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Corresponding author: Paride Balzani ( paride.balzani@unifi.it ) Academic editor: Shana McDermott
© 2022 Paride Balzani, Ross N. Cuthbert, Elizabeta Briski, Bella Galil, Gustavo A. Castellanos-Galindo, Antonín Kouba, Melina Kourantidou, Brian Leung, Ismael Soto, Phillip J. Haubrock.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Balzani P, Cuthbert RN, Briski E, Galil B, Castellanos-Galindo GA, Kouba A, Kourantidou M, Leung B, Soto I, Haubrock PJ (2022) Knowledge needs in economic costs of invasive species facilitated by canalisation. NeoBiota 78: 207-223. https://doi.org/10.3897/neobiota.78.95050
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Canals provide wide-ranging economic benefits, while also serving as corridors for the introduction and spread of aquatic alien species, potentially leading to negative ecological and economic impacts. However, to date, no comprehensive quantifications of the reported economic costs of these species have been done. Here, we used the InvaCost database on the monetary impact of invasive alien species to identify the costs of those facilitated by three major canal systems: the European Inland Canals, Suez Canal, and Panama Canal. While we identified a staggering number of species having spread via these systems, monetary costs have been reported only for a few. A total of $33.6 million in costs have been reported from species linked to European Inland Canals (the fishhook waterflea Cercopagis pengoi and the zebra mussel Dreissena polymorpha) and $8.6 million linked to the Suez Canal (the silver-cheeked toadfish Lagocephalus sceleratus, the lionfish Pterois miles, and the nomad jellyfish Rhopilema nomadica), but no recorded costs were found for species facilitated by the Panama Canal. We thus identified a pervasive lack of information on the monetary costs of invasions facilitated by canals and highlighted the uneven distribution of costs.
aquatic environment, habitat connectivity, inequality, InvaCost, invasive alien species, monetary costs
Aquatic invasive alien species (IAS) are a major threat to biodiversity and ecosystem functioning (
Aquatic IAS spread through multiple vectors and pathways, intentionally or unintentionally, through either active or passive transport. For example, they can escape from confinement (
One of the most important pathways that allow the spread of IAS are canals connecting geographically-isolated aquatic systems (e.g.
This paper aims to quantify the known economic costs associated with IAS considered to have been facilitated by canals, enabling active (i.e. self-moving species) or passive (i.e. hitchhiker species) spread of these species. For this study, we focused on three major canal systems: Suez, Panama, and European Inland Canals (Fig.
Locations of the main canal systems studied (a) the European Inland Canals (b), the Panama Canal (c), and the Suez Canal (d). Red lines represent single canals. As for the European Inland Canals, only the three major canals (the Rhine-Main-Danube Canal, the Volga-Don Canal, and the Volga-Baltic Canal) are represented, for simplicity.
Canals directly connect distinct biogeographic provinces (as in the case with the Suez and Panama Canals) or contiguous seas in the case of the Kiel and the Corinth Canals, whose biota may intermingle freely. While the latter two can be considered of regional importance (in Germany and Greece, respectively), the former two are globally important. Indeed, the Suez Canal connects the Red Sea with the Mediterranean Sea, while the Panama Canal connects the Atlantic Ocean (Caribbean Sea) with the (eastern) Pacific Ocean, allowing ships to avoid circumnavigating Africa and South America, respectively, and reducing travel by thousands of nautical miles. The Suez Canal, a marine sea-level canal, was officially opened as early as 1869 and was recently doubled by creating a new lane (the ‘New Suez Canal’, functionally opened in 2016;
For each canal (Suez, Panama, and European Inland Canals), a detailed list of established IAS reported in the literature to have spread through these pathways, either actively or passively, was compiled by reviewing published papers and datasets (Suppl. material
The most recent version of InvaCost (4.1 as of January 2022) includes 13,553 cost entries (i.e. rows of data entries with monetary costs) of IAS extracted from published peer-reviewed and grey literature. Although there may be costs that have not been captured (e.g. unpublished or outside the search languages), InvaCost offers the most up-to-date compilation of invasion costs and, therefore, constitutes the best tool available to draw parallels with the current state-of-the-art in cost reporting and associated knowledge gaps. However, considering the dynamic nature of the database, the results are subject to changes in the future as new monetary cost data become available for different species, countries, sectors of the economy, and other factors or as the existing cost data are further refined for accuracy. All costs published in the literature and included in the database were converted to 2017 US$ values (see
For this analysis, we filtered cost entries in the InvaCost database by selecting those IAS that were reported to have been facilitated in their invasion as a result of the construction of selected canals (Suez, Panama, and European Inland Canals). Further, we filtered these IAS’ costs by the countries involved in these three canal systems. Since costs of aquatic IAS are often under-reported (
To describe the costs of IAS facilitated by the canals over time, we used the expandYearlyCosts function of the ‘invacost’ package (v0.3-4;
To analyse the costs of invasive alien species that were facilitated by canals (European Inland Canals, Suez Canal, and Panama Canal), we extracted species lists from several publications (see Suppl. material
A total of 34 established species for the European Inland Canals, 411 for the Suez Canal, and 98 for the Panama Canal were listed to have been facilitated in their introduction and spread by these canals. In the InvaCost database, we identified in total 19 database entries: 8 for European Inland Canals and 11 for Suez. By way of contrast, no recorded costs were available for Panama. After expansion, these entries resulted in 34 annualised cost entries, encompassing 5 species (the fishhook waterflea Cercopagis pengoi and the zebra mussel Dreissena polymorpha for the European Inland Canals and the silver-cheeked toadfish Lagocephalus sceleratus, the lionfish Pterois miles, and the nomad jellyfish Rhopilema nomadica for the Suez Canal) for a total of $42.2 million ($33.6 for European Inland Canals and $8.6 for Suez). The most surprising result is that costs were recorded for only a few species facilitated by the three canals (9% for European Inland Canals, 0.5% for the Suez Canal, and none for the Panama Canal), and this seems not to depend upon the choice of the countries that could be affected by canal-facilitated invaders, but by the general lack of costs reported for those species. Indeed, only a few cost records associated with the listed species were present in the entire InvaCost database (12% for European Inland Canals, 5% for Panama, and 1% for Suez), even for distant countries.
Fig.
Proportions of monetary costs (outer circle) and cost entries (inner circle) between canals analysed (i.e. European Inland Canals and Suez Canal), according to the cost descriptors studied: species, affected countries, method reliability, implementation, type of costs and impacted sectors.
Our analysis also revealed an uneven distribution of the recorded costs. Out of the total 26 countries investigated for the European Inland Canals, only the United Kingdom ($33.3 million), Finland (about $146,000), Russia (about $74,000), and Denmark (about $58,000) reported costs associated with canal-facilitated invasive species. Similarly, only Turkey ($5.5 million), Cyprus ($3.1 millions), and Israel (about $59,000) reported economic costs associated with the Suez Canal, out of the total 23 countries considered. Despite the low number of recorded costs, most of them were attributed to the high reliability category ($31.5 million for the European Inland Canals and $8.2 million for the Suez Canal) rather than the low reliability one ($2.1 million for the European Inland Canals and about $459,000 for the Suez Canal).
The total costs were differently attributed to observed and potential costs in the two canal systems. In European Inland Canals, about $16.4 million of observed costs were recorded against about $17.2 million of potential costs (though this latter result is mostly due to a single very high potential cost recorded). In contrast, in the Suez Canal, costs were mostly associated with observed entries ($8.2 million, with two very high costs recorded) rather than potential costs ($0.4 million). As for the type of costs, the recorded costs for the European Inland Canals were mostly attributed to management ($31.4 million), followed by damage ($2.1 million), and mixed (about $55,000). The recorded costs for the Suez Canal, instead, were mainly associated with damage ($5.5 million) and management ($3.1 million). The invasive species associated with the European Inland Canals were recorded to impact multiple sectors: authorities-stakeholders ($24.4 million), environment ($1.9 million), and fishery (about $220,000). Moreover, additional costs were recorded for other sectors (diverse: $6.9 million). Similarly, the invasive species facilitated by the Suez Canal had recorded impacts on authorities-stakeholders (about $0.5 million), fishery ($6.2 million, with two very high reported costs), and public and social welfare ($1.9 million).
Canals are important corridors for many aquatic IAS, as revealed by the long list of established species that we obtained. The connection of multiple water bodies with distinct ecological communities is well-known to have promoted the spread of numerous invaders (
By contrast, the economic benefits arising from commerce through canals such as those examined here can be easily materialised (e.g.
Environmental barriers within the respective canal can nevertheless limit the spread of IAS. For example, the Panama Canal is a freshwater canal (mainly composed of Lake Gatun) that marine species need to cross to invade either side. The similar salinity barrier also applies to the Rhine-Main-Danube Canal and the other European Inland Canals, as freshwater conditions in them should prevent the spread of saline species from the Ponto-Caspian region to the North European seas, and the other way around. However, this barrier can halt only stenohaline species actively spreading or fouling the ship hulls, while not impeding biological invasions through ballast waters and sediments (
Some limitations of this study originate from the species and the countries considered. Indeed, in most cases, it can only be presumed that an invader was facilitated by a canal during its spread, especially for species established for a long time, which could have been introduced or spread through other pathways. Other, not easily disentangled, intricacies can also occur. For example, Ponto-Caspian species were sometimes intentionally introduced after canalisation in Europe to stabilise or enrich these new habitats (
Although we tried to be as inclusive as possible, our results underline the paucity of available data. As such, our estimations should be taken with caution, as complex trading relationships and interconnected introduction pathways meant that not all countries invaded as a consequence of canals could be accounted for, i.e. those not immediately bordering the regions linked by canals and those affected by secondary spread (see fig. 6 in
Knowledge needs in economic costs of invasive species facilitated by canalization
Data type: tables (word file)
Explanation note: Sources used for the extraction of species for each canal system. Countries considered for each canal system.