The story so far: The State of the World’s Birds, an annual review of environmental resources published on May 5 by nine natural sciences and avian specialists across the globe, has revealed that the population of 48% of the 10,994 surviving species of birds is declining. The report led by the Manchester Metropolitan University gives an overview of the changes in the knowledge of avian biodiversity and the extent to which it is imperilled.
What are the key findings of the study?
The study found that 5,245 or about 48% of the existing bird species worldwide are known or suspected to be undergoing population declines. While 4,295 or 39% of the species have stable trends, about 7% or 778 species have increasing population trends. The trend of 37 species was unknown. The study draws from BirdLife International’s latest assessment of all birds for the International Union for Conservation of Nature’s Red List that shows 1,481 or 13.5% species are currently threatened with global extinction. These include 798 species classified as vulnerable, 460 as endangered and 223 as critically endangered while 52 species were considered to be data deficient. About 73% species are estimated to have fewer than 10,000 mature individuals, 40% have fewer than 2,500 mature individuals, and almost 5% have fewer than 50 mature individuals. The bird species are non-randomly threatened across the avian tree of life, with richness of threatened species disproportionately high among families such as parrots, pheasants and allies, albatrosses and allies, rails, cranes, cracids, grebes, megapodes, and pigeons. The more threatened bird species (86.4%) are found in tropical than in temperate latitudes (31.7%), with hotspots for threatened species concentrated in the tropical Andes, southeast Brazil, eastern Himalayas, eastern Madagascar, and Southeast Asian islands.
What is the importance of birds to ecosystems and culture?
Birds are a truly global taxon, with one or more species occupying all habitats across the earth’s terrestrial surface including urban environments with no natural analogues. Birds contribute toward many ecosystem services that either directly or indirectly benefit humanity. These include provisioning, regulating, cultural, and supporting services. The functional role of birds within ecosystems as pollinators, seed-dispersers, ecosystem engineers, scavengers and predators not only facilitate accrual and maintenance of biodiversity but also support human endeavours such as sustainable agriculture via pest control besides aiding other animals to multiply. For instance, coral reef fish productivity has been shown to increase as seabird colonies recovered following rat eradication in the Chagos archipelago. Wild birds and products derived from them are also economically important as food (meat, eggs). Approximately 45% of all extant bird species are used in some way by people, primarily as pets (37%) and for food (14%). The cultural role of birds is perhaps more important than any other taxonomic group, the study says. Beyond its symbolic and artistic values, birdwatching is a global pastime practised by millions of people. Garden bird-feeding is valued at $5-6 billion per year and growing by four per cent annually.
What are the threats contributing to avian biodiversity loss?
The study lists eight factors, topped by land cover and land-use change. The continued growth of human populations and of per capita rates of consumption lead directly to conversion and degradation of primary natural habitats and consequent loss of biodiversity, it says. Although global tree cover increased between 1982 and 2016, including by 95,000 sq. km in the tropical dry forest biome and by 84,000 sq. km in the tropical moist deciduous forest biome, this has been driven by afforestation with plantations (often of non-native species) plus land abandonment in parts of the global North, with net loss in the tropics. The other factors are habitat fragmentation and degradation, especially in the tropics; hunting and trapping with 11 to 36 million birds estimated to be killed or taken illegally in the Mediterranean region alone; the impact of invasive alien species and disease (971 alien bird species introduced accidentally or deliberately to 230 countries over the centuries have affected the native species); infrastructure, energy demands and pollution; agrochemical and pharmaceutical usage (pesticide ingestion kills an estimated 2.7 million birds annually in Canada alone); global trade teleconnections; and climate change.
Can the avian biodiversity loss be stemmed?
Yes. The study says ornithologists have a good understanding of the spatio-temporal patterns of avian diversity compared to many other taxa and the measures needed to slow down and ultimately reverse avian biodiversity loss. “The growing footprint of the human population represents the ultimate driver of most threats to avian biodiversity, so the success of solutions will depend on the degree to which they account for the social context in which they are implemented, and our ability to effect changes in individual and societal attitudes and behaviours. Emerging concepts of conservation social science can inform efforts to address biodiversity loss and to achieve more effective and sustainable conservation outcomes, linking birds to human well-being, sustainability, climate resilience, and environmental justice,” it says.