Diversity matters: effects of density compensation in pollination service during rainfall shift

1. Extreme weather events are increasing in frequency due to the warming climate. Such extremities can jeopardise ecosystem services and create economic imbalances. Tropical developing countries are predicted to suffer the maximum consequences of such events.
2. We examined the impact of such an event – extreme rainfall fluctuation - on a critical ecosystem service – pollination, which can be intricately linked to a country’s economy. We performed this study in a dominant peri-urban vegetable hub of an agriculture-dependent developing country.
3. We found that the yield of all pollinator-dependent crops grown across a large spatial scale (district) over multiple years (six) drastically declined with the decrease in rainfall.
4. At the local scale, we found that the dominant crop (representative horticultural crop) had a significant drop in yield during drought, likely due to the production of fewer female flowers and a significant shift in the pollinator community.
5. We found that Trigona sp. (one of the four pollinators) was the critical pollinator positively influencing fruit to flower ratio (FFR) (an indicator of pollination service) in the normal rainfall year. However, despite its sharp decline during drought, the FFR remained unaffected. We found that during drought, Apis dorsata was crucial in maintaining FFR and compensated for the decline of the critical pollinator across 67% farmlands.
6. Our study demonstrates the role of ecosystem stabilising mechanism rescuing the crucial ecosystem service during climatic variability over the temporal scale.