Appendix 1: Sources and references for vulnerability assessment
1.1 Evidence for exposure (references)
1.1.1 Current impacts attributed to climate change:
Northern Gannet 1 - Gannets are undertaking longer foraging trips, most likely in response to prey shortages due to climate change. Although this likely increases the energetic costs of foraging, there have so far been no observed impacts on breeding success or mortality.- Davies, Rachel D., et al. “Density-dependent foraging and colony growth in a pelagic seabird species under varying environmental conditions.” Marine Ecology Progress Series 485 (2013): 287-294. Gannets are undertaking longer and longer foraging trips Celtic and Irish Seas. This is presumably due to food shortages closer to the colony, and climate change is likely one driver of this. Colonies are still growing and expanding, but at a slower to colonies elsewhere in the UK. This likely means these colonies will be more sensitive in future to climate change, but at the moment this is not classed as a negative impact.
- Barrett, Robert T., Hallvard Strøm, and Mikhail Melnikov. “On the polar edge: the status of the northern gannet (Morus bassanus) in the Barents Sea in 2015-16.” Polar Research 36.1 (2017): 1390384. Since 2011 gannets have established colonies in the Barents Sea (first on bear island), thought to be associated with a warming of the Barents Sea and the northward spread of common prey species.
- Álvarez, David, and Manuel Antonio F. Pajuelo. “Southern populations of European shag Phalacrocorax a. aristotelis advance their laying date in response to local weather conditions but not to large-scale climate.” Ardeola 58.2 (2011): 239-250. Laying dates for shags in northern Spain have changed drastically, advancing by almost 40 days in only 10 years. This is in correlation with changes in land and ocean temperatures, which is also the most likely reason behind this change in phenology.
- Howells, Richard J., et al. “Pronounced long-term trends in year-round diet composition of the European shag Phalacrocorax aristotelis.” Marine Biology 165.12 (2018): 1-15. Diet composition has changed, most likely in response to climate change. No known impact on population. Study in Isle of May
- Howells, Richard J., et al. “From days to decades: short-and long-term variation in environmental conditions affect offspring diet composition of a marine top predator.” Marine Ecology Progress Series 583 (2017): 227-242. Diet composition has changed, in correlation to climate change and change in sandeel abundance. Study in Isle of May.
- Heubeck, Martin, et al. “Population and breeding dynamics of European Shags Phalacrocorax aristotelis at three major colonies in Shetland, 2001-15.” Seabird 28 (2015): 55-77. Populations in the Shetlands have markedly declined, likely due to high mortality from winter storms. While individual extreme weather events are difficult to attribute to climate change, the frequency and severity of extreme weather events is likely increasing.
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 European Shag, and Northern Gannet 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 European Shag, and Northern Gannet we included the following marine variables: Sea surface temperature (during the winter), salinity, maximum chlorophyll concentration, bathymetry (depth and variance)
Several other variables may strongly influence the distribution ofgannets and cormorantsand it is not possible to include all possible variables in a given model. However the following variables have previously been found to be important to predicting the distribution of gannets and cormorants in Europe: average wind speed during breeding season, sea surface height, seabed substrate, average wind speed during breeding season, presence of stable ocean fronts (or bathymetric proxy). For local assessments of climate change, we recommend these variables are strongly considered. We hope to incorporate these variables into future versions of this guidance document.
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.
Northern Gannet key prey species: herring (Clupea harengus), saithe (Pollachius virens), mackerel (Scomber scombrus), sandeel species (Ammodytes marinus and Ammodytes tobianus), capelin (Mallotus villosus), sprat (Sprattus sprattus), haddock (Melanogrammus aeglefinus) and garfish (Belone belone). This species will also take many other species where available, it will also forage fishery discards. Prey species list was compiled from:- Mowbray, T. B. (2020). Northern Gannet (Morus bassanus), 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.norgan.01
- Le Bot, Tangi, et al. “Fishery discards do not compensate natural prey shortage in Northern gannets from the English Channel.” Biological conservation 236 (2019): 375-384.
- Pettex, Emeline, et al. “Multi-scale foraging variability in Northern gannet (Morus bassanus) fuels potential foraging plasticity.” Marine Biology 159.12 (2012): 2743-2756.
- Hillersøy, Grethe, and Svein-Håkon Lorentsen. “Annual variation in the diet of breeding European shag (Phalacrocorax aristotelis) in Central Norway.” Waterbirds 35.3 (2012): 420-429.
- Lorentsen, Svein-Håkon, Jenny Mattisson, and Signe Christensen-Dalsgaard. “Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics.” Marine Ecology Progress Series 619 (2019): 137-147.
- Harris, M. P., and S. Wanless. “The diet of shags Phalacrocorax aristotelis during the chick-rearing period assessed by three methods.” Bird study 40.2 (1993): 135-139.
- 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
Northern Gannet Marine heatwaves in North America have resulted in wide-spread breeding failure and in some cases temporary desertion of colonies. Most likely because of prey shortages, but heat stress could play a role as well. It is difficult to attribute individual climate events to climate change, but heatwaves are becoming more common and more extreme, and will likely continue to do so. Lack of key prey species (mackerel) due to warmer average marine temperatures and over-exploitation has caused low breeding success in a southern population of gannets in Canada.- Franci, Cynthia D., et al. “Nutritional stress in Northern gannets during an unprecedented low reproductive success year: Can extreme sea surface temperature event and dietary change be the cause?.” Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 181 (2015): 1-8.
- d’Entremont, Kyle JN, et al. “Northern Gannets (Morus bassanus) breeding at their southern limit struggle with prey shortages as a result of warming waters.” ICES Journal of Marine Science 79.1 (2022): 50-60.
- Montevecchi, William A., et al. “Ocean heat wave induces breeding failure at the southern breeding limit of the Northern Gannet Morus bassanus.” Marine Ornithology 49 (2021): 71-78.
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, gannets and cormorants 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 gannets and cormorants 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, gannets and cormorants 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 gannets and cormorants 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)