48% of bird species declining globally; 50% declining strongly in India
Populations of almost half of all bird species are declining globally because of human influenced factors such as loss or degradation of habitats, changes in land use, overexploitation, and climate change, new research has found.
Around 48% of bird species worldwide are known or suspected to be undergoing population declines, according to State of World’s Birds report published on May 5 in the Annual Review of Environment and Resources, a peer-reviewed journal.
This is in contrast to trends in 39% of species where numbers are stable, and 6% showing increasing population trends, said the study led by Alexander Lees of the Department of Natural Sciences, Manchester Metropolitan University.
The loss in avian diversity is no less alarming in India, where current annual trends available for the past five years have been estimated for 146 species. Of these, nearly 80% are declining in numbers, and almost 50% plummetting strongly. Just over 6% of the species studied show stable populations and 14% show increasing population trends.
The latest study refers to the 2020 State of India’s Birds report that complied and analysed data from over 15,500 birdwatchers and was curated by 140 volunteer editors.
“Avian diversity peaks globally in the tropics, and it is there that we also find the highest richness of threatened species,” lead author Lees said in a statement. “We are now witnessing the first signs of a new wave of extinctions of continentally distributed bird species, which has followed the historic loss of species on islands like the Dodo.”
The Indian report had found that endemic species, birds of prey, and those dwelling in forests and grasslands were the most threatened.
Although there are no confirmed recent continental extinctions in Asia, numerous threatened species have not been seen in recent years, the new research said. For example, the critically endangered Jerdon’s Courser, endemic to the Eastern Ghats in India, has not been seen since 2009.
Detailed information on population changes in common birds was still patchy, with the best data coming from North America and Europe, the study said.
Around 57% of North American species are recording declining trends (303 out of 529 species), a net loss of almost 3 billion birds since 1970, the study found. The situation is similar in the European Union, where trends across 378 species indicate an overall decrease in breeding bird abundance of 17-19% between 1980 and 2017, which translates into a net loss of 560-620 million individuals.
In North America, long-distance migratory species have been badly affected. Farmland species in Europe have declined precipitously by 57% since 1980, driven by agricultural intensification, the paper said.
The study found that bird species and abundance data from the tropics is scarce but in many countries such as India, citizen science driven data was available.
“For example, long-term trends were estimated with sufficient confidence for 146 species in India, of which nearly 80% were found to be declining (50% of these declining strongly), while just over 6% had stable population trajectories, and 14% of species exhibited increasing population trends,” the paper said.
The study also referred to a graph from the Indian report that showed a 62% decline in forest species since before 2000, 59% decline in grassland and shrub species, and 47% decline in wetland species.
The paper flagged the threat of hunting and trapping in different parts of the world, including northeast India. It also said that for some species, like the critically endangered Great Indian Bustard, power transmission lines represent the most significant threat.
“If unique ecosystems like grasslands are to retain their diverse birdlife into the future, both governments and research groups must prioritize such landscapes and their inhabitants for conservation and ensure that they do not become plantations or woodlands,” Ashwin Viswanathan, a researcher at the Mysuru-based Nature Conservation Foundation, said in a statement.
“Many metrics of avian biodiversity are exhibiting globally consistent negative trends, with the International Union for Conservation of Nature’s Red List Index showing a steady deterioration in the conservation status of the global avifauna over the past three decades,” the study said.
As many as 1,481 species (13.5% of 10,994 recognized species) are currently threatened with global extinction, according to BirdLife International’s latest assessment of all birds for the International Union for Conservation of Nature Red List. These include 798 classified as vulnerable (7%), 460 as endangered (4%), and 223 as critically endangered (2%).
More threatened bird species (86.4%) are found in tropical than in temperate latitudes, with hot spots for threatened species concentrated in the tropical Andes, southeast Brazil, eastern Himalayas, eastern Madagascar, and southeast Asian islands, the research found.
The paper recommended conducting reliable estimates of population abundance and change; novel and more effective solutions applied at scale for demand reduction for over harvested wild birds; monitoring green energy transitions that can impact birds if inappropriately implemented; eradication of populations of invasive alien species, and shifting human societies to economically sustainable development pathways, among others, to deal with bird diversity loss.
“We are seeing bird numbers and diversity declining every year during our annual bird day counts,” said Nikhil Devasar, a birdwatcher and author. “We see it happening in the national capital region.”