Quantitative methods of identifying the key nodes in the illegal wildlife trade network

Abstract

Innovative approaches are needed to combat the illegal trade in wildlife. Here, we used network analysis and a new database, HealthMap Wildlife Trade, to identify the key nodes (countries) that support the illegal wildlife trade. We identified key exporters and importers from the number of shipments a country sent and received and from the number of connections a country had to other countries over a given time period. We used flow betweenness centrality measurements to identify key intermediary countries. We found the set of nodes whose removal from the network would cause the maximum disruption to the network. Selecting six nodes would fragment 89.5% of the network for elephants, 92.3% for rhinoceros, and 98.1% for tigers. We then found sets of nodes that would best disseminate an educational message via direct connections through the network. We would need to select 18 nodes to reach 100% of the elephant trade network, 16 nodes for rhinoceros, and 10 for tigers. Although the choice of locations for interventions should be customized for the animal and the goal of the intervention, China was the most frequently selected country for network fragmentation and information dissemination. Identification of key countries will help strategize illegal wildlife trade interventions.wildlife trade | network analysis | key player | elephant | rhinoceros T he illegal wildlife trade is an industry in which thousands of wild animals and associated products are shipped daily around the globe as food, pets, medicines, clothing, trophies, and religious amulets (1, 2). The complex illegal wildlife trade network structure often involves important intermediate stops for bulking or breaking down shipments, switching modes of transport, and manufacturing wildlife byproducts (3-5). Despite advances in wildlife detection technology and general descriptive work on the illegal trade (3, 6-17), current prevention and control approaches are failing (5, 18). More quantitative research has been called for (4,17,19). Accordingly, we take a more analytical approach to identify the key countries involved in the illegal wildlife trade network. Specifically, we use a new database of illegal wildlife trade reports, HealthMap Wildlife Trade (www. healthmap.org/wildlifetrade/), to identify (i) the key exporter, intermediary, and importer countries and (ii) the countries where enforcement activities and educational campaigns might most effectively disrupt the networks. Identifying these key countries can provide useful information on how to allocate resources to combat the illegal trade in wildlife. ResultsWe analyzed a total of 232 international shipments of elephants, 165 shipments of rhinoceros, and 108 shipments of tigers for the period August 2010 to December 2013 after the exclusion of reports due to being duplicates, not providing the countries of origin and destination, or not involving international trading. We excluded 153 shipments for elephants, 170 for rhinoceros, and 197 for tigers (Table S1). Details regarding the sources of the data ...

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