Large swarms of insects can generate as much electrical charge in the air as thunderstorms
A new study has found that large swarms of insects, like honeybees, can generate enough electrical charge in the air, similar to those seen during thunderstorms. This is surprising and could have some exciting implications for our understanding of how animals can affect the atmosphere.
You can view the study in the journal iScience.
The study's results may show that localized patterns in the atmosphere's electric field should be modeled with biological processes.
But how is this possible?
According to the study, the flapping of many tiny wings in a swarm of insects can disturb electrical charges in a column of air enough to change the electric field of the air in a local area in a big way. As insects' wings flap, they can shake off electrons from dust, moisture, and insect parts in a body of air.
By doing this, negatively charged electrons can be jarred loose, creating an electrical potential gradient that can be measured.
Storms typically generate this kind of gradient too, when small ice particles ascend in air columns and collide with larger fragments falling to the ground. This creates a kind of "conveyer belt" of charges that amplify potential gradients between the tops of the clouds, the bottoms of the clouds, and the ground below.
The resultant charge buildup can't be seen directly, but the outcome is known to anyone whose experienced a thunderstorm - lightning.
At some point, this reaches a point of no return, and ionized channels form. This causes a lightning bolt to be made to even out the charge. Even if there isn't any lightning, areas with opposite charges can affect the flow of ions, such as different contaminants and dust particles.
Many things can affect potential gradients, such as how clouds move, how much rain falls, and even cosmic ray showers. Still, until recently, no one had even considered that lifeforms could create something similar.
"We always looked at how physics influenced biology, but at some point, we realized that biology might also be influencing physics," explained the study's lead author, Ellard Hunting, a biologist at the University of Bristol in the UK.
"We're interested in how different organisms use the static electric fields that are virtually everywhere in the environment," he added.
Insect swarm's environmental effects may be more significant than we first thought.
This builds on other studies that are building up a body of evidence that insects and other invertebrates can carry charges that give them a tiny potential difference compared to their surroundings. Some people have even thought that baby spiders can use this effect to get into the air.
However, the mass effect of this from swarms has never been studied. To this end, the researchers decided to see what they could find by studying a honeybee swarm at the University of Bristol School of Veterinary Sciences field station.
The researchers followed the local potential gradient of a moving swarm by using an electric field sensor and a camera to measure the density of the bees. The insects flew over for three minutes, increasing the potential gradient above by up to 100 volts per meter.
By doing this, the researchers were able to anticipate with some degree of confidence how the charge in the environment may change if a certain number of bees buzzed over a specific area of air.
A further investigation proved the voltage was connected to the swarm's concentration.
The research team used the same reasoning to explain why their estimations held up to testing for bees and other swarming insects. They also determined that a significant locust swarm could produce charge densities resembling those found in electrical storms by scaling up the individual charges for locusts to plague-sized levels.
"Interdisciplinarity is valuable here – electric charge can seem like it lives solely in physics, but it is important to know how aware the whole natural world is of electricity in the atmosphere," explained Giles Harrison, an atmospheric physicist from the University of Reading.
"The atmosphere hosts multiple sources of electric charge that influence critical processes such as the aggregation of droplets and the removal of dust and aerosols. This is evident in the variability of the atmospheric electric field. Whereas these electric fields are known to respond to physical and geological processes, the effect of biotic sources of charge has not hitherto been considered. Here, we combine theoretical and empirical evidence to demonstrate that honeybee swarms directly contribute to atmospheric electricity, in proportion to the swarm density. We provide a quantitative assessment of this finding, by comparing the electrical contribution of various swarming insect species with common abiotic sources of charge. This reveals that the charge contribution of some insect swarms will be comparable with that of meteorologically induced variations. The observed transport of charge by insects therefore demonstrates an unexplored role of biogenic space charge for physical and ecological processes in the atmosphere."
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