RURAL NEPAL — Pollinating insects contribute more than 20% of key vitamin intake and pollinate crops accounting for 44% of farm income in rural Nepal, according to a study published Wednesday in the journal Nature. The research warned that a complete loss of pollinators could cut farming income by nearly 50% and reduce vitamin A and folate intake by 20%.

The study tracked the diets of 776 people over the course of a year, with researchers visiting participants' homes twice a week to ask about everything they had eaten in the previous 24 hours. The research team also surveyed farms around villages to record which insects visited which plants and measured how much pollen individual insects carried on their bodies.

Insects, particularly native honeybees, helped produce more than 20% of total vitamin E, vitamin A and folate intake for the communities, while bees and hoverflies were responsible for more than 40% of household income. In rural Nepal, almost three quarters of the population depend directly on smallholder farming.

If insect decline continues on its current trajectory, vitamin A and folate intake could fall by about 7% by 2030 because of fewer pollinators, the study found. Native honeybee populations in parts of Nepal have dropped by nearly 50% over the past decade due to climate change, habitat loss and pesticide use. The researchers estimated that interventions such as planting wildflowers, providing bee nesting sites and reducing pesticides could raise farmer income by up to 30% and lift 9% of the population out of nutrient deficiency.

"The magnitude of the effect surprises me," said Taylor Ricketts, an ecologist at the University of Vermont. "A rounding error, it's not a little effect. It is really in the ball game in keeping people healthy."

Kelvin Mulungu, an agricultural economist at the International Maize and Wheat Improvement Center in Lusaka, Zambia, said: "Biodiversity isn't just about saving bees or wild animals. It's for the benefit of humans and sometimes the most vulnerable populations."

Thomas Timberlake, an ecologist at the University of York, noted the complexity of the findings. "Ecological systems are complex and messy," Timberlake said.