Author Description

The fourth work further moves the ballast water regulations forward with integrated analysis with a risk-policy-economic-technology nexus. The work uses a ballast water-borne biological invasion risk assessment model based on a higher-order-network. (1) By quantifying the ballast water treatment efficacy of BWTS under the IMO and stricter global standards, the work reveals that stricter regulation is needed to further reduce invasion risks. Given the revealed uneven distribution risks at different ports, the work finds that regional regulations are needed to target high-risk ports. (2) By cluster analysis, the work reveals both intra- and inter-cluster species introduction pathways and identifies "hub ports" connecting several clusters. Targeting such hub ports is the key to break down the inter-cluster connection not only can protect high-risk ports, but also reduce worldwide risks with lower costs by changing the inter-cluster species introduction pattern. (3) Then the work combines a technology cost model to find the least costly way to compliance different "regional stricter regulatory scenarios" since the new policy may choose different numbers of ports to strictly regulate. By varying the number of higher-risk ports selected to do stricter regulations, the model simulates 4257 policy cases. The work finds the vessel-based method is least costly under the IMO regulations under every policy case, while the port-based method becomes important to lower the compliance cost for stricter regulations. The identifies the threshold of the number of ports regulated more strictly for compliance technology selection: when the number of high-risk ports is smaller than 2882, the port-based method at high-risk ports combining the vessel-based method is the least costly strategy; when the number is larger than 2882, the port-based method at all world ports is least costly. This implies the geopolitical shifts in global ballast water management since the IMO is the agency to re