Climate change is likely to affect all protected areas, including World Heritage (WH) sites. Biodiversity WH sites, i.e. those inscribed under criterion (ix) or (x), contain outstanding biological processes, threatened species and/or endangered habitats, and the impacts of the emerging threat of climate change could place them in jeopardy. It is therefore imperative to better understand both the severity and the sources of impact, in order to mitigate this with informed, appropriate management responses to ensure that the Outstanding Universal Values (OUV), for which they are inscribed as WH site, remains intact and conserved for future generations.
Thanks to a traits-based climate change vulnerability (CCV) assessment by IUCN's Global Species Programme (Foden et al. 2013), wherein all amphibians, birds, and reef-building warm water corals were assessed for their sensitivity, low adaptability and exposure to climate change - it is now possible to identify, through the lens of these species, the most sensitive and exposed WH sites.
This study aims to undertake a desk-based analysis, using existing CCV assessments, for all natural WH sites, especially those inscribed for their outstanding biodiversity values. In doing so we will enhance our understanding of the climate vulnerability of World Heritage sites in general, as well as individually, in terms of the amphibians, birds and corals species they support.
The results for both amphibians and birds are summarised below. Information on detailed comparisons of each trait and exposure can be found in the analysis workbook. Note that the sample of corals in WH sites is not statistically significant and therefore no further summary is made.
15.0% of amphibian species with ranges falling inside the WH network are vulnerable to climate change, compared to 22.0% of all amphibians that are vulnerable globally, indicating that amphibian species found inside natural WH sites are less vulnerable than those found outside. Similar patterns can be found in each category of sensitivity, low adaptability and exposure, where lower proportions of amphibians score 'high' in WH sites.
19.3% of bird species with ranges falling inside the WH network are vulnerable to climate change, compared to 23.6% vulnerable globally. There seems to be significantly more bird than amphibian species occurring within WH sites in proportion (~70%, compared to 32.4% for amphibians). Notably, however, there are a significant number of bird species with unknown sensitivity, low adaptability and exposure scores. The final result resembles that of amphibians, with lower proportions of bird species scoring 'high' in each vulnerability category occurring inside WH sites, compared with species that do not.
15.4% of amphibian species occurring in biodiversity WH sites are vulnerable to climate change compared to 8% in other natural WH sites. As expected, significantly more species are found in biodiversity WH sites, and comparatively higher proportions of these are climate change vulnerable overall, as well as in each individual vulnerability category.
20.0% of bird species occurring in biodiversity WH sites are vulnerable to climate change compared to 14.7% in other natural WH sites. Across sensitivity, low adaptability and exposure, there seems to be a higher degree of variation between biodiversity sites and other natural sites. Notably, high numbers of bird species have unknown scores, and of those with known scores, most score a 'high' in sensitivity, irrespective of biodiversity WH designation.
WH sites in Latin America and the Caribbean has the highest number and proportion of climate change vulnerable amphibians
WH sites in Latin America and the Caribbean has the highest number and proportion of climate change vulnerable birds.
Information on species occurring inside WH sites remains incomplete at best, with some WH sites lacking species-level data altogether. Moreover, in cases where such information is available, it is often neither standardised nor verified, and in many cases, cannot be linked to other species databases, such as the CCV assessment, without significant efforts (e.g. to reconcile names and/or taxonomic changes). To obtain this information, we instead chose to infer species' presences based on the spatial relationship between species range polygons from the IUCN Red List of Threatened Species and boundaries from the World Database on Protected Areas (WDPA), both of which are spatially explicit.
To this end, a spatial overlay was computed between the two datasets, in order to identify species potentially occurring within WH sites. Species intersecting a small area (absolute small size) and a small proportion (relative small size) of WH sites, were excluded (Hoffman et al. 2010). This removed false positives due to inaccurate and mismatching spatial boundaries, which may be due to the different scales at which polygons had been mapped.
In this analysis, only species distributions with presence code 1-2, origin 1-2 and seasonality 1-3 were considered. This is to ensure species that are possibly extent, introduced, uncertain and extinct are excluded. In the case of birds, range of passage is also excluded. Range polygons were then dissolved to remove the effect of duplicates and double counting. The end result was a non-spatial table with unique pairs of WH sites and species, including their associated attributes.
Using species ID numbers, CCV assessments of amphibians, birds and corals were joined, separately, by the partial overlap table derived from the overlay analysis. This enabled climate change vulnerability information to be transferred, via partially overlapping species, to each World Heritage site. Then, by grouping species CCV scores accordingly, analyses were conducted to examine each WH site individually, as well as to examine the entire WH network as a whole.
More specifically, the following were calculated:
It is possible that the difference to be observed reflects a random sampling process. Therefore, a bootstrap method was utilised for statistical significance testing, where the sample (i.e., species in WH sites), was repeatedly re-sampled with replacement 1,000 times to derive an empirical distribution.
Due to the nature of using spatial boundaries to infer species occurring within WH sites, the resulting inferences rely heavily on the quality, in terms of both accuracy and precision, of the input datasets (the Red List of Threatened Species and the WDPA). It is possible that range polygons/boundaries have been mapped at different scales, and the overlay operation may, therefore, result in artefacts of false overlaps. It is therefore necessary to use a threshold to remove such commissions errors. To this end, a series of sensitivity analyses were carried out to determine the effect of using different thresholds. This approach is not perfect and remains an experiment of trial and testing, but by using such a threshold, 'false positives' should have been considerably reduced.
Furthermore, the fact that Red List species polygons represents Extent of Occurrence (EOO) and not Area of Occupancy (AOO) suggests that, in some cases, even a species with 100% overlap with WH sites may still be absent. This should, however, be very rare, especially for endemic and range-restricted species, due to the general large size of these sites and thus should introduce little error for further analysis.
For several components of the vulnerability assessments (some traits, plus exposure), the upper 25% of species 'scores' assessed under that component were were classified as 'high' (Foden et al. 2013). Because such measures are relative within the taxon of interest, comparisons cannot be made between taxa, and any interpretation or generalisation across taxa would be incorrect and meaningless.
Due to the relative nature of the climate change vulnerability assessments, aggregated results for each WH site, and comparisons between different regions are also relative and therefore only make sense for a given taxon.
Currently, all unknown scores are implicitly treated as if they were 'low'. The effect of this propagates from the very lowest level (for each trait), all the way to the final score. As it currently stands, it represents the most conservative or 'optimistic' scenario in terms of species' vulnerabilities, and this may change when better information is made available.
Foden W. B., Butchart S. H. M., Stuart S. N., Vié J-C., Akçakaya H. R., Angulo A., et al. (2013) Identifying the World's Most Climate Change Vulnerable Species: A Systematic Trait-Based Assessment of all Birds, Amphibians and Corals. PLoS ONE 8(6): e65427. doi:10.1371/journal.pone.0065427
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