The metaphor of the butterfly effect, for how tiny, almost imperceptible changes may lead to massive outcomes, is often used in the discussion of chaos theory: a butterfly flaps its wings in Brazil and three months later there’s a sweeping forest fire in India. Well, it turns out butterflies, along with other pollinators, can cause massive outcomes not just by their presence, but also by their absence.

A new modelling study in Environmental Health Perspectives estimates that half a million people are currently dying prematurely every year due to global insect pollinator decline, because of its impact on availability and price of healthy foods such as nuts, legumes, fruits and vegetables. And the researchers said their estimate is “conservative.”

“Today’s estimated health impacts of insufficient pollination would be comparable to other major global risk factors: those attributable to substance use disorders, interpersonal violence, or prostate cancer,” the researchers wrote.

The researchers arrived at their estimate by first turning to work published in Science in 2016 that estimated how much of the agricultural production yield gap – the gap between average farms and those bringing in the most crops – was due to insufficient pollination. That study tracked 344 fields of crops depending on 33 insect pollinators around the world, finding that around one-quarter of the yield gap was likely linked to lost pollinators.

Using that 2016 data, the team estimated that globally declining pollinators have caused a drop in 4.7% of fruit and nut production and 3.2% of vegetables. They then worked to untangle what the world would look like if those pollinators were still here. Where would the extra yield of fruit, nuts and vegetables end up? How would it impact prices? And, finally, how would consumption of those lost foods affect health both worldwide and in every country?

“We estimated how eating more of these healthy foods would benefit health, based on robust epidemiological research that has linked higher fruit, vegetable and nut intake to lowered mortality from many major chronic diseases like heart diseases, stroke, cancers, and diabetes,” said lead author Matthew Smith, a researcher at Harvard’s Department of Environmental Health.

A bee collecting nectar and pollen. That study tracked 344 crop fields depending on 33 insect pollinators around the world, finding that around one-quarter of the cropland yield gap (the gap between average farms and those bringing in the most crops) was likely linked to lost pollinators. Credit: Dustin Humes/Unsplash (Unsplash License)

The world’s pollinators are vanishing for a host of reasons, but the largest is loss of habitat. Other escalating impacts include the use of pesticides and climate change. While many animals are pollinators, including mammals, birds and even some reptiles, this study focused on insect pollinators, which are the vast majority of pollinators for human food.

“The many ways that declining biodiversity is, and will, impact human health and food availability is an important area of knowledge that often gets overlooked in coverage of biodiversity decline,” said Manu Saunders, an entomologist at the University of New England in Australia, who was not involved in the study.

Nation by nation

The researchers not only broke down the impact of pollinator decline globally, but at national levels as well.

Middle-income nations, such as Russia, China and India, were among the hardest hit, especially where there is already a high propensity of mortality due to chronic illnesses, such as cancer, diabetes or strokes. Wealthy countries were more immune from pollinator decline, because many in those countries can still afford fruit, vegetables and nuts even if prices rise.

Surprisingly, some of the regions least hit by pollinator decline are those most impacted by food insecurity, such as parts of Latin America and sub-Saharan Africa.

“Many tropical countries are lower-income, so even if food production increased, they may not eat much more, because it continues to be unaffordable,” Smith explained. “Furthermore, low and lower-middle income countries tend to have lower rates of chronic disease compared with wealthier countries. This is why much of sub-Saharan Africa and Latin America is insulated from the worst of this effect.”

However, this doesn’t mean that all tropical countries are more immune to the impacts. For example, some of the world’s hardest-hit nations, according to the study, include Indonesia, Vietnam and Myanmar. Smith said fruit consumption in these countries has dropped by 7%-15% due to pollinator decline (higher than the global average), while the same countries suffer from significantly higher rates of stroke than the global average.

“[S]troke is by far the most potent link among disease outcomes associated with low fruit intake,” Smith explained.

Fewer pollinators mean less access to fruit, resulting in more strokes in parts of the world where strokes are already a common cause of death. This example shows how pollinator loss may not degrade every aspect of human health, but if it worsens an already outsized health risk in a population, it can have major impacts.

A bee and a fly on flowers. Researchers estimate that globally declining pollinators have caused a drop in 4.7% of fruit and nut production and 3.2% of vegetables. Credit: cocoparisienne/Pixabay (Content License)

“Note that no single factor or input in the food production system can be isolated as ‘the cause’ of a particular issue of concern,” Saunders cautioned, pointing to the complexity of food production, economics and disease interrelationships. “Lack of pollination can occur for many interacting reasons, regardless of whether local pollinator biodiversity is declining.”

Smith readily admitted that “of course, there are uncertainties that accompany our estimates,” something that is typical of any modelling study of a complex system.

He added, “however, we believe that the [findings] give a sense of the magnitude of the effect, on the order of hundreds of thousands of excess deaths each year caused by eating less healthy food than people would otherwise.”

The conclusion, if proven out by further studies, is damning: pollinator decline, which has been observed in multiple nations across continents over decades, is already taking a real toll on human health and mortality.

A hungry future?

The escalating tension between a growing human population, which topped eight billion in 2022, the necessity to produce more pollinated foods (75% of humanity’s crops now depend on pollination), and the urgent need to protect pollinators is unlikely to ease any time soon. The latest UN projections suggest the global population could grow to 8.5 billion by 2030, 9.7 billion in 2050, and 10.4 billion in 2100.

Smith warns that as the population continues rising, and lower-income nations become wealthier, demand for pollinated foods will only grow – though that future need was not estimated by the current study.

“These trends have upsides: more diverse diets, less hunger and malnutrition, and higher intakes of health-promoting food groups,” he said. “However, to meet the needs of these larger, wealthier future populations, we will need significant increases in pollinated food production.”

Smith said we either “significantly increase wild pollinators” or double down on intensive conventional farming, which continues to harm our global environment. Those harms include “tremendous emissions of greenhouse gases, pollution of soils and waterways, depletion of finite resources like minerals for fertiliser and freshwater for irrigation, and being the largest driver of biodiversity loss globally,” said Smith.

A moth and a bee pollinating a flower. Fewer pollinators mean less human access to fruit and vegetables. Credit: Schwoaze/Pixabay (Content License)

All of those worsening effects will adversely impact the very pollinators we need. But this is a dilemma with clear remedies, according to Smith. “The solutions to this problem have remarkable consensus in the pollinator ecology community,” he said.

First, we need to protect and create pollinator habitat, including setting aside small forage areas on every farm. We need to also plant the flowers pollinators depend on, and we need to “reduce or eliminate the use of harmful pesticides like neonicotinoids which are known to be extremely harmful to pollinators,” according to Smith.

Such actions wouldn’t just aid pollinators, but insects and biodiversity in general.

“Each of these solutions can be implemented at many scales, from the individual farmer to the national government, enabling immediate action to solve this urgent problem,” added Smith.

Butterflies truly are chaos agents. If their absence can lead to the deaths of hundreds of thousands of people annually, then their abundance – and the abundance of many other pollinating species – could, quite literally, save lives.

This article first appeared on Mongabay.