The effect of species extinctions on island biogeographic patterns

Abstract

The study of island systems has provided the basis of much of what we understand about a number of biogeographic patterns. However, islands have also suffered numerous extinctions as a result of human activities. The extent to which these extinctions have influenced the many different patterns we study as island biogeographers, and thus what we consider to be “natural”, is largely unknown. Here, we use a simulation approach to illustrate the impacts of anthropogenic extinctions on various macroecological and biogeographical patterns on islands. We simulated an archipelago consisting of five islands and filled these islands with a realistic set of species, each possessing four functional traits. Using this dataset, we then calculated a number of biogeographic patterns, including the slope of the island species–area relationship, functional richness and beta‐diversity (taxonomic and functional). The next stage of the simulation modeled the colonization of the archipelago by humans, represented by a 50% reduction in the carrying capacity of the archipelago and by an associated wave of species extinctions. When the extinction simulation process was finished, the various metrics were re‐calculated. The results illustrate that all the analyzed patterns are affected to some degree by the human‐induced loss of species. Overall, our results highlight how the extinction of species as a consequence of human actions on islands can influence our interpretation of “natural” island biogeography patterns.

Prioritizing nationally endemic species for conservation

“…Half of these loses have been from islands. Globally, endemic species restricted to islands represent more than 60% of known terrestrial extinctions in the last 500 years (Matthews et al, 2020). Two of the extinctions (Labrador duck and Dawson caribou) were driven by over‐harvest and the remainder resulted from habitat loss or modifications for species that occurred in narrow ranges.…”

“…Of the 938 extinct species and infraspecies (subspecies and varieties) on the IUCN Red List, 93.8% are nationally endemic (IUCN, 2022). While 61% of species listed on the IUCN Red List as extinct were confined to islands (Matthews et al, 2020), a large proportion of global extinctions are also driven by the loss of nationally endemic species from continental nations. For example, in Canada, over one‐third of the species (excluding populations and designatable units) assessed as extinct by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) under the Species at Risk Act (2002) are nationally endemic (Government of Canada, 2021).…”

Threatened and extinct island endemic birds of the world: Distribution, threats and functional diversity

“…Our analyses indicate that CR species in particular are threatened by introduced species, highlighting the urgency required to deal with this issue on many islands before it is too late. While also an issue in continental systems, the effects of biological resource use, and especially hunting, are particularly acute on islands due to the small population sizes of many island endemics coupled with the small nature of the island themselves and thus lack of refugia (Matthews, Leidinger, & Cabral, 2020; Steadman, 2006; Whittaker & Fernández‐Palacios, 2007). While all the aforementioned drivers are detrimental when occurring in isolation, we found that many species are affected by more than one driver and it is likely that certain drivers will interact in a multiplicative fashion (Holdaway & Jacomb, 2000).…”

Anthropocentrism, Ecocentrism and Hunter-Gatherer Societies: A Strong Structurationist Approach to Values and Environmental Change

“…However, it appears likely that human agency, in the form of hunting and habitat disruption, along with other factors such as climate change, did play a role (Araujo et al 2017). The extent of this role is unlikely to be determined with any accuracy, but the likelihood that human beings played a part in such extinctions is supported by substantial evidence from across the world showing the decimation of indigenous species with the arrival of humans on previously uninhabited islands (de Nascimento et al 2020;Diamond 1989;Matthews et al 2020).…”