from a study carried out thirty years ago were compared with a contemporary survey (excluding afforested habitats) to isolate the impacts of climate change. An afforested area was compared to a nearby natural habitat to evaluate the effects of afforestation. The results show that the current floristic composition includes 116 species from 81 genera and 36 families. Afforestation significantly changed species composition (J = 0.19), mostly by replacing native desert taxa with invasive and disturbance-tolerant species. In addition, the proportional representation of life forms and chorotypes shifted substantially. Over the previous three decades, there has been a change in the amount of rainfall and the monthly average temperatures. While species richness increased by 90.9% compared to the 1989–1991 survey, (excluding afforested habitats), with high species turnover (82%, calculated as 1 – Jaccard similarity = 0.82) and 66% of the original taxa no longer recorded. Overall, the data show that both afforestation and climate change have significantly altered the floristic structure of the study area, emphasising the importance of management techniques targeted at limiting the establishment and spread of invasive species.