The investigation and construction of a risk assessment system for alien plants in Shenzhen

The rapid urbanization of Shenzhen, a major city in southern China, has facilitated the introduction and spread of alien plant species, posing a significant threat to local biodiversity. The lack of comprehensive research and risk assessments necessitates the development of a scientific assessment system for systematic evaluation and management. This study aimed to: (1) compile a comprehensive list of alien plants in Shenzhen; (2) develop a pre-assessment and risk assessment system to classify invasion risks; and (3) propose targeted preventive and control measures based on validated assessments. Our survey documented 335 species of alien plants in Shenzhen, which belong to 60 families and 206 genera. These species are mainly concentrated in the families Asteraceae, Amaranthaceae, Poaceae, Solanaceae, Fabaceae, and Euphorbiaceae. The risk assessment system for alien plants in Shenzhen covers five aspects of risk: introduction risk, colonization risk, spread risk, potential harm and impact, and control risk. An integrated assessment system was developed for both plants (not yet introduced and already introduced), with 11 and 12 secondary indicators and 41 and 44 tertiary operational indicators, respectively. Validation using 50 alien plant species demonstrated a perfect alignment between the system’s risk categorizations and pre-defined classifications based on field observations, confirming its reliability. Consequently, recommendations for introduction management are proposed, including risk level classification and differentiated management. This research provides guidance for the monitoring and management of alien plants in Shenzhen.