Recent trend reversal for declining European seagrass meadows
de los Santos et al., 2019
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a Extent trajectories All species
No change Zostera Zostera noltei marina Increasing Declining 11 10 41 17 138 33 Posidonia Cymodocea oceanica nodosa 2 45 6 70 28 9
b Density trajectories All species
Zostera Zostera Declining No change noltei marina 18 16 16 16 Increasing 9 23 Posidonia Cymodocea oceanica nodosa 4 65 127 6 21 64
Supplementary Figure 1. Distribution of compiled seagrass sites in Europe and their trajectories. Seagrass sites in Europe showing no change (yellow circles, n = 68 for extent and n = 163 for density), increase (green circles, n = 65 for extent and n = 102 for density), and decline (magenta circles, n = 277 for extent and n = 120 for density) trajectories between 1869 and 2016 for (A) extent metrics (occurrence, area, depth limits) and (B) density metrics (cover, shoot density, biomass). Pie charts show the overall and species-specific frequencies of trajectories. Number of sites per trajectories for each species is given next to the pie charts. Trajectories are based on the available time-series reports and thus correspond to different time windows. 2
Area losses Area gains 0.3
0.2 Density
0.1
0.0 10-2 100 102 104
Change in area (ha) Supplementary Figure 2. Changes in seagrass area for the compiled sites in Europe. Density plots for the losses (magenta, n = 136) and gains (green, n = 56) in area of European seagrasses compiled between 1869 and 2016. Note the log10 x-scale.
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Cymodocea nodosa Posidonia oceanica 0 1 3 3 2 0 0 0 0 3 7 50 3 4 9 9 13 0 5 2 4 9 6
25 ) 1 - 0
-25
-50 Zostera marina Zostera noltei 7 11 7 7 10 17 1 0 2 5 9 16 50 8 11 18 26 24 17 2 4 19 21 15 13 R t f d li
25 Decadal rate of change of area (% dec
0
-25
-50 1950s 1960s 1970s 1980s 1990s 2000s 1950s 1960s 1970s 1980s 1990s 2000s Supplementary Figure 3. Decadal rate of change of area of European seagrass species (1950s – 2000s). Decadal analysis includes time-series > 8 years. Number of sites per decade and trajectory are given at the top of the plot.
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Supplementary Table 1. Nature of the combination of multiple causes in documented seagrass losses.
Cause 1 Cause 2 Cause 3 N Coastal modification Extreme events 1 Coastal modification Mechanical damage 3 Extreme events Mechanical damage 2 Extreme events Overgrazing 2 Extreme events Algae invasion 1 Mechanical damage Algae invasion 1 Water quality degradation Coastal modification 7 Water quality degradation Extreme events 1 Water quality degradation Mechanical damage 3 Water quality degradation Overgrazing 1 Coastal modification Extreme events Mechanical damage 1 Water quality degradation Coastal modification Extreme events 2 Water quality degradation Coastal modification Mechanical damage 1 Water quality degradation Coastal modification Wasting disease 1 N: number of sites reported per each combination.
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