The Terrestrial Island Biodiversity Conundrum

Excerpt from sdg.iisd.org

• Future global biodiversity may be intrinsically linked to the adaptive and resilience capacities of island ecosystems.
• Yet, terrestrial biodiversity of islands is often under-represented within climate change impact assessments, being largely overshadowed by a focus on marine diversity, especially coral reefs.
• Unconstrained habitat destruction and degradation cannot be sustained and will be to the detriment of both island communities and the local biodiversity upon which these communities depend.

Islands across the world (with the exception of Greenland) cover approximately two to four percent of the Earth’s terrestrial surface, yet, oceanic and some continental-shelf islands (many of which are Small Island Developing States (SIDS) are estimated to harbor more than 20% of existing species (e.g., ~25% extant global flora) (Wetzel, 2013; Kumar and Tehrany, 2017). This is largely due to exceptionally high rates of insular terrestrial endemism — averaging around 9.5 times higher for vascular plants and 8.1 times higher for vertebrates than continents (Bellard, 2014; Wetzel, 2013).

However, up to 80% of historical extinctions (Wetzel, 2013) and almost half of all species currently considered to be at risk of extinction occur on islands; with these primarily due to human-induced factors such as invasive species, overexploitation, and habitat loss (Spatz et al. 2017). Now, with the exacerbating impacts of climate change being added to the mix, current projections suggest that further losses could contribute disproportionally to global biodiversity decline (Pouteau and Birnbaum 2016). Hence, future global biodiversity may be intrinsically linked to the adaptive and resilience capacities of island ecosystems.

Yet, terrestrial biodiversity of islands is often under-represented within climate change impact assessments, being largely overshadowed by a focus on marine diversity, especially coral reefs. This is a brief overview of the terrestrial island biodiversity conundrum.