If mosquitoes were to become extinct, would the ecosystem collapse?

Every day, Jitwadi Murphy opens a stuffy padlocked room at Walter Reed Army Institute of Research in Silver Spring, Maryland, to a swarm of malarial mosquitoes. She grinds up fish food and feeds it to millions of tsetse, then delivers unconscious mice for the many "pregnant mosquitoes" to suck blood from their abdomens - they suck 24 of these rodents dry each month. Murphy has studied mosquitoes for 20 years and has worked to limit the spread of parasitic organisms carried by mosquitoes. That said, Murphy says she'd still rather wipe mosquitoes out of the world altogether.

This view is shared by many. About 247 million people worldwide are infected with malaria each year, and nearly a million of them die as a result. Mosquitoes also transmit yellow fever, dengue fever, BSE, Rift Valley fever, chikungunya, and West Nile virus, creating an even greater medical and financial burden. Then there is the infestation: they form dense swarms of mosquitoes that can even suffocate caribou herds in Alaska. And now the mosquito population is at a seasonal peak, with the entire northern hemisphere filled with their stinging, sucking mouthparts coned into human flesh.

What would happen if there were no mosquitoes in this world? Would anyone or anything else miss them? Nature asked some experts in mosquito biology and ecology about this, and got some unexpected answers.

Currently, there are more than 3,500 named species of mosquitoes, only a couple of hundred of which will bite humans or buzz around you. They thrive in every habitat on nearly every continent and play an important role in a wide range of ecosystems. "Mosquitoes have been on the planet for hundreds of millions of years," Murphy says, "and they've evolved in concert with multiple species along the way." Eliminating one type of mosquito could leave a predator without food, or a plant without a pollinator. And exploring a world without mosquitoes isn't just an exercise for your imagination: a great deal of effort has been invested in developing a viable way to wipe this pernicious disease-spreading species off the face of the earth.

However, scientists also acknowledge that, in most cases, the ecological niche vacated with the disappearance of mosquitoes is filled by other organisms, and the ecological trauma caused by their eradication is quickly recovered. Life will go on, as it always has - and maybe even better. Especially for those few mosquito species that are major disease vectors, "It's hard to say that there's any harm in eradicating them; at best, there might be some misadventure in the eradication process." So says Steven Giuliano, an insect ecologist at Illinois State University in Normal. Medical entomologist Carolus Brisola Marcondes of the Federal University of Santa Catarina in Brazil echoed this sentiment, saying that she believes a world without mosquitoes is "much safer for us, and that eradicating Anopheles mosquitoes would mean a lot to humans."

Arctic mosquito swarms

The biggest ecological changes that could result from mosquito eradication could occur in the Arctic tundra, which is home to mosquitoes including Aedes pinchers and Aedes aegypti. Eggs hatch after the next year's snow melt and then take only 3-4 weeks to develop into adults. From northern Canada to Russia, these mosquitoes can explode in numbers for a short period, even forming thick clouds in some areas. "It's really rare in the world, and I'm afraid there's nowhere else in the world where such a large amount of biomass would gather." Daniel Stickman said. He is an entomologist who now works as the director of the USDA's Medical and Urban Entomology Program in Beltsville, Maryland.

Scientists have differing opinions about the consequences of wiping out these creatures. Bruce Harrison, an entomologist with the North Carolina Department of Environment and Natural Resources, estimates that without mosquitoes as food, the number of migratory birds nesting in the tundra could drop by more than 50 percent. But some researchers disagree. Kathy Kirby, a wildlife biologist who works for the U.S. Fish and Wildlife Service in Fairbanks, Alaska, said Arctic mosquitoes did not show high numbers in bird stomach contents samples, and that midges are a more dominant food source. "People may be overestimating the number of Arctic mosquitoes, given that mosquitoes like to congregate around us," she said.

Mosquitoes suck up to 300 milliliters of blood from each caribou every day. Reindeer herds are thus thought to deliberately choose windward travel routes to escape the mosquitoes. And small changes in travel routes can have a big impact on the Aortic valley, given that thousands of caribou migrate through this route, trampling the ground, eating lichen, transporting nutrients, plus feeding wolves, which in turn often changes the ecology along the way. All things considered, mosquitoes should be missed in the Arctic - but does this hold true elsewhere?

Fin-tipped delicacies

Richard Merritt, an aquatic entomologist at Michigan State University, says: "Mosquitoes are a delicacy, and they're easy to catch." If mosquito larval tsetse were to disappear from the world, hundreds of species of fish would have to change their recipes to survive. Harrison says, "It sounds easy, but traits like feeding behavior are genetically embedded in these fish." The mosquito-eating fish, for example, is specialized in feeding - as a mosquito killer, it is often kept in rice paddies or swimming pools to control pests that might go extinct without mosquitoes. And the extinction of mosquito-eating fish or other fish pairs may have a significant impact on the food chain upstream and downstream.

Many species of insects, spiders, salamanders, lizards, and frogs would also lose a major food source, and in a study published in 2010, researchers documented the survival of hairy-footed swallows in France's Camargue Wetland Nature Park after being sprayed with a microbial mosquito control agent. They found that an average of two chicks hatched per nest after the spraying, compared to an average of three chicks at a control site without the agent treatment.

But most of the birds that feed on mosquitoes are likely to switch to other insects that have proliferated and taken over their ecological niche in the "post-mosquito era. As for other insectivores, they probably won't miss mosquitoes at all: moths are the staple food of bats, and mosquitoes make up less than 2 percent of their digestive tract contents. Janet McAllister, a medical entomologist at the CDC in Fort Collins, Colorado, offers an analogy: "If you were going to consume a lot of energy, would you eat 22 ounces of moth fillet or 6 ounces of mosquito burger?"

With so much more on the menu, it seems that in a mosquito-free world, most insect-eating species wouldn't have to starve. The evidence of mosquito extermination causing ecosystem damage is not strong enough to make "exterminators" think twice.

Happy to serve

As tsetse when it comes to mosquitoes, they constitute a significant amount of biomass in aquatic ecosystems worldwide. From seasonal pools of standing water to tree holes to standing water in old tires, tsetse live in large numbers in a wide variety of water bodies. In flood plains, the density of tsetse is so high that even the surface of the water ripples with their wriggling. The tsetse feed on decaying leaves, organic debris, and microorganisms. The question is whether other filter feeders will top up if there are no mosquitoes. "There are quite a few creatures that address debris and decaying matter, and mosquitoes are neither the only ones nor are they considered vital." Giuliano said: "If you remove just one rivet from the wing, it's unlikely that the plane will fall off."

If mosquitoes were to go extinct, would the ecosystem collapse?

Mosquito larvae, tsetse

The effect of mosquito disappearance may depend on which specific body of water is being discussed. The "bottle" of purple bottlebrush on the east coast of North America usually contains a mini-pond with a volume of 25 - 100 ml, and tsetse are important members of this small, tight-knit community. The only insects that live there are the North American bottlebrush mosquito and the bottlebrush shaker mosquito, with cohabitants being tiny organisms such as rotifers, bacteria, and protozoa. While other insects drown in the water, the shaker mosquito chews up their carcasses and the bottlebrush tsetse feeds on the residue while providing nutrients such as nitrogen to the plant. In this case, eliminating the mosquitoes would potentially affect the growth of the plants.

John Addicott, an ecologist now at the University of Calgary in Alberta, Canada, published a study in 1974 on the predator-prey structure within the pigweed. The results showed that the diversity of protozoa was higher when tsetse was present. It was proposed that tsetse predation simultaneously controls the number of dominant species in the protozoa and therefore allows other species to survive. And the broader implications of this for plants are not well understood.

If mosquitoes do provide "ecosystem services" (i.e., human benefits from nature), this would provide a stronger argument for their retention. Dina Fonseca, an evolutionary ecologist at Rutgers University in New Brunswick, N.J., explains this by using an analogy with several small bugs in the midge family that bites people, or "midge mosquitoes," as they are usually called: "Those who are bitten by midges or who have been infected by viruses, protozoa, and filarial worms through their bites, will be very willing to exterminate these little bugs." But given that several species of midges are pollinators of tropical crops such as cocoa trees, "exterminating them could create a world without chocolate."

Adult mosquitoes rely on nectar for the energy they need to survive (only some species of female mosquitoes have to rely on occasional blood-sucking to take in the protein needed to lay eggs), and without them, thousands of plant species would lose a class of pollinators. However, McAllister said the pollination role of mosquitoes is not critical to the survival of human crops. If mosquitoes were any good, humans would have tried to take advantage of them," she said. If you have to get something from the mosquitoes, then they have to disappear."

In the end, it seems that there are few things that mosquitoes can do that other creatures can't - with perhaps one exception: they are deadly efficient at sucking blood from one animal and then sticking their mouthparts into another: and this provides an ideal way for pathogenic microbes to spread.

Stickman says: "The ecological effect of mosquito pest eradication is that the population will increase. That's the result." Eliminating mosquitoes will save many lives and save many more people from disease. Many countries will no longer be afflicted with malaria. The World Health Organization estimates that in sub-Saharan African countries, the disease costs 1.3 percent of the gross domestic product each year; without mosquitoes, that money could be saved for accelerated development. "The financial burden on health systems and hospitals would be reduced, public health spending for insect-borne disease prevention and control could be invested in other priority health issues, and school dropout rates would be lower." So says Jeffrey Hill, a WHO malariologist in Manila.

Phil Ronnibos is an ecologist now working at the Florida Medical Entomology Laboratory in Vero Beach. He believes that "eradicating mosquitoes will only temporarily alleviate human suffering. His research shows that trying to eradicate a particular disease carrier is mostly futile, given that its ecological niche is quickly populated by other carrier organisms. His team collected female yellow fever mosquitoes from dump sites in Florida and then found that some of them were inseminated by Asian tiger mosquitoes, which carry the causative agent or pathogens of many human diseases. Such insemination sterilizes female yellow fever mosquitoes - demonstrating a way for insects to replace other species.

So while many beneficial species, from tuna to coral, have been inadvertently pushed to the brink of extinction by humans one after another; a tiny bug with almost no redeeming qualities has been allowed to survive without being endangered by a thousand human efforts. "The ecological niche that mosquitoes occupy in the environment is not infallible," says Joey Conlon, an entomologist with the American Mosquito Control Association in Jacksonville, Florida, "and even if we succeed in eradicating them in the future, those ecosystems where they are active will probably just have a little hiccup and go on with whatever they do. The gap left by the mosquitoes will be taken over by others, but whether the successor will be better or worse ...... no one knows."