Mass seasonal bioflows of high-flying insect migrants.

Gao Hu,Nir Horvitz,Ka S Lim,Nir Sapir,Suzanne J Clark,Jason W Chapman,Don R Reynolds

doi:10.1126/science.aah4379

Abstract

Migrating animals have an impact on ecosystems directly via influxes of predators, prey, and competitors and indirectly by vectoring nutrients, energy, and pathogens. Although linkages between vertebrate movements and ecosystem processes have been established, the effects of mass insect "bioflows" have not been described. We quantified biomass flux over the southern United Kingdom for high-flying (>150 meters) insects and show that ~3.5 trillion insects (3200 tons of biomass) migrate above the region annually. These flows are not randomly directed in insects larger than 10 milligrams, which exploit seasonally beneficial tailwinds. Large seasonal differences in the southward versus northward transfer of biomass occur in some years, although flows were balanced over the 10-year period. Our long-term study reveals a major transport process with implications for ecosystem services, processes, and biogeochemistry.

Highlights

Latitudinal migrations of vast numbers of flying insects, birds and bats [1,2,3,4,5,6,7] lead to huge seasonal exchanges of biomass and nutrients across the Earth’s surface [8,9,10,11]
Mass migrations were consistently towards the north (Rayleigh tests; daytime: medium, 333°; large, 329°; night-time: medium, 349°; large, 349°; Fig. 2A), indicating that migration occurred on winds with a significantly more southerly component than prevailing winds (Watson-Wheeler tests; P < 0.0001 in all cases; table S5)
Seasonally-beneficial migration directions have been previously reported in a few species of large insects, notably pest noctuid moths [3, 14, 18], but our findings demonstrate the ubiquity of such movements among a diverse array of insect migrants for the first time

Summary

Introduction

Latitudinal migrations of vast numbers of flying insects, birds and bats [1,2,3,4,5,6,7] lead to huge seasonal exchanges of biomass and nutrients across the Earth’s surface [8,9,10,11]. Abundance and biomass values for medium (10–70 mg) and large insects (70–500 mg) (referred to collectively as ‘larger insects’) were calculated from measurements of >1.8 million individuals (table S1) detected by Vertical-Looking entomological Radars (VLRs) located in southern UK (Fig. 1A).

Results

Conclusion