Scientists’ warning – The outstanding biodiversity of islands is in peril

Abstract

Despite islands contributing only 6.7% of land surface area, they harbor ~20% of the Earth’s biodiversity, but unfortunately also ~50% of the threatened species and 75% of the known extinctions since the European expansion around the globe. Due to their geological and geographic history and characteristics, islands act simultaneously as cradles of evolutionary diversity and museums of formerly widespread lineages—elements that permit islands to achieve an outstanding endemicity. Nevertheless, the majority of these endemic species are inherently vulnerable due to genetic and demographic factors linked with the way islands are colonized. Here, we stress the great variation of islands in their physical geography (area, isolation, altitude, latitude) and history (age, human colonization, human density). We provide examples of some of the most species rich and iconic insular radiations. Next, we analyze the natural vulnerability of the insular biota, linked to genetic and demographic factors as a result of founder events as well as the typically small population sizes of many island species. We note that, whereas evolution toward island syndromes (including size shifts, derived insular woodiness, altered dispersal ability, loss of defense traits, reduction in clutch size) might have improved the ability of species to thrive under natural conditions on islands, it has simultaneously made island biota disproportionately vulnerable to anthropogenic pressures such as habitat loss, overexploitation, invasive species, and climate change. This has led to the documented extinction of at least 800 insular species in the past 500 years, in addition to the many that had already gone extinct following the arrival of first human colonists on islands in prehistoric times. Finally, we summarize current scientific knowledge on the ongoing biodiversity loss on islands worldwide and express our serious concern that the current trajectory will continue to decimate the unique and irreplaceable natural heritage of the world’s islands. We conclude that drastic actions are urgently needed to bend the curve of the alarming rates of island biodiversity loss.

Ecological and Cultural Understanding as a Basis for Management of a Globally Significant Island Landscape

“…The mining process on K'gari had reduced an advanced dune system with well-developed soil profiles, which can take hundreds or even thousands of years to develop, to the equivalent of a very young dune system, basically consisting purely of unconsolidated silica sands [30]. The areas disturbed by mining are also subject to weed infestations, especially the exotic Lantana (Lantana camara) [30], an extremely adaptable and rapidspreading species capable of inhabiting a wide variety of ecosystems, which has been internationally highlighted as a threat to island biodiversity [31].…”

Genetics Matters: Voyaging from the Past into the Future of Humanity and Sustainability

“…Climate change, one of the defining issues of the 21st century, is predicted to be the cause of extinction for up to 40% of existing species in the next 30 years [ 133 , 134 ]. Biodiversity, as well as evolution and conservation, are becoming increasingly important as a result of climate change and habitat loss that can lead to extinction [ 135 , 136 ]. Facilitated adaptation, where gene variants from a well-adapted population are transferred into the genomes of threatened populations of either the same or different species, has been set forth to mitigate maladaptation and avert extinction.…”

The influence of biotic and abiotic drivers on arthropod co-occurrence network topology in native forest remnants in the Azores

“…Current changes in insect species abundances with numerous extinctions are caused in different degree by habitat loss (including for agriculture), pollution (including pesticides), invasive species, climate change, direct exploitation and co-extinction of dependent species (Wagner 2020, Cardoso et al 2020). Due to their isolated nature and fragile ecosystems, with a high number of endemic species, islands are particularly threatened by these anthropogenic stressors and thus their native species decline at an unprecedented pace (Gillespie and Roderick 2002, Fernández-Palacios et al 2021). Whilst worldwide species declines can stem from a broad range of causes, the majority of threats to native flora and fauna on islands originates from two major sources: disappearing natural habitats due to changes in land use and the introduction of exotic species (Cardoso et al 2010, Triantis et al 2010, Borges et al 2019, Pyšek et al 2020, Fernández-Palacios et al 2021).…”

“…Hence, there is an urgent need to understand how anthropogenic impacts drive changes in interaction networks in order to precisely assess the effect of these altered networks on ecosystem functions. However, despite the considerable amount of research to investigate the anthropogenic impact on island biodiversity (Fernández-Palacios et al 2021), little is known how anthropogenic influence impacts the interactions of species within insular communities. Different examples on how introduced exotic species can encroach indigenous network and sometimes even replace native species have been documented (García et al 2014) though.…”

“…Due to their isolated nature and fragile ecosystems, with a high number of endemic species, islands are particularly threatened by these anthropogenic stressors and thus their native species decline at an unprecedented pace (Gillespie andRoderick 2002, Fernández-Palacios et al 2021). Whilst worldwide species declines can stem from a broad range of causes, the majority of threats to native flora and fauna on islands originates from two major sources: disappearing natural habitats due to changes in land use and the introduction of exotic species (Cardoso et al 2010, Triantis et al 2010, Borges et al 2019, Pyšek et al 2020, Fernández-Palacios et al 2021. Whereas habitat destruction most commonly results in direct loss of species, and is relatively easy to quantify and test its effects, the consequences of spreading exotics are more difficult to study as it requires data on species interactions (Sax et al 2002, Borges et al 2020).…”