Nearly half of the planet’s bird species are in decline, according to a definitive report that paints the grimmest picture yet of the destruction of avian life.

The State of the World’s Birds report, which is released every four years by BirdLife International, shows that the expansion and intensification of agriculture is putting pressure on 73% of species. Logging, invasive species, exploitation of natural resources and climate breakdown are the other main threats.

Globally, 49% of bird species are declining, one in eight are threatened with extinction and at least 187 species are confirmed or suspected to have gone extinct since 1500. Most of these have been endemic species living on islands, although there is an increase in birds now going extinct on larger land masses, particularly in tropical regions. In Ethiopia, for example, the conversion of grassland to farmland has caused an 80% decrease in endemic Liben larks since 2007. Just 6% of bird species globally are increasing.

Since 1970, 2.9 billion individual birds (29% of the total) have been destroyed in North America. The picture is just as bleak in other parts of the world – since 1980, 600 million birds (19%) have been destroyed in Europe, with previously abundant species such as the common swift, common snipe and rook among those slipping towards extinction. Europe’s farmland birds have shown the most significant declines: 57% have disappeared as a result of increased mechanisation, use of chemicals and converting land into crops. In Australia, 43% of abundant seabird species have declined between 2000 and 2016.

Dr Stuart Butchart, chief scientist at BirdLife International, said: “We have to stop these declines and start getting on track for recovery. Our future, as well as the world’s birds, depends on it. If we continue to unravel the fabric of life, we’re going to continue to place our own future at threat.”

The report is made up of a compendium of other studies, and because birds are the best-studied group on the planet, it gives an idea of the state of nature more generally. “Birds are useful for telling us about the state of the planet. What they say is that nature is in poor condition, lots of species are in decline,” said Butchart.

Birds are cornerstones of healthy ecosystems, so their disappearance is likely to have myriad negative knock-on effects. Hornbills, for example, disperse large seeds in tropical forests; turkey vultures dispose of organic waste, while seabirds help in the cycle of nutrients between sea and land, keeping coral reefs healthy.

The previous State of the World’s Birds report, released in 2018, found 40% of bird species worldwide in decline.

Wildfires feature more prominently in this report than previous editions, having increased and ravaged previously unaffected habitats. The succession of heatwaves, droughts and floods in recent years will lead to widespread species extinctions if they continue, researchers warn, highlighting the importance of addressing the nature and climate crises at the same time.

Growing evidence links the health of bird populations to human health. Covid-19 is a warning of what could happen if we continue to destroy the natural world, with 70% of zoonotic diseases originating in wildlife. A highly pathogenic variant of avian flu – the result of intensive farming – has driven rapid declines in some bird populations this year. More than 300 outbreaks have been reported in UK seabird colonies.

The report comes ahead of the Cop15 meeting in Montreal in December, a once-in-a-decade opportunity to create new legislation to tackle the biodiversity crisis. Butchart hopes the findings will feed into the final statement from Montreal. “The key action needed now by governments is to make sure a really ambitious and bold global biodiversity framework is adopted. We’ve got to bend this curve, so by 2030 we’re on a mission of being nature positive,” he said.

This means increasing the number and quality of protected areas, conserving remaining habitats and restoring those that have been degraded. Preventing the illegal killing of birds, managing invasive species, reducing fisheries’ bycatch and preventing overexploitation of natural resources will all help.

The report is not all gloom. According to BirdLife, between 21 and 32 bird species would have gone extinct since 1993 without conservation work. It cites the creation of a new seabird haven the size of France in the North Atlantic, estimated to protect 5 million birds.

Juliet Vickery, chief executive of the British Trust for Ornithology, who was not involved in compiling the report, said: “The fact that nearly half of all bird species are declining and one in eight is at risk of extinction reinforces the fact that we are living through a biodiversity crisis. It requires action at every level, from local to global. This carries a strong warning about the health of our natural world.”

Birds in trouble The South American harpy eagle, which stands 1 metre (3 feet) tall and feeds on monkeys and sloths, is one of the world’s largest birds of prey. It was uplisted from near threatened to vulnerable on the International Union for Conservation of Nature (IUCN) red list in 2021 because of a combination of forest loss, hunting, poaching and collisions with power lines. It has declined by 50% in 60 years.

The secretary bird, a raptor from sub-Saharan Africa, went from being vulnerable to endangered in 2020 after habitat degradation driven by the burning of grasslands and intensive livestock grazing. Birds are also captured for the wildlife trade.

The lesser florican, a species endemic to the Indian subcontinent whose males perform leaping rituals to get the attention of females, has declined by 90% in 20 years, mainly because of the loss of grassland habitats and the predation of its chicks by feral dogs. There are believed to be fewer than 1,000 mature individuals left, and it is now critically endangered.

The impressive vocal abilities of the Central American yellow-naped Amazon has made it one of the most sought-after parrots in the pet trade. It has declined by more than 80% in 30 years, mainly due to poaching and the expansion of agriculture, and as of 2022 is critically endangered.

The Bahama warbler was badly affected by Hurricane Dorian in 2019, especially on Grand Bahama, where 95% of its habitat is believed to have been destroyed. It was listed as endangered in 2020.