KUALA LUMPUR (AFP) - Populations of bees, butterflies and other species important for agricultural pollination are declining, posing potential risks to major world crops, a United Nations body on biodiversity said on Friday (Feb 26).

"Many wild bees and butterflies have been declining in abundance, occurrence and diversity at local and regional scales in Northwest Europe and North America," said an assessment by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).

It said declines also had been detected elsewhere in the world and that possible causes include habitat loss, pesticides, pollution, invasive species, pathogens and climate change.

The report by the IPBES, which was established under UN auspices in 2012 to assess the state of ecosystems and biodiversity, stopped short of declaring a full-scale threat to food supplies but stressed the importance of protecting pollinators to ensure stable fruit and vegetable output.

It said animal pollination is directly responsible for between 5 per cent and 8 per cent of global agricultural production by volume, amounting to between US$235 billion and US$577 billion (S$329 billion and S$808 billion) worth of annual output.

More than three-quarters of the "leading types of global food crops" rely to some extent on animal pollination for yield and quality, it added, giving no details.

"Pollinator-dependent species encompass many fruit, vegetable, seed, nut and oil crops, which supply major proportions of micronutrients, vitamins, and minerals in the human diet," the IPBES said.