A study published in early October in the journal Science suggests that human-caused species loss has far-reaching consequences that were previously underestimated. The scientists highlight the fact that the extinction of bird species has not only wiped out ecological roles but also billions of years of unique evolutionary history.
In birds, extinction leads not only to a loss of species diversity but also to the destruction of vital ecological functions that these animals perform in their habitats. This is particularly pronounced in island ecosystems, where the decline is especially dramatic.
Over the last 130,000 years, more than 610 bird species have gone extinct

Over the past 130,000 years, since humans began spreading across the globe, at least 610 bird species have gone extinct. This figure is alarming, but it only tells part of the story. What is often overlooked is the crucial role these birds played in their ecosystems. Birds fulfill numerous important functions: Some control pests by eating insects, others recycle dead material, and some pollinate plants. When these species vanish, these essential tasks disappear with them. The loss of what’s called functional diversity – the different ecological roles that birds play – has far-reaching consequences for the stability and balance of ecosystems.
Tom Matthews, British climate scientist and lead author of the study, explained to EurekAlert!: “In addition to functional diversity each species also carries a certain amount of evolutionary history, therefore when that species becomes extinct, it’s basically like chopping off a branch of the tree of life and all of that associated phylogenetic diversity is also lost.” The study highlights that the impact of species extinction goes far beyond just reducing the number of species. In fact, through the extinction of bird species since the Late Pleistocene, humans have destroyed about seven percent of the global functional diversity of birds and approximately three billion years of evolutionary history.
Island species are especially vulnerable to extinction
The loss of bird species is particularly severe on islands. In these environments, where animals often live in isolation and occupy unique ecological niches, habitat destruction and the introduction of predators like rats and cats have caused especially dramatic extinction events. One prominent example is the island of Mauritius, home to the famous Dodo. Within just a few decades of human settlement, this flightless bird was driven to extinction. A similar fate befell many other bird species, such as the Hawaiian honeycreeper Kauaʻi ʻōʻō, a songbird that was officially declared extinct in 2023.
Island species are often highly vulnerable due to their limited habitats and adaptations to the absence of predators. Many of these birds evolved to become flightless, leaving them defenseless against new predators introduced by humans. “Frugivory is an important function, as in eating the fruits and then moving around, birds will disperse the seeds of the plants the fruits belong to,” Matthews explains. By consuming and dispersing seeds, birds support the reproduction of many plant species. The extinction of such birds triggers a domino effect, endangering plant species that rely on these birds for seed dispersal.
Long-term impacts on biodiversity
The consequences of this loss are not just felt locally. Since birds play a key role in many ecosystems worldwide, these waves of extinction have global ramifications. Studies show that the extinction of bird species also leads to the shrinking of the global avifauna, meaning a reduction in the size and diversity of bird populations. This, in turn, affects other animals, plants, and even the climate. The ability of many plants to adapt to climate change depends on birds spreading their seeds. With fewer birds around, it becomes increasingly difficult for these plants to adjust to changing environmental conditions.
Future projections are even more alarming: over the next two centuries, more than 1,000 bird species could go completely extinct, further exacerbating the loss of functional and phylogenetic diversity. Island ecosystems, once again, are expected to be particularly hard hit, as human activities place the greatest pressure on species in these vulnerable environments.
Restoring the functionality and stability of ecosystems
Matthews and his team emphasize that action must be taken to address the ongoing biodiversity crisis. Their findings demonstrate that it’s not just about protecting individual species but about preserving the entire functionality and stability of ecosystems. This requires targeted conservation efforts, particularly in the most vulnerable regions, such as islands. Here, reintroduction projects and the deliberate restoration of damaged habitats could make a significant difference.
“These results are a timely reminder that the current extinction crisis is not just about species numbers,” warns Matthews. We need to understand which ecological functions are being lost due to extinction and how we can prevent future losses. To mitigate the expected waves of extinctions, global conservation strategies must be developed and implemented. This includes not only protecting endangered bird species but also restoring damaged ecosystems and combating invasive species.
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