Human-caused bird extinctions erase 3 billion years of evolution

By Stephen Beech via SWNS

The extinction of birds due to man has caused the loss of three billion years of unique evolutionary history, claims new research.

The true global impact of the loss of hundreds of avian species caused by humans - such as the Dodo - is far greater than expected, say scientists.

They say the wiping out of hundreds of bird species due to human activity over the last 130,000 years has led to "substantial" reductions in avian functional diversity – a measure of the range of different roles and functions that birds undertake within the environment.

It has also resulted in the loss of around three billion years of unique evolutionary history, according to research published in the journal Science.

The study, led by researchers at the University of Birmingham, highlights the "severe consequences" of the ongoing biodiversity crisis - and the urgent need to identify the ecological functions being lost through extinction.

From the well-documented Dodo to the recent Kauaʻi ʻōʻō songbird declared extinct in 2023, scientists currently have evidence of at least 600 bird species having become extinct as a result of man since the Late Pleistocene period when humans started to spread throughout the world.

Using the most comprehensive dataset of all known bird extinctions during the Late Pleistocene and Holocene periods, the study looks beyond the number of extinctions to the wider implications for the planet.

Lead author Dr. Tom Matthews, of 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.

"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.

"When those species die out, the important role that they play - the functional diversity - dies with them.

“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 estimates that the scale of anthropologenic bird extinctions to date has resulted in a loss of around three billion years of unique evolutionary history, and 7% of global avian functional diversity – a significantly larger amount than expected based on the number of extinctions.

Given the range of important ecological roles performed by birds, the research team say that the loss of avian functional diversity in particular will likely have had "far-reaching" implications.

They explained that post-extinction "aftershocks" include reduced flower pollination, reduced seed dispersal, the breakdown of top-down control of insect populations - including many pests and disease vectors - as well as increased disease outbreaks due to reduced consumption of rotting flesh.

The team says that the reduction of avian species around the world documented in the research will also likely affect the ability of many plant species to cope with present and future climate change.

Dr. Matthews said: “These results are a timely reminder that the current extinction crisis is not just about species numbers.

"By identifying declines in avian functional and phylogenetic diversity driven by human actions, our findings highlight the urgent need to understand and predict the impacts of past anthropogenic extinctions on ecosystem function in order to prepare for the magnitude of expected future loss from the projected 1,000 bird species that are expected to die out completely over the next two centuries."

He added: "This information is vital for setting effective targets for global conservation strategies, as well as ecosystem restoration and rewilding efforts.”