Spatial priorities for freshwater biodiversity conservation in light of catchment protection and connectivity in Europe

Turkish Thrace), in S Ukraine and in central and S Russia had high irreplaceability and low protection (Fig 3A and 3B). In contrast, catchments in S Europe generally had high irreplace- ability and high protection, those in NW Europe had low irreplaceability and high protection, whereas catchments in NE Europe had low irreplaceability and low protection (Fig 3A and 3B). There was a weak positive relationship between the proportion of protected areas and irre- placeability (no connectivity: slope 170.7 ± 10.11; r = 0.122; n = 18,816; p < 0.0001; with con- nectivity: slope 217.1 ± 11.23; r = 0.140; n = 18,816; p < 0.0001). The residuals from these regressions confirmed that catchments in the W Balkans, S Ukraine and S Russia had higher irreplaceability than predicted based protection level (Fig 3C and 3D). Catchments with lower irreplaceability than predicted were in N Europe and in central and S Europe (Fig 3C and 3D). Catchments on the Iberian peninsula showed a particularly mixed pattern, whereas smaller residuals showed adequately protected catchments in central Europe and the E Balkans but less so in N Italy and SW France (Fig 3C and 3D). Finally, deviations from the ideal 1:1000 line showed high irreplaceability and low protec- tion in most catchments south of the 49˚ latitude (i.e., Upper Danube), and in the lower Volga and Lake Ladoga (Fig 3E and 3F). The majority of catchments N from the 49˚ latitude did not show large deviations (Fig 3E and 3F), indicating more or less adequate protection. In con-

trast, many catchments in northern Europe showed negative deviations, i.e., lower irreplace- ability than expected based on protection (Fig 3E and 3F), with large deviations especially in N Europe and smaller deviations in central Europe. The addition of connectivity did not influ- ence these patterns in any of the three analyses of correspondence (Fig 3B–3D and 3F). Discussion Our study represents a first attempt at continental-scale conservation prioritization based on a large database of freshwater biodiversity and catchments as planning units, which Fig 1. Conservation priority (irreplaceability) of river and lake catchments in Europe (n = 18,816), estimated as selection frequency in 1000 runs of Marxan in three scenarios (rows), each without connectivity (left) or with connectivity (right). In Scenario 1 (upper row), catchment protection was not considered, whereas well-protected catchments (more than 70% of catchment area protected) were a priori included in Scenario 2 (middle row) and were a priori excluded in Scenario 3 (bottom row). The spatial data for species distributions are deposited in http://project. freshwaterbiodiversity.eu, while the shapefile containing freshwater catchments are available at http://hydrosheds.org/ page/hydrobasins. Spatial information on protected areas were obtained from http://protectedplanet.net and http:// www.eea.europa.eu. The maps were created with ArcGIS 10.0 by ESRI. https://doi.org/10.1371/journal.pone.0267801.g001

Table 1. Number of species of different Red List conservation status for which representation targets were met (Yes) or not met (No) in the three scenarios, each replicated without or with connectivity. Red List status Scenario 1 Scenario 2 Scenario 3 Connectivity Connectivity Connectivity Without With Without With Without With Yes No Yes No Yes No Yes No Yes No Yes No CR 144 9 137 16 147 6 135 18 126 27 107 46 EN 142 5 131 16 144 3 124 23 129 18 111 36 VU 261 7 258 10 262 6 254 14 252 16 232 36 NT 127 0 126 1 127 0 126 1 126 1 126 1 LC 831 3 831 3 832 2 830 4 829 5 828 6 DD 100 2 100 2 100 2 100 2 100 2 99 3 Total 1605 26 1583 48 1612 19 1569 62 1562 69 1503 128 https://doi.org/10.1371/journal.pone.0267801.t001 PLOS ONE Spatial priorities for freshwater biodiversity in Europe PLOS ONE | https://doi.org/10.1371/journal.pone.0267801 May 17, 2022 7 / 15