Fijian sweat bees thrive amid habitat change, defying global pollinator decline

The story of pollinator collapse has become familiar enough to feel inevitable. Habitat loss, climate disruption, invasive species—the cascade of human-driven pressures that squeeze out native insects across the globe. But in Fiji, researchers have found something that breaks the expected pattern. A long-term study of the island nation's lowland sweat bees reveals populations that are not retreating but expanding, thriving in the very landscape transformations that have devastated pollinators elsewhere.

The work, led by Flinders University and published in the Journal of Biogeography, tracked native bee populations across Fiji's main island, Viti Levu. What Patricia Slattery and her colleagues discovered challenged the prevailing narrative. The lowland sweat bees they sampled—species belonging to the genus Lasioglossum—have undergone recent population expansions independent of broader climate trends affecting the Pacific region. These ground-nesting insects have not merely survived the reshaping of their world; they have multiplied within it.

The mechanism behind this resilience lies in how these bees have learned to read the landscape. When humans cleared forests and introduced exotic flowering plants to Fiji over the past three millennia, they inadvertently created new niches. The open ground exposed by deforestation became nesting habitat. The invasive plants provided food sources. For species already adapted to lower elevations and less specialized in their ecological requirements, these changes opened doors rather than closing them. The contrast with other native insects is stark. Some ant species and forest-specialist bees have declined as biodiversity has contracted. The lowland sweat bees, by contrast, have capitalized on anthropogenic disturbance in ways their more specialized cousins could not.

The geographic pattern within Fiji itself tells part of the story. Highland species on Viti Levu have held relatively steady in number, their populations stable but not surging. The lowland populations, by contrast, show a strong recent upward trajectory. This divergence suggests that elevation and habitat specialization matter profoundly. The bees that depend on intact forest have struggled. The bees that can nest in open ground and forage on a broader palette of plants have flourished.

Co-author Mike Schwarz notes that the life history of these lowland species—their behavioral and physiological flexibility—has allowed them to adapt in ways that forest specialists simply cannot match. The genetic signatures of this adaptation reach back into deep time, bearing the mark of human arrival in Fiji roughly three thousand years ago. The bees have been shaped by human presence for millennia, and that long coevolution may have primed them for the accelerated changes of recent centuries.

Yet researchers are careful not to overstate what this finding means. The Fijian sweat bees represent an exception, not a rule. Across the globe, native pollinators face major losses as environmental disruption accelerates. Mountain-dwelling tropical insects, in particular, rank among the most vulnerable animals on Earth, with documented declines in many regions. The fact that some lowland tropical insects can benefit from human-mediated environmental change does not erase the broader crisis. It simply reveals that the relationship between humans and nature is more textured than any single narrative can capture. Some species lose everything. Others find unexpected opportunity in the ruins of what was. Understanding which is which, and why, may be essential to navigating the ecological transformations already underway.