Appendix 1: Sources and references for vulnerability assessment
1.1 Evidence for exposure (references)
1.1.1 Current impacts attributed to climate change:
Arctic Tern 1 - Changes in prey availability during the breeding season have led to population declines. Though hotter temperatures are known to be associated with prey decline, the contribution of climate change to this decline is still debated- Furness, Robert W. “Responses of seabirds to depletion of food fish stocks.” Journal of Ornithology 148.2 (2007): 247-252. High temperatures around the Shetlands coincided with a sharp drop in sandeel populations and therefore a decrease in tern breeding success. The authors note the mechanism is unclear, and the underlying cause may instead be fishery and predation pressure.
- Lindegren, Martin, et al. “Productivity and recovery of forage fish under climate change and fishing: North Sea sandeel as a case study.” Fisheries Oceanography 27.3 (2018): 212-221. Severe decline in sandeels, which Arctic terns are heavily dependent on in the UK, has led to population declines across the Shetlands. While the drop in sand-eels is linked to climatic conditions, the role of climate change is uncertain. However, sandeel abundance is lower in warmer temperatures, so it is plausible that climate change will have a negative effect on sandeel availability.
- Vigfusdottir, Freydis. Drivers of productivity in a subarctic seabird: Arctic Terns in Iceland. Diss. University of East Anglia, 2012. Increasing sea temperatures around Iceland have been linked to reduced sandeel recruitment, which is the likely cause behind recent population declines
- Petersen, Aevar, et al. “Annual survival of Arctic terns in western Iceland.” Polar Biology 43.11 (2020): 1843-1849. Updated evidence supporting the above study, Arctic terns in Iceland are declining and likely cause is collapse of sandeel populations related to climate change
- Wanless, Sarah, et al. “Long-term changes in breeding phenology at two seabird colonies in the western North Sea.” Ibis 151.2 (2009): 274-285. Arctic terns in UK arriving and breeding earlier. Study focusses on colonies on Firth of Forth, southeast Scotland and the Farne Islands
- Møller, A.P., Flensted-Jensen, E. & Mardal, W. 2006. Rapidly advancing laying date in a seabird and the changing advantage of early reproduction. J. Anim. Ecol. 75: 657–665. Arctic terns in Demark are arriving and breeding earlier. Strong correlation with changes in NAO and temperature.
- Burthe, Sarah J., et al. “Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts.” Marine Ecology Progress Series 507 (2014): 277-295. Tern productivity decreases as sea surface temperature gets higher. Probably due to prey availability, study focusses on seabirds in Forth and Tay region.
- Pakanen, Veli-Matti. “Large scale climate affects the timing of spring arrival but local weather determines the start of breeding in a northern Little Tern (Sternula albifrons) population.” Ornis Fennica 95.4 (2018): 178-184. Little terns are arriving earlier to breeding sites in Finland in correlation with changes in the NAO, however they do not seem to be breeding earlier.
- Ramos, Jaime A., et al. “Relation between climatic factors, diet and reproductive parameters of Little Terns over a decade.” Acta Oecologica 53 (2013): 56-62. Higher temperatures result in fewer sand-smelts, a key prey species of little terns, which results in lower breeding success. Study used a 10-year dataset in Algarve, Portugal.
- Mitchell, I., et al. “Impacts of climate change on seabirds, relevant to the coastal and marine environment around the UK.” (2020): 382-399. Little tern nests in the UK are frequently washed away by tidal surges, which has strongly contributed to successive years of poor breeding and subsequent population decline in the UK. Rising sea levels exacerbates these effects and reduces the amount of safe breeding habitat available.
- Burthe, Sarah J., et al. “Assessing the vulnerability of the marine bird community in the western North Sea to climate change and other anthropogenic impacts.” Marine Ecology Progress Series 507 (2014): 277-295. Tern productivity decreases as sea surface temperature gets higher. Probably due to prey availability, study focusses on seabirds in Forth and Tay region.
- Wanless, Sarah, et al. “Long-term changes in breeding phenology at two seabird colonies in the western North Sea.” Ibis 151.2 (2009): 274-285. Sandwich terns in the Shetlands are arriving and breeding earlier, likely in response to changing environmental cues
- Møller, A. P., et al. “Climate change affects the duration of the reproductive season in birds.” Journal of animal ecology 79.4 (2010): 777-784. Breeding season is now significantly shorter in Denmark than it was in 1970 (by approx. 36 days). This is in correlation with rising spring temperatures, is likely in response to changes in environmental conditions
1.1.2 Change in European range size between present day and 2100:
Using a species distribution model (SDM) we correlated species occurrence during the breeding season with a number of terrestrial and marine environmental variables. Species range data came from the European Breeding Bird Atlas (EBBA2) database. Present-day and 2100 terrestrial data were downloaded from the WorldClim database. We used data from the MRI-ESM2 general circulation model (GCM), which is a high-performing model over Europe. Present-day and 2100 marine data were downloaded from the Bio-Oracle database which averages predictions of marine variables from several different atmospheric-oceanic general circulation models (AOGCMS; for full details see Assis et al., 2017). For the map presented in the summary we used representative concentration pathway (RCP) 4.5, which is an “intermediate” emissions scenario. All data were at 5-minute resolution.
- For Caspian Tern, Roseate Tern, Arctic Tern, Little Tern, and Sandwich Tern we included the following terrestrial variables: Mean temperature of the warmest month, precipitation during breeding season, isolation of landmass, area of landmass, distance to sea
- For Caspian Tern, Roseate Tern, Little Tern, and Sandwich Tern we included the following marine variables: Sea surface temperature (during the winter), salinity, maximum chlorophyll concentration, bathymetry (depth and variance)
After running our model we generated a present-day map where every grid-cell is given a habitat suitability score between 0 and 1, where 1 is very suitable habitat and 0 is not at all suitable. We then compared this with a corresponding map built with 2100 data, and highlighted currently inhabitated areas where 1) suitability drops sharply (i.e. by more than 0.1) and 2) suitability drops below a probability threshold set by the model. Conversely we also highlighted areas where suitability rose sharply and above a given threshold. While a drop in habitat suitability is likely to result in population declines, it is not a certainty, and it does not mean that a population will be extinct in 2100 or that a population is doomed to extinction. With conservation action and careful management, along with changes in human behaviour, such declines may be mitigated or in some cases prevented. For a full explanation of the model see the accompanying ‘Methodology’ document.
Underlying data were downloaded from:- Keller, V., Herrando, S., Voríšek, P., Franch, M., Kipson, M., Milanesi, P., Martí, D., Anton, M., Klvanová, A., Kalyakin, M.V., Bauer, H.-G. & Foppen, R.P.B. (2020). European Breeding Bird Atlas 2: Distribution, Abundance and Change. European Bird Census Council & Lynx Edicions, Barcelona. Source of range data
- Fick, S. E., & Hijmans, R. J. (2017). Worldclim 2: New 1-km spatial resolution climate surfaces for global land areas. International Journal of Climatology. http://worldclim.org/version2. Source of present-day and 2100 terrestrial data.
- Assis, J., Tyberghein, L., Bosch, S., Verbruggen, H., Serrão, E. A., & De Clerck, O. (2018). Bio-ORACLE v2.0: Extending marine data layers for bioclimatic modelling. Global Ecology and Biogeography, 27(3), 277–284. https://doi.org/10.1111/geb.12693. Source of present-day and 2100 marine data
1.1.3 Changes in key prey species:
We first identified the key prey species for each species. This can be variable across a species range, but if available evidence suggested at least one major population is highly dependent on a particular prey species, then typically this species would be included. Lists of prey species were compiled from published sources, then verified and expanded following consultation with conservation practitioners. Afterwards we compiled current and projected maps of prey ranges to assess where key prey species may disappear in the near future. If any of the key species are predicted to vanish or drastically reduce in abundance in the current foraging range a given species, we marked this on the summary map. We used several sources to collate range information, but for preference we used data from COPERNICUS as they include projected abundance. For species where this was not available we used habitat suitability instead. In all cases we used RCP 4.5, which is an “intermediate” emissions scenario. For species in the COPERNICUS database we used the 0.6 maximum sustainable yield parameter, which assumes international co-operation to work towards fish-stock sustainability. Our assessment is therefore relatively conservative in terms of changes in prey species.
Arctic Tern key prey species: sandeel species (Ammodytes marinus and Ammodytes tobianus), herring (Clupea harengus) and stickleback (Gasterosteus aculeatus). This species also preys on small invertebrates (larval fish, shrimp, idotea, et). These are poorly characterised so have not been included in the prey assessment. Prey species list was compiled from:- Hatch, J. J., M. Gochfeld, J. Burger, and E. F. J. Garcia (2020). Arctic Tern (Sterna paradisaea), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.arcter.01
- Eglington, Sarah, and Martin Richard Perrow. Literature review of tern (Sterna & Sternula spp.) foraging ecology. ECON Ecological Consultancy Limited, 2014.
- Shealer, D., J. S. Liechty, A. R. Pierce, P. Pyle, and M. A. Patten (2020). Sandwich Tern (Thalasseus sandvicensis), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.santer1.01
- Eglington, Sarah, and Martin Richard Perrow. Literature review of tern (Sterna & Sternula spp.) foraging ecology. ECON Ecological Consultancy Limited, 2014.
- Green, Elizabeth. “Tern diet in the UK and Ireland: a review of key prey species and potential impacts of climate change.” RSPB Report (2017).
- Eglington, Sarah, and Martin Richard Perrow. Literature review of tern (Sterna & Sternula spp.) foraging ecology. ECON Ecological Consultancy Limited, 2014.
- Shealer, D., J. S. Liechty, A. R. Pierce, P. Pyle, and M. A. Patten (2020). Sandwich Tern (Thalasseus sandvicensis), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.santer1.01
- Eglington, Sarah, and Martin Richard Perrow. Literature review of tern (Sterna & Sternula spp.) foraging ecology. ECON Ecological Consultancy Limited, 2014.
- Cuthbert, F. J. and L. R. Wires (2020). Caspian Tern (Hydroprogne caspia), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.caster1.01
- COPERNICUS. (2021). Fish abundance and catch data for the Northwest European Shelf and Mediterranean Sea from 2006 to 2098 derived from climate projections. https://doi.org/10.24381/cds.39c97304
- Kesner-Reyes, K., Kaschner, K., Kullander, S., Garilao, C., Barile, J., & Froese., R. (2019). AquaMaps: Predicted range maps for aquatic species. In R. Froese & D. Pauly (Eds.), FishBase. https://www.aquamaps.org
1.1.4 Climate change impacts outside of Europe
Caspian Tern Caspian terns in North America have been negatively affected by heatwaves, warming seas, severe storms, and increased frequency of flooding, all of which are linked to climate change.- Suzuki, Yasuko, et al. “Colony connectivity and the rapid growth of a Caspian Tern (Hydroprogne caspia) colony on Alaska’s Copper River Delta, USA.” Waterbirds 42.1 (2019): 1-7.
1.2 Sensitivity (references)
We used a list of candidate traits based on that in Foden & Young (2016) that indicate high sensitivity and identified which, if any, terns possessed. In brief, we consulted published literature as well as expert knowledge and online databases such as Birdlife (http://datazone.birdlife.org/) and Birds of the World (https://birdsoftheworld.org), to assess whether terns have either 1) Specialised habitat and/or microhabitat requirement 2) Environmental tolerances or thresholds (at any life stage) that are likely to be exceeded due to climate change 3) Dependence on environmental triggers that are likely to be disrupted by climate change, 4) Dependence on interspecific interactions that are likely to be disrupted by climate change or 5) High rarity.
For more detail and a full list of traits see:- Foden, W. B., & Young, B. E. (2016). IUCN SSC guidelines for assessing species’ vulnerability to climate change. Version 1.0 (Occasional paper of the IUCN Species Survival Commission No. 59)
1.3 Adaptive capacity (references)
We used a list of candidate traits based on that in Foden & Young (2016) that indicate adaptive capacity and identified which, if any, terns possessed. In brief, we consulted published literature as well as expert knowledge and online databases such as Birdlife (http://datazone.birdlife.org/) and Birds of the World (https://birdsoftheworld.org), to assess whether terns have either: 1) High phenotypic plasticity. 2) High dispersal ability or 3) High evolvability.
For more detail and a full list of traits see:- Foden, W. B., & Young, B. E. (2016). IUCN SSC guidelines for assessing species’ vulnerability to climate change. Version 1.0 (Occasional paper of the IUCN Species Survival Commission No. 59)