Human-caused bird extinctions reduced diversity in functions, unique history, study finds

NEW DELHI: Extinction of bird species caused by humans over the last 1,30,000 years have substantially reduced functional diversity of birds in the environment, a new study has found. The extinction also resulted in a loss of three billion years of unique evolutionary history, it found.
At least 600 bird species, including the ‘Dodo‘ and songbird ‘Kaua’i ‘o’o’, have become extinct because of humans, since the Late Pleistocene — the era between 2.6 million years ago to 11,700 years ago — when modern humans started to spread throughout the world, researchers, led by those at the University of Birmingham, UK, said.
Dodo, related to the pigeon family, was a heavy flightless bird native to the island of Mauritius, while Kaua’i ‘o’o was native to the Hawaiian island of Kaua’i and was declared extinct in 2023.
“About five per cent of known bird species have gone extinct over the past 1,30,000 years, and these species are more distinct in terms of their traits and lineages than would be expected by chance, especially those that went extinct before 1500 CE (the early modern period),” the authors wrote in the study published in the journal Science.
“Species, functional, and phylogenetic diversity losses are greatest on islands,” they said.
The authors said that the loss of functional diversity is significantly larger than that expected based on the number of extinctions and will likely have had far-reaching implications, given the wide range of ecological roles executed by birds.
The study is “vital for setting effective targets for global conservation strategies, as well as ecosystem restoration and rewilding efforts,” lead author Tom Matthews, from the University of Birmingham, said.
“The sheer number of bird species that have become extinct is of course a big part of the extinction crisis but what we also need to focus on is that every species has a job or function within the environment and therefore plays a really important role in its ecosystem,” Matthews said.
Consequences of loss of functional diversity involve a reduced flower pollination, seed dispersal and a breakdown of control over insect populations, including many disease-causing ones, the authors said.
Some birds control pests by eating insects, scavenger birds recycle dead matter, others eat fruit and disperse the seeds enabling more plants and trees to grow, and some, like hummingbirds, are very important pollinators, Matthews said.
According to him, when those species die, the important role that they play (the functional diversity) dies with them.
Additionally, each species is also known to carry a part of evolutionary history, he said.
“Therefore, when that species becomes extinct, it’s basically like chopping off a branch of the tree of life and all of that associated (evolutionary) diversity is also lost,” he said.
The study’s findings are a timely reminder that the extinction crisis does not merely concern species numbers and that we need to prepare for the loss of a projected 1,000 bird species expected to go extinct over the next two centuries, Matthews added.