Have you heard that 1 in every 3 bites of food depends on pollinators? While this statistic has a questionable origin, the general sentiment is correct— our global food system is dependent on pollinators. Different crops vary in their reliance, but many of our culturally or nutritionally important foods benefit from insect pollination. Because pollinators are important for our food, there is general concern that observed insect declines might cause yield shortages—at least for those crops that are more heavily dependent on insects. Our new study evaluates whether current levels of insect visitation are limiting crop yields worldwide, so that we can better predict how insect decline may affect crop production in the future.

What did we do?

We assessed pollinator limitation (or yield deficits due to insufficient insect visitation) using the most comprehensive, open global dataset on crop pollination to date. The CropPol dataset combines over three decades of pollinator observations and yield measurements from crop fields worldwide. Each of our labs contributed to this project in the past and was involved in recording insects and crop yield in our respective datasets (pictures below).

For this paper, we used 198,360 plant-pollinator interactions and 2,083 yield measurements to measure pollinator limitation in 120 datasets. Our data represents 32 crop species or roughly a third of the leading global crop commodities that are pollinator-dependent. Crop fields are spread worldwide across Europe (n=701), North America (n=361), Asia (n=206), South America (n=201), Oceania (n=34), and Africa (n=33).

How prevalent are current yield deficits due to lack of pollinators worldwide?

We discovered that insufficient pollinator visitation limited the crop yield of 28-61% of our datasets, across 25 different crop species. This is a substantial reduction in global agricultural productivity (although less than previously reported). In our study, blueberry, coffee, and apple crops were most frequently affected by pollinator limitation, and yield deficits were found in 85% of the countries that we evaluated. 

Are there risk factors that predict where pollinator limitation is more likely?

Next, we wanted to identify if there were hot spots where pollinator limitation might occur more frequently, so that we could prioritize future interventions by location, specific crop species, or growing practices. We were surprised to find, however, that most factors we tested were insignificant. Pollinator limitation was widespread, but it was not associated with 1) pesticide management, 2) geographic region where a farm was located, 3) climate, 4) crop species or family, 5) crop growth form (e.g., tree versus shrub), 6) bloom phenology, or 7) or a crop’s expected reliance on pollinators.

The only pattern we identified was for a minority of the datasets (15%), the probability of pollinator limitation decreased with increasing forested landcover surrounding a crop field at a 1km radius. This is consistent with previous studies finding that forests can support crop pollinators.

By how much could increases in pollinator visitation improve crop yields?

Finally, after observing that pollinator limitation is a widespread issue, our natural follow up was to ask, how much effort would it take to improve crop yields in affected fields? Despite the prevalence of pollinator limitation, our analysis came to the optimistic conclusion that relatively small increases in pollinator visitation could address much of the observed yield shortfalls.

We found that, on average across 33 of our pollinator limited datasets, crop deficits could be reduced by roughly 2/3 if low-visitation fields were visited by the same number of pollinators as the high-visitation fields within the same dataset. Because we directly measured insect visitation to crop flowers and subsequent yield in all crop fields, our recommendations are rooted in realistic field conditions. In absolute terms, the number of insects needed to reduce yield deficits can be quite small too. For example, for a subset of 8 crop systems that recorded pollinators observed per 100 flowers per hour, raising average visitation rates from 4 to 37 insects per hour would close observed yield gaps.

Why does this matter?

We believe that our main findings are both cause for concern and optimism. We did detect widespread yield deficits which suggests that future pollinator decline may exacerbate the effects of current pollinator limitation. However, we also estimate that current yield deficits could be reduced with realistic increases in pollinator visitation across individual crop fields. This suggests that with continued investment in pollinator management and research, we can improve the efficiency of our existing crop fields to meet the nutritional needs of our global population.

References

[1] Berenbaum, M. Reality bites. Am. Entomol. 64, 134–137 (2018).

[2] Klein, A. M. et al. Importance of pollinators in changing landscapes for world crops. Proc. R. Soc. B Biol. Sci. 274, 303–313 (2007).

[3] Potts, S. G. et al. Global pollinator declines: Trends, impacts and drivers. Trends Ecol. Evol. 25, 345–353 (2010).

[4] Allen‐Perkins, A. et al. CropPol: A dynamic, open and global database on crop pollination. Ecology 103, e3614 (2022).

[5] Sáez, A. et al. Managed honeybees decrease pollination limitation in self-compatible but not in self-incompatible crops. Proc. R. Soc. B Biol. Sci. 289, (2022).

[6] Ricketts, T. H., Daily, G. C., Ehrlich, P. R. & Michener, C. D. Economic value of tropical forest to coffee production. Proc. Natl. Acad. Sci. U. S. A. 101, 12579–12582 (2004).

Poster image Andrena carolina (C) Max McCarthy, PhD Student Winfree Laboratory