Consequences of global shipping traffic for marine giants

Shipping routes in the ocean are analogous to terrestrial roads, in that they are regularly used thoroughfares that concentrate the movement of vessels between multiple locations. We applied a terrestrial road ecology framework to examine the ecological impacts of increased global shipping on “marine giants” (ie great whales, basking sharks [Cetorhinus maximus], and whale sharks [Rhincodon typus]). This framework aided in identifying where such “marine roads” and marine giants are likely to interact and the consequences of those interactions. We also reviewed known impacts of shipping routes on these species, and then applied the road ecology framework to detect unknown and potentially threatening processes. In the marine environment, such a framework can be used to incorporate knowledge of existing shipping impacts into management practices, thereby reducing the detrimental effects of future expansion of shipping routes on marine giants. The expansion of trade routes and transport infrastructure in response to globalization is threatening the world's biodiversity (Halpern et al. 2015; Yang et al. 2018), yet research on the effects of this expansion on global biodiversity has primarily focused on the terrestrial realm (Laurance et al. 2009). This is because the emergence of “road ecology” as a discipline originated from attempts to understand the unintended effects of roads on terrestrial ecosystems (Forman et al. 2003). Road ecology focuses on both the direct and indirect impacts of roads by investigating the relationships between road systems and adjacent environments (Coffin 2007), and has been used to identify a number of road‐related consequences for terrestrial wildlife (Alamgir et al. 2017; Laurance and Burgues 2017). For example, roads may directly impact terrestrial wildlife via physical contact (roadkill) or by creating barriers to animal movement, and indirectly by causing wildlife to modify their behavior to avoid roads (Alamgir et al. 2017). Roads also facilitate the expansion of human activity into formerly remote areas, hastening the introduction of anthropogenic impacts (eg pollution, hunting) into previously unaffected environments (Laurance et al. 2009). Like their terrestrial counterparts, marine habitats and species are also threatened by new and existing trade routes (Yang et al. 2018). Shipping routes are essentially “marine roads”, analogous to terrestrial road systems because they provide pathways that facilitate transportation, connect locations, and concentrate vessel movements (Coffin 2007; Laurance et al. 2009). Here, we