A scientific study that claims that the bird population in North America has decreased by around 3 billion in the last 50 years gives the false impression that we are on the eve of a "bird apocalypse," experts say.
Researchers from Cornell University published a paper in the journal last week Science which showed that the bird population of the United States and Canada has fallen by 2.9 billion since 1970.
The decrease represents a 29 percent decrease, according to the study authors.
But others say the study, which was rolled out with a smashing public relations, news media and social media campaign, exaggerated talk of a possible extinction of birds, according to Undark.
That's because most of the bird losses in the study are among the most common species on the planet rather than rare birds, researchers say.
The image above shows a female house sparrow sitting on a wire fence. The sparrow is a species of bird whose population has declined in North America according to experts
An ecologist, Brian McGill from the University of Maine, believes that although the research is largely accurate, it did not mention that 15 percent of the population losses were observed by two species – the European starling and the house sparrow – that are not native to North -America.
"The irony is that land managers and nature conservation authorities have actually spent a lot of money trying to dispel or eliminate the invasive species," McGill said.
McGill also says that the original bird population figures in 1970 may have been blown up after birds migrated to farmland due to deforestation and prairie destruction.
If this is the case, according to McGill this means that the decline mentioned in the Science study is simply a return to an earlier base population that existed before the European birds arrived.
The image above shows a Baltimore Oriole on a branch. Two in five Baltimore Orioles have died since 1970, according to a study published in the journal Science last week
Todd Arnold, a conservation biologist at the University of Minnesota, agreed with McGill.
He said that although he agreed on a decrease in the total bird population, the study should also emphasize that some species saw an increase in the population.
"If you remove the 40 largest decliners from the dataset, hundreds of birds will be left behind, some of which decrease, some of which increase," said Arnold.
"But on average, the rises outweigh the falls."
Arnold said that although experts are rightly concerned about the 40 declining species, "that's not apocalyptic."
"It says that, you know, between 5 and 10 percent of our avifauna is in serious trouble," said Arnold.
"That is a serious message. It may not be "a decline in the North American Avifauna". "
Arnold said the need for smashing headlines and condensed findings in Science magazine probably gave the public a less nuanced picture.
"I'm pretty sure that if I tried the same analysis and focused on the fact that I could make a really cool and advanced analysis based on more than 500 species that would never go beyond the editor's eye, " he said.
"It would have ended up somewhere. But certainly not in science. & # 39;
The lead author of the study, Ken Rosenberg, is an applied natural scientist at the Cornell Lab of Ornithology and the American Bird Conservancy.
He agreed that the study could have added more context and nuance, but due to space constraints "we have to save 90 percent on what we wanted to say."
"Those are very good points (by McGill and Arnold), and you can dive into nuances in many different ways that we couldn't cover in the paper itself," he said.
McGill says that although the overall content of the research is correct, the associated publicity and the talk about & # 39; apocalypse & # 39; can scare people into unbelieving scientists in the future.
The above undated stock image shows a murmur of starlings. Researchers say that although starlings have declined, these birds are native to Europe, not to North America
& # 39; The scientists (who conducted the study) have never claimed that it leads to massive extinction, the scientists have never claimed that it has led to a complete depopulation of birds, & # 39; said McGill of the Science study, & # 39; but that's what people will remember the scientists say in 15 or 20 years. & # 39;
"That's not what really happens," he added.
"I think it damages the credibility of scientists."
& # 39; People are the culprits & # 39;
The researchers who did the study discovered that people are responsible for the decline in bird populations, including factors such as widespread loss of habitat and degradation, widespread use of agrochemicals that eradicate insects vital to the diet of many birds, and even hunting pet cats outside.
"Birds are in crisis," said Peter Marra, director of the Georgetown Environment Initiative at Georgetown University and co-author of the study published in the journal Science.
"The message to take home is that our findings contribute to the increasing evidence with other recent studies showing huge deterioration of insects, amphibians and other taxa, indicating a widespread ecological crisis," Marra added.
"Birds are the essential indicators of environmental health, the canaries in the coal mine, and they tell us that it is urgent to take action to ensure that our planet can continue to support wildlife and humans."
Most losses were not among rare species, but common in almost every bird family and all habitats.
Although the population of birds has generally declined in the United States and Canada, some species, such as birds of prey (left) and woodpeckers (right), have seen an increase in the population according to experts
They include sparrows, swallows, blackbirds, thrush, finch, warbler and meadow larks.
About 90 percent of the total loss came from just 12 bird families and 19 widespread bird species such as the junco with dark eyes, grackle and house sparrow.
Each of those species lost more than 50 million individuals.
The researchers followed populations of 529 species using dozens of bird species on the ground, as well as weather radar data that revealed similar declines in the volume of migratory birds.
Meadow birds were hit particularly hard, with a 53 percent reduction in the population amid intensified agriculture.
Shorebirds, depending on sensitive coastal habitats, underwent a 37 percent decline.
Most shorebirds are migratory and experienced habitat degradation and destruction in many locations where they migrate.
In addition, many shorebirds in Arctic regions are rapidly breeding due to climate change.
The researchers documented a sharp decline for migratory birds. They noticed a major decline in birds migrating to the tropics, where devastating rates of habitat loss and damage have occurred.
Migratory birds are also threatened at their stopover locations and at their North American breeding grounds.
The researchers said other studies have documented worrying losses of birds in other parts of the world.
Meanwhile, Boreal Forst birds such as the evening grosbeak (above) have experienced a steep population decline, experts say
"Birds are an essential part of many ecosystems," said Rosenberg.
"They serve as predators and prey in food webs, distribute seeds and offer ecosystem services such as eating insect pests. When we lose large amounts of birds, we disrupt the entire web of life on which we all depend. & # 39;
Effect of climate change
Although climate change was not the main cause of the population collapse, it is likely to aggravate existing threats to bird populations, Rosenberg said.
The researchers said that the extinction of the passenger pigeon in the early 20th century, once probably the most common birds on earth in the billions, showed that even abundant species can die out quickly.
Some species of birds showed profit. Banning the pesticide DDT caused the resurgence of bird of prey populations, including the bald eagle, the researchers said.
Water bird management policies, including protection and restoration of wetlands, allowed ducks and geese to thrive, she added.
"These are important examples that show that if we choose to make changes and actively manage the threats that birds face, we can have a positive impact on the bird population," Rosenberg said.
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