Why pollinating insects are dwindling, and how it will impact crops

A pollinator decline is putting several tropical crops at risk. (Photo: Bhaskar via Wikimedia Commons)

Twenty-five years ago, a single bee colony in the Hanumangarh district of Rajasthan produced 50 to 60 kg of honey during the mustard growing season (October to March). “Today, that number has dwindled to a mere 15 kg,” says Rakesh Sharma, a beekeeper in the region.

The problem is not unique to Hanumangarh. The decline in honey production, and bee populations, in recent years has raised concerns among apiarists and farmers from Rajasthan, Uttar Pradesh, Madhya Pradesh and Haryana. However, a large portion of the evidence is mostly based on local accounts or regional studies. For example, a 2022 study in Bengaluru found a 20 percent decrease in bee abundance, while another study found giant honeybees to be endangered in India.

Now, a new global study, published this month in Science Advances, has declared that a pollinator decline could put several tropical crops at risk. Led by researchers from the University College London and the Natural History Museum, it found that the projected risk to crop production in 2050 from insect pollinator abundance losses will be highest in the tropical regions of sub-Saharan Africa, South America, and Southeast Asia.

In terms of total production, China, India, Indonesia, Brazil, and the Philippines emerge as being most at risk. Among crops, cocoa is estimated to be at highest risk, by a large margin, especially in Africa, followed by mango (particularly in India) and watermelon (in China).

Cause for concern
“Pollinators visit flowers to feed on nectar and pollen, and they may accidentally deposit pollen from one flower to another. The plant uses the pollen to produce a fruit or seed," says Jharna Shah, an independent researcher studying the impact of climate change on bees in Rajasthan.

While a decline in pollinator numbers might not seem significant at first glance, the impact on biodiversity and food production would be considerable. Around 75 percent of the world’s flowering plants and about 35 percent of its food crops depend on animal pollinators to reproduce, according to the United States Department of Agriculture.

In India, for example, a 2022 study found that moths are vital to pollination in the Himalayan ecosystem of northeast India, identifying them as potential pollinators of 21 plant families in Sikkim and Arunachal Pradesh. The study found that 65 percent of the moths studied (91 species) carried sufficient quantities of pollen grains to be considered as potential pollinators.

The findings on diurnal pollinators are equally eye-opening. A decline of bees alone could lead to a potential agricultural crisis in India, as crops in 50 million hectares across the country depend on them for pollination. Recent research already suggests that declining bee populations are reducing crop yields, which is impacting the availability and cost of nutritious foods, such as fruits, vegetables, legumes, and nuts. “This could increase income and food insecurity for vulnerable sections, especially small-scale farmers in India,” says Shah.

Known factors
Various reasons have been cited for this decline. Changes in the world climate and land use have reduced the number of pollinating insects for key tropical crops, according to the global study. It noted that bees, flies, moths and other pollinators are more affected by these changes than the general insect population. In fact, pollinating insects dropped by 61 percent during periods of abnormally high temperatures and reduced supply of flowering plants. The other key factors cited for the decline are habitat destruction, improper land use (such as grazing), fertilisers and crop monoculture farming, and high pesticide use.

Closer home, habitat change is a major factor in the decline of pollinators. According to Global Forest Watch, India lost 3,71,000 hectares of primary forest cover and 2.07 million hectares of tree cover between 2002 and 2021. Rapid urbanisation, agricultural expansion, and deforestation have destroyed and fragmented critical pollinator habitats.

The government's push for genetically modified (GM) crops and the Green Revolution has also incentivised monoculture, which simplifies biodiversity and reduces the number of pollinators and insects that naturally control agricultural pests. Monocultures also create environments where pests thrive, leading to a further decline in pollinators from diseases caused by these pests.

Agricultural intensification via monoculture farming has additionally increased dependence on synthetic agrochemicals like pesticides and fertilisers. “Bees, for example, do not visit the flowers of crops sprayed with pesticides. It can have a ripple effect over time over the entire food system,” says Sharma.

A 2011 study in India was the first assessment of pollinator-dependent vegetable production in any country. Using 45 years of data from the Food and Agricultural Organization, it found that while the area under pollinator-dependent crops increased until 1999, it declined thereafter. The relative yield growth rate of pollinator-dependent crops also slowed after 1993, suggesting pollinator limitation.

In addition, environmental pollution, including sewage, landfill leachates, air pollution, and industrial chemicals, is a significant contributor to the decline of insect pollinators. “Cumulatively, this again highlights the urgent need for global action to mitigate climate change, slow down land use changes, and protect natural habitats. Only then can the decline in pollinating insects be stopped, or even reversed,” says Shah.