According to a recent study headed by UCL and University of Gothenburg researchers, human-caused bird extinctions are driving losses of functional diversity on islands throughout the world, and the gaps they leave behind are not being replaced by introduced (alien) species.
The study, which was published in Science Advances, demonstrates how human influences like habitat degradation and climate change are depleting ecosystems, even on islands where alien birds outweigh extinct species.
Lead author Dr. Ferran Sayol (UCL Centre for Biodiversity & Environment Research, UCL Biosciences), who began the research while based at the University of Gothenburg, said: “Humans have drastically changed bird communities, not only by driving animals to extinction but also by introducing species into new habitats across the globe. There has been some debate as to whether introduced species might replace the roles of the extinct species, thus maintaining functional diversity within the ecosystem; here, we found that is unfortunately not the case.”
Some of the extinct species played an ecological role that has yet to be filled by other birds. Before humans drove several gigantic flightless animals extinct, such as New Zealand’s moas and Madagascar’s elephant birds, they were presumably behaving as big terrestrial herbivores as grazers, akin to ungulates like cattle and sheep on the continents.
Other important services that may be lost as a result of bird extinctions include pollination and seed dispersion, both of which can have severe consequences for other species.
Humans have drastically changed bird communities, not only by driving animals to extinction but also by introducing species into new habitats across the globe. There has been some debate as to whether introduced species might replace the roles of the extinct species, thus maintaining functional diversity within the ecosystem; here, we found that is unfortunately not the case.
Dr. Ferran Sayol
The researchers gathered a thorough inventory of all bird species that were present in nine archipelagos before and after human-caused extinctions for this study. This included 355 established invasions from 143 different species and 1,302 avian species, including 265 globally or locally extinct species.
In addition, the researchers measured multiple physical features in skin and bone specimens at several museums, including the Natural History Museum. The researchers were able to measure trait diversity before and after bird extinctions, as well as determine the ecological niches these extinct birds formerly occupied, using this information.
The researchers discovered that island bird groups were more morphologically varied before humans arrived. Their findings illustrate how human-caused extinctions have disproportionately impacted specific bird species (for example, bigger birds and flightless birds are more likely to become extinct), resulting in the loss of ecological roles.
The researchers also discovered that when local birds become extinct and the same types of invasive species get established in multiple areas, archipelagos are becoming increasingly similar in terms of trait diversity.
Co-author Professor Tim Blackburn (UCL Centre for Biodiversity & Environment Research and the Institute of Zoology, ZSL) said: “Some groups of birds have been particularly successful at establishing outside their natural areas for example, many species of parrot and starling. Because of this, islands are becoming more homogeneous as the same kind of birds are established everywhere.”
Co-author Dr. Alex Pigot (UCL Centre for Biodiversity & Environment Research) said: “Our findings add to evidence that conservation efforts should be focused on preserving functionally distinct threatened species, to stem the tide of harmful losses to biodiversity that are driven by human actions. Huge numbers of species are being driven to extinction by human-driven effects such as habitat loss and climate change, so it is vital that we act now to reduce our negative impact on global biodiversity.”
Researchers from UCL, University of Gothenburg, Zoological Society of London, Imperial College London, Royal Botanic Gardens, Kew, and the University of Bayreuth collaborated on the study, which was funded by the Swedish Research Council and Carl Tryggers Stiftelse för Vetenskaplig Forskning, as well as three SYNTHESYS grants from the European Union.
Hawaii, Cuba and Jamaica, Bermuda, Saint Helena, Canary Islands, Madagascar, Mascarene Islands, New Caledonia, and New Zealand were all included in the research.
