"Avengers: Endgame" will deal with the aftermath of elimination of half of all life. But what would actually happen to Earth if a real-life Thanos does kill half of all humans?

In the most recent Marvel Cinematic Universe movie "Avengers: Infinity War," the Earth’s mightiest superheroes encountered their biggest challenge yet -- saving life across all the galaxies. However, they failed to stop Thanos, a cosmically powerful villain in the movie, from collecting all the infinity stones. This resulted in the eradication of half of all species in the universe with the snap of a finger.

Thanos thought that the population of the universe previously had had been unsustainable and would eventually put an end to life itself when all the resources were used up. This idea is related to the belief of an 18th-century scholar named Thomas Malthus. His theory predicted the effect of a population growing much faster than their available resources such as food could sustain.

This idea was published in the 1798 essay titled, “An Essay on the Principle of Population.”

Malthus’ theories were not 100 percent correct as humans have succeeded in scaling food resources along with the growth of the population.

At present, scientists have many worries over the effects of population growth compounding environmental problems such as climate change.

Even if the remaining Avengers managed to reverse the devastating action of the Mad Titan Thanos in "Endgame," it still leaves one question: what would be the ecological backlash if such an event actually happens on Earth?

1. Surviving Organisms Will Experience Stomach Ache

Aside from the plants, animals and humans, one of the species that will likely be affected by the snap are microbes. Microorganisms are vital in most of our life processes. They are indigenous living creatures on our skin, gut and other body orifices.

What would happen to our body if we lost half of the microbes needed to function?

“[The microbiome] is a complex ecosystem of organisms that includes bacteria, but also viruses as well as fungi,” Zuri Sullivan, an immunologist at Yale University, said. “Humans have a pretty limited ability to digest complex plant material, so we rely on these commensal bacteria in our microbiome to break down complex carbohydrates that we get from eating plants.”

This microbial ecosystem serves an important role in the digestion of food by breaking down complex molecules.

Also, microbes significantly contribute to our immune system as it teaches our body to identify harmful and harmless bacteria, virus or fungi. They are also directly involved in fighting or preventing deadly pathogens.

“We’re talking about halving, and we’re talking about billions of cells, so going from two billion cells to one billion cells,” Nicholas Lesniak, a microbiologist at the University of Michigan, said. “But then they have a doubling time of hours, so in a matter of hours we’ve already overcome that hit.”

This infers that we might experience a stomachache for a while, but microorganisms have their way of surviving despite of everything that might happen.

2. The decline in insects may affect natural food production and waste management

Farmers will be affected because there will be a limited number of pollinators.

“It would be very chaotic, and I don’t even know how you would snap your fingers in an ecologically sustainable way,” May Berenbaum, an entomologist at the University of Illinois Urbana-Champaign, said. “You would have problems with all the ecosystem services that insects are responsible for, including removing dead bodies or pollination services.”

Insects are important because they are responsible for the process of pollination in plants. The decline of plant pollinators will result in lesser plant crops such as fruits and vegetables.

Some species of insects are also responsible for the speed of decomposition. They feed on decaying bodies and organic materials like feces. If half of their population is wiped out, we will experience a problem with the accumulation of waste.

3. Tiny organisms might dominate Earth

If Thanos would wipe out half of the population of large mammals and other meat-feeding organisms, small animals would likely inherit the Earth. Larger species tend to have a small number of offspring and breed slowly, which would lead to their species eventually dying out completely.

“After a mass extinction, what I’ve found in the past is that it’s the smaller species that tend to breed fast are the source of future diversity,” Lauren Sallan, a paleobiologist who studies mass extinctions at the University of Pennsylvania, said.

This is similar to the Cretaceous–Paleogene extinction event when an asteroid struck Earth 66 million years ago and wiped out the dinosaurs. Some 75 percent of all species were lost, but small, rodent-like mammals managed to survive and adapt.

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