Along the lines of my ‘https://forum.inaturalist.org/t/what-would-happen-if-every-species-of-arthropod-grew-five-times-bigger-overnight/55978’ post, I have this new musing. Let me know what you think.
I would be sad because I would have nothing to photograph… 
But seriously, I would die of boredom and the world would fall apart.
2 Likes
Exactly what I was thinking! I don’t know what I would do with no insects to hunt for. I would probably settle on bird watching, but of course with no insects and arthropods to eat there wouldn’t be many birds to watch.
1 Like
it would be chaos for a while, because whole trophic cascades would collapse. in time, other phylla would take over that roles.
2 Likes
Which others? Birds are gone (swallow population in Switzerland collapsing this year). Pollinators are gone so those crops fail. Detritovores are gone.
1 Like
It would be an absolute, mass-extinction-level, life-ending-as-we-know-it, disaster.
We’d be finished as a species, along with most ecosystems (the only ones that might be unaffected are deep-sea hydrothermal vents and volcanic pools inhabited by extremophiles)
7 Likes
This is a really interesting question, that probably would cause massive changes all over the world, my best guess would be as follows:
Everything that relies on arthropods for food would starve, and then everything that relies on those things as prey, and so on in a wave of extinction up the food web, animals that eat plants, and animals that eat those animals, would live at first, but the carcasses of the billions of now extinct animals would not be scavenged by arthropods, and microbes would take over much of this scavenging, producing a surge in infectious disease that would kill many surviving animals, producing a feedback loop of death.
Zooplankton are largely arthropods, the lose of these and other crustaceans would cause most ocean animals to starve
The rapid accumulation of carcasses scavenged by bacteria, combined with the lack fo arthropods in the soil, would likely alter the chemistry and microbiology of the air, soil, and water, causing additional disruption of ecosystems and yet more death, but I really don’t know if this would be “just a bit extra ecological disruption” or “the atmosphere is now unsurvivable”. I do know that one of the chemicals released would be CO2, contributing to a warmer climate.
With global changes to soil chemistry and microbiology, combined with a loss of arthropods to aerate the soil, many if not most plants are going to die at their roots, a loss of plants and their evapotranspiration will cause inland areas to become drier, and full of dead plants, leading to massive wildfires. If plants die off gradually, fires could consume the dead plants as they die, while killing the live ones and many animals too, like a really bad wildfire season in western North America, but globally until all forests are gone. If the plants die off all at once, entire forests become deserts piled with gigatons of tinder, continent scale fires producing their own weather systems could result, with the flames fanned by category 5+ hurricane winds. Even animals and plants that normally can ride out fires would likely not survive.
Even as the world was being consumed by fire, there are probably some plants, in isolated locations not connected to the burning forests and prairies, that can live without aerated soil and that have not been killed by any of the other disruptions so far, as well as a few animals that eat them. However, these surviving plants would then face climactic changes and reduced sunlight as the smoke from the fires blocked out the sun, cooling the planet, followed by massive warming when the smoke settled out and the CO2 released by most of the global biomass burning or decaying spiked the temperature. Climate and weather patterns would be completely unrecognizable, and this would probably leave any surviving plants and animals in the wrong climate zone, assuming the atmospheric chemistry was even remotely familiar.
I think only microbes would be left once this was over, it would be the biggest mass extinction ever
I am aware that many plants could not reproduce without pollinators and seed disperses, but I don’t imagine that mattering too much since the world ends for other reasons in this scenerio
8 Likes
This! 
2 Likes
And - how close are we? This was 3 years ago.
https://www.theguardian.com/environment/2021/jul/25/the-insect-apocalypse-our-world-will-grind-to-a-halt-without-them
1 Like
The scenario I described involved 100% of arthropods disappearing instantly, I don’t think it is realistic for 100% of arthropods or even insects to disappear, even if populations are declining massively and some species are going extinct.
Also, a lot of the problems I described were caused by species dying off very rapidly. In my scenario the world actually ends due to the accumulation of dead biomass all at once, not simply due to the absence of insects.
I do not mean to say that the insect declines we are seeing are not a major problem, or that catastrophic results from them are impossible, but the scenario I described was really specific to instant total loss of arthropods, and not at all the same as a population decline over years
4 Likes
There would be no more prey for the insectivorous creatures. They would die out. Their predators, with no more food, would die out. The ecosystem would crash.
Also, you spelled ‘disappeared’ incorrectly.
1 Like
Even if a few humans or other animals survived, I wonder how they would be able to sustain themselves.
(removed the extra “s” from “disappeared” in the title)
2 Likes
Thanks.
I don’t think so. I think there are enough other ecological pathways for non-microbial life to still exist after the mass extinction.
I think it would go something like this:
- first mass die-off of animals → All animals who directly or indirectly eat arthropods
- massive increase in population size of non-arthropodal destructors (annelids, mollusks, microorganisms…)
- second mass die-off of animals → All animals who directly or indirectly eat fruit of plants that are pollinated by arthropods
- the decrease of plant populations of plants dependent on arthropods and increase of those who are not (wind pollinators)
I think soil conditions would stay pretty much the same for a few reasons: 1stly animals would probably be the only kingdom experiencing rapid mass die-offs, 2ndly animals make up only a small amount of biomass, 3rdly as mentioned above there are enough other metazoan destructors to take over
⇒ Plants, fungi, and „left-over“ animal destructors would be capable of handling the relatively small amount of new dead biomass and would keep soil conditions stable
⇒ Biomass accumulation would not be nearly as bad as the one that has already happened (the one that caused fossil fuels)
I think self-pollinating plants (blackberries, dandelions, etc., etc.) and wind-pollinating plants (grasses, many trees) would provide enough food for a range of bigger animals.
That being said, I believe, the drastic reduction in biodiversity would weaken the new ecosystems a lot. Diseases will have a far bigger effect, but it’s very unlikely they will actually be enough to finish off all of the non-microbial life that is left.
6 Likes
You pedant!
2 Likes
But also, I thought I heard recently that there’s a functional limit to the size arthropods can reach given their current biology?
1 Like
What do you mean by ‘pedant’?
)