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Loss of natural habitat is a key threat to biodiversity.K. K. MustafahK_K_Mustafah;K_K_Mustafah -

Humans eat 14% of the world’s surviving species of birds. However, this is not the only reason why 48% of the extant bird species are undergoing population decline, a study by nine renowned avian experts and conservationists has revealed.

The State of the World’s Birds , an annual review of environmental resources published on May 5, has attributed the threat to almost half of the 10,994 recognised extant species of birds to the expanding human footprint on the natural world and climate change.

The degradation and loss of natural habitats as well as direct overexploitation of many species are the key threats to avian biodiversity, the study led by the Manchester Metropolitan University (MMU) says.

The use of 37% of the surviving bird species as common or exotic pets and 14% as food are examples of direct overexploitation, the report indicates.

The review found that 5,245 or about 48% of the existing bird species worldwide were known or suspected to be undergoing population decline. While 4,295 or 39% of the species had stable trends, about 7% or 778 species had increasing population trends. The trend of 37 species was unknown.

The study underlines birdwatching, a global pastime involving millions of people, as a form of avian conservation but warns of “local negative impacts” of bird feeding valued at $5-6 billion per year and growing by 4% annually. It reviewed changes in avian biodiversity using data from the International Union for Conservation of Nature’s Red List to reveal the changes in fortunes of all the global bird species.

The caution is for some non-provisioned species via trophic cascades, an “ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling”.

“Avian diversity peaks globally in the tropics and it is there that we also find the highest richness of threatened species. We know a lot less about the fortunes of tropical bird species than we do about temperate ones, but 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,” said MMU’s Alexander Lees, the lead author of the study.

Use of data

The study, which involved scientists from Manchester Metropolitan, Cornell University, Birdlife International, the University of Johannesburg, Pontifical Xavierian University and the India-based Nature Conservation Foundation (NCF), reviewed changes in avian biodiversity using data from the International Union for Conservation of Nature’s Red List to reveal the changes in fortunes of all the global bird species.

Apart from tropical forests, the threat of natural grasslands has been particularly worrying for North America, Europe and India.

“If unique ecosystems like grasslands are to retain their diverse birdlife, governments and research groups must prioritise such landscapes and their inhabitants for conservation and ensure that they do not become plantations or woodlands,” NCF’s Ashwin Viswanathan said.

“After documenting the loss of nearly 3 billion birds in North America alone, it was dismaying to see the same patterns of population declines and extinction occurring globally,” Ken Rosenberg of Cornell University said.

Because birds are highly visible and sensitive indicators of environmental health, we know their loss signals a much wider loss of biodiversity and threat to human health and well-being, he added.

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