A recent study published in Science Advances reveals that human-driven bird extinctions, caused by habitat destruction or climate change, are resulting in a decrease in functional diversity on islands worldwide. The loss of these species cannot be compensated by introducing non-native birds, even in cases where they exceed the number of extinct species on the island. The lead author of the study, Ferran Sayol, explains that humans have significantly altered bird communities through extinction and introduction of new species across the world. While there has been some discussion about the possibility of introduced species filling the roles of extinct ones, the study found that this is unfortunately not the case.
Sayol and his team conducted a study on 1,302 bird species found in nine different archipelagos. They looked at 265 extinct species and 355 new introductions from 143 separate species. The study revealed that before human arrival, the island bird communities had greater morphological diversity. Unfortunately, human-driven extinctions have disproportionately affected certain types of birds, resulting in the loss of specific ecological roles.
According to Sayol, there were certain extinct bird species that played a significant role in their ecosystem, and these roles have not been taken up by other birds. For instance, the moas of New Zealand and the elephant birds of Madagascar were giant flightless species that acted as large terrestrial herbivores, grazing on vegetation like cattle and sheep do on land. However, humans caused their extinction.
According to scientists, the extinction of birds can lead to the loss of important functions such as pollination and seed dispersal, which can harm other species in a domino effect. Moreover, the loss of native birds due to extinction has resulted in archipelagos becoming more alike in terms of trait diversity as similar species of non-native birds are introduced into different locations. Certain bird groups, including parrots and starlings, have been particularly successful in establishing themselves in areas outside of their natural habitat. Therefore, it is important for conservation efforts to prioritize protecting functionally distinct threatened species in order to prevent further harmful losses to biodiversity caused by human activity.