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A new study has found that humans have wiped out around 1,400 bird species - twice as many as previously thought, with major implications for the ongoing biodiversity crisis. 

Many of the world's islands were previously untouched paradises, but the arrival of people to places like Hawaii, Tonga and the Azores led, over time, to far-reaching impacts including deforestation, overhunting and the introduction of invasive species. Consequently, bird species were wiped out. 

While the demise of many birds since the 1500s has been recorded, our knowledge of the fate of species before this relies on fossils, and these records are limited because birds' lightweight bones disintegrate over time; this conceals the true extent of global extinctions. 

Researchers now believe 1,430 bird species, almost 12 per cent, have died out over modern human history, since the Late Pleistocene around 130,000 years ago, with the vast majority of them becoming extinct directly or indirectly due to human activity. 

The study, led by the UK Centre for Ecology & Hydrology (UKCEH) and published in Nature Communications, used statistical modelling to estimate the undiscovered bird extinctions. 

Lead author Dr Rob Cooke, an ecological modeller at UKCEH, - "Our study demonstrates there has been a far higher human impact on avian diversity than previously recognised. Humans have rapidly devastated bird populations via habitat loss, overexploitation and the introduction of rats, pigs, cats and dogs that raided nests of birds and competed with them for food. We show that many species became extinct before written records and left no trace, lost from history." 

Dr Søren Faurby of the University of Gothenburg, a co-author of the study, adds: "These historic extinctions have major implications for the current biodiversity crisis. "The world may not only have lost many fascinating birds but also their varied ecological roles, which are likely to have included key functions such as seed dispersal and pollination. This will have had cascading harmful effects on ecosystems so, in addition to bird extinctions, we will have lost a lot of plants and animals that depended on these species for survival." 

Observations and fossils show 640 bird species have been driven extinct since the Late Pleistocene period, 90 per cent of these on islands inhabited by people. These range from the iconic Dodo of Mauritius to the Great Auk of the North Atlantic to the lesser-known Saint Helena Giant Hoopoe. 

Dodo -a painting of the late 1620s by Roelant Savery.  

 

Great Auk - Kelvingrove Art Gallery and Museum, Glasgow

But the researchers estimated there have been further 790 unknown extinctions, meaning a total of 1,430 lost species. 

The scientists say their study has uncovered the largest human-driven vertebrate extinction event in history, during the 14th century, estimating that 570 bird species were lost after people first arrived in the Eastern Pacific, including Hawaii and the Cook Islands, nearly 100 times the natural extinction rate. 

They believe there was also a major extinction event in the ninth century BC, primarily driven by the arrival of people to the Western Pacific, including Fiji and the Mariana Islands, as well as the Canary Islands, and highlight the ongoing extinction event, which started in the mid-18th century. Since then, in addition to an increase in deforestation and spread of invasive species, birds have faced the additional human-driven threats of intensive agriculture, pollution and leisure activities.  

Previous research by the authors suggests we are at risk of losing up to 700 additional bird species in the next few hundred years, which would be an unprecedented human-driven decimation of species. But Dr Cooke points out: "Whether or not further bird species will go extinct is up to us. Recent conservation has saved some species and we must now increase efforts to protect birds, with habitat restoration led by local communities." 

The study team based their modelled estimates on known extinctions and the extent of relevant research effort in regions compared to New Zealand. The country is the only place in the world where the pre-human bird fauna is believed to be completely known, with well-preserved remains of all birds there. The fewer studies in a region, the more incomplete the fossil record is expected to be, and the greater the number of estimated undiscovered extinctions. 

Journal Reference: Rob Cooke, Ferran Sayol, Tobias Andermann, Tim M. Blackburn, Manuel J. Steinbauer, Alexandre Antonelli, Søren Faurby. Undiscovered bird extinctions obscure the true magnitude of human-driven extinction waves. Nature Communications, 2023.

Saint Helena Giant Hoopoe by Michael Brett-Surman

“The first evidence of the Saint Helena Giant Hoopoe was discovered in 1963 by the British zoologist Philip Ashmole in the Dry Gut sediments east of Saint Helena. Ashmole found a left humerus, but assumed it to be of a Common Hoopoe, due to remarkable similarities to known hoopoe species. However, further research in 1975 by American palaeontologist Storrs L. Olson unearthed more remains, including shoulder parts, skull elements, and the left femur, which prompted a re-examination of the older evidence and the nomination of a new species. The British Museum of Natural History, as of 1977, was in possession of at least one femur from a Saint Helena hoopoe, slightly larger than Olson described in the nominal paper.” 

When current day leaders and politicians are caught out following a crisis, a misdemeanour or a disaster they inevitably repeat the shop-worn phrase “lessons will be learnt”. Sad to say that history teaches us  that lessons are rarely if ever learned and that as a society we just commit the same mistakes over and over again, like lemmings over a cliff.  Given the greed and corruption of modern times it is impossible to see how we can escape further extinctions, including in time, homo sapiens. 

Do enough people care?  No. Follow the money.

Linking at weekend to Eileen's Saturday

Extinct? Who Cares?

“The sixth mass extinction is under way, this time caused by humans. A team of researchers have calculated that species are dying out so quickly that nature's built-in defence mechanism, evolution, cannot keep up. If current conservation efforts are not improved, so many mammal species will become extinct during the next five decades that nature will need 3-5 million years to recover to current biodiversity levels. And that's a best-case scenario.” 

Date: October 15, 2018 

Source: Aarhus University 

"There have been five upheavals over the past 450 million years when the environment on our planet has changed so dramatically that the majority of Earth's plant and animal species became extinct. After each mass extinction, evolution has slowly filled in the gaps with new species. 

The sixth mass extinction is happening now, but this time the extinctions are not being caused by natural disasters; they are the work of humans.  A team of researchers from Aarhus University and the University of Gothenburg has calculated that the extinctions are moving too rapidly for evolution to keep up. 

If mammals diversify at their normal rates, it will still take them 5-7 million years to restore biodiversity to its level before modern humans evolved, and 3-5 million years just to reach current biodiversity levels, according to the analysis, which was published recently in the scientific journal, PNAS." 

Some species are more distinct than others 

"The researchers used their extensive database of mammals, which includes not only species that still exist, but also the hundreds of species that lived in the recent past and became extinct as Homo sapiens spread across the globe. This meant that the researchers could study the full impact of our species on other mammals. 

However, not all species have the same significance. Some extinct animals, such as the Australian leopard-like marsupial lion Thylacoleo, or the strange South American Macrauchenia (imagine a lama with an elephant trunk) were evolutionary distinct lineages and had only few close relatives. When these animals became extinct, they took whole branches of the evolutionary tree of life with them. We not only lost these species, we also lost the unique ecological functions and the millions of years of evolutionary history they represented. 

"Large mammals, or megafauna, such as giant sloths and sabre-toothed tigers, which became extinct about 10,000 years ago, were highly evolutionarily distinct. Since they had few close relatives, their extinctions meant that entire branches of Earth's evolutionary tree were chopped off" says palaeontologist Matt Davis from Aarhus University, who led the study. 

And he adds: "There are hundreds of species of shrew, so they can weather a few extinctions. There were only four species of sabre-toothed tiger; they all went extinct." 

Long waits for replacement rhinos 

"Regenerating 2.5 billion years of evolutionary history is hard enough, but today's mammals are also facing increasing rates of extinction. Critically endangered species such as the black rhino are at high risk of becoming extinct within the next 50 years. Asian elephants, one of only two surviving species of a once mighty mammalian order that included mammoths and mastodons, have less than a 33 percent chance of surviving past this century. 

The researchers incorporated these expected extinctions in their calculations of lost evolutionary history and asked themselves: Can existing mammals naturally regenerate this lost biodiversity? 

Using powerful computers, advanced evolutionary simulations and comprehensive data about evolutionary relationships and body sizes of existing and extinct mammals, the researchers were able to quantify how much evolutionary time would be lost from past and potential future extinctions as well as how long recovery would take. 

The researchers came up with a best-case scenario of the future, where humans have stopped destroying habitats and eradicating species, reducing extinction rates to the low background levels seen in fossils. However, even with this overly optimistic scenario, it will take mammals 3-5 million years just to diversify enough to regenerate the branches of the evolutionary tree that they are expected to lose over the next 50 years. It will take more than 5 million years to regenerate what was lost from giant Ice Age species." 

Prioritizing conservation work 

"Although we once lived in a world of giants: giant beavers, giant armadillos, giant deer, etc., we now live in a world that is becoming increasingly impoverished of large wild mammalian species. The few remaining giants, such as rhinos and elephants, are in danger of being wiped out very rapidly," says Professor Jens-Christian Svenning from Aarhus University, who heads a large research program on megafauna, which includes the study. 

The research team doesn't have only bad news, however. Their data and methods could be used to quickly identify endangered, evolutionarily distinct species, so that we can prioritise conservation efforts, and focus on avoiding the most serious extinctions.

As Matt Davis says: "It is much easier to save biodiversity now than to re-evolve it later."