The decline of many bird species due to human activity over the past 130,000 years has significantly diminished the functional diversity of birds, a concept that reflects the variety of roles birds play in the ecosystem. This decline has resulted in a staggering loss of around 3 billion years of distinctive evolutionary history, according to a recent study.
The decline of many bird species due to human activity over the past 130,000 years has significantly diminished the functional diversity of birds—a concept that reflects the variety of roles birds play in the ecosystem.
This loss has led to an estimated loss of about 3 billion years of unique evolutionary history, as outlined in a new study published in Science today.
Although humans have been contributing to a global decrease in species diversity for thousands of years, the effects of historical extinctions on other aspects of biodiversity remain poorly understood. Research from the University of Birmingham brings attention to the serious repercussions of the ongoing biodiversity crisis and the pressing need to recognize the ecological roles that are disappearing due to extinctions.
From the famously extinct Dodo to the recently declared extinct Kauaʻi ʻōʻō songbird in 2023, there is evidence that at least 600 bird species have vanished due to human activities since the Late Pleistocene when modern humans began their global spread. This study, titled ‘The global loss of avian functional and phylogenetic diversity from anthropogenic extinctions,’ utilizes the most comprehensive dataset available on bird extinctions during the Late Pleistocene and Holocene, exploring not just the extinction counts but their broader implications for the planet.
Dr. Tom Matthews, the lead author from the University of Birmingham, stated: “The large number of extinct bird species is certainly a significant aspect of the extinction crisis; however, it’s crucial to recognize that each species has specific roles or functions in the ecosystem. For instance, some birds help manage insect populations as they feed on them, while scavenger birds recycle dead matter, others assist in plant growth by eating fruits and dispersing seeds, and species like hummingbirds are key pollinators. When these species disappear, their ecological roles—this functional diversity—vanish too.
“Moreover, every species contains a certain measure of evolutionary history. Thus, when a species goes extinct, it’s akin to cutting off a branch from the tree of life, resulting in the loss of all the associated phylogenetic diversity.”
The study discovered that the extent of bird extinctions caused by humans has led to a loss of around 3 billion years of unique evolutionary history and a 7% reduction in global avian functional diversity. This loss is much greater than anticipated given the number of extinctions. Considering the wide variety of essential ecological tasks performed by birds, the reduction in avian functional diversity is likely to have far-reaching consequences. These consequences include diminished pollination of flowers, limited seed dispersal, the breakdown of natural controls on insect populations—many of which are pests or carriers of diseases—as well as increased disease outbreaks due to less scavenging of carrion. Furthermore, the decline in global bird populations observed in this research is expected to hinder many plant species’ ability to adapt to current and future climate changes.
Dr. Matthews concluded: “These findings serve as an important reminder that the ongoing extinction crisis involves more than just counting species. By highlighting the declines in avian functional and phylogenetic diversity due to human actions, our study underscores the urgent need to comprehend and forecast the effects of past human-induced extinctions on ecosystem functionality. This knowledge is essential for establishing effective targets for global conservation efforts, as well as for ecosystem restoration and rewilding initiatives.”
