In which country there is no mosquito

Mosquitoes: why don't we eradicate mosquitoes?

A few species of mosquitoes bring endless suffering to mankind. The ecologist Michael Jeffries asks: Shouldn't we get rid of this agony, for good?

Mosquitoes, also known as mosquitoes: blood-sucking, deadly creatures of dawn, more terrible than those vampire demons that used to nest in our nightmares. Mosquitoes don't seem nearly as glamorous as Dracula, but they are, unfortunately, very real. And with the sudden appearance and explosive spread of the Zika virus in Latin America, our old hereditary enemies are once again showing their monstrous side.

Around 3500 mosquito species live on earth - a modest number for an insect family. And among these, it is only a small raiding party of species that harm human health. However, this unit is mobile, powerful, eager to expand and perfectly adapted - the Asian tiger mosquito is one of them, which spreads dengue fever and the chikungunya virus, the malaria mosquitoes of the genus Anopheles or the yellow fever mosquito Aedes aegypti.

The effects on the health of peoples are apocalyptic. Because of the mosquitoes, mankind is still plagued by plagues of biblical proportions: every year up to 500 million new infections with malaria, plus 100 million with dengue fever. And as if that weren't enough of the suffering, mosquitoes are also responsible for the spread of epidemics like West Nile fever. Or just for the Zika infection.

Mosquitoes cause greater loss of life than any other creature on the planet (except ourselves, of course). Which begs the question: what are they actually good for? And, if we could erase them from the face of the earth - should we do that?

The mosquito defenders plead:

Mosquitoes are an important link in the food chain. Especially in the arctic tundras, where hatching mosquitoes appear in huge swarms for a few weeks of summer, they offer migratory birds a rich supply of food. In an article for the magazine "Nature", the author Janet Fang draws attention to another positive effect: the attack by the swarms of mosquitoes diverts the migration of the reindeer, allowing the herds to avoid the pests - which protects the grassland from overgrazing and trampling. Well. So the mosquitoes would be missing in the Arctic. But otherwise? Janet Fang's survey of insect ecologists found that the collateral damage from an extermination would remain manageable.

The survival of very few other animal species is directly linked to that of mosquitoes. Most mosquito eaters would easily switch to other insects. Bats, for example, prefer moths anyway. Except for one species: Vespadelus vulternus, an Australian species - it actually lives in close dependence on a certain mosquito species.

But that's probably the best case that the mosquito defenders can bring up. And the mosquito larvae? Yes, admittedly: They are an important link in some freshwater food chains. Specialists such as the goblin fish ("mosquito fish") live on them. Mosquito larvae also play an important role in the small bodies of water that form in the depressions of living plants under the canopy of the tropical rainforest; for example for the survival of certain poison dart frogs.

The mosquito lawyers have also set up a second line of defense. It is based on the concept of ecosystem service and refers to the role of mosquitoes in pollinating flowering plants (most mosquitoes feed on nectar, only females need a protein-rich blood meal to produce eggs). And the mosquito larvae purify the water in which they live as they feed on organic waste.

Females need a high protein blood meal to produce eggs). And the mosquito larvae purify the water in which they live as they feed on organic waste.

But these arguments do not stand out. The mosquitoes by no means have a monopoly on pollination. They only play a minor role; one that (unlike that of the bee) could easily be deleted and occupied differently. And the larvae? They are also not indispensable as filter feeders in water. Both niches did not remain empty for long after the mosquitoes died out, other organisms would quickly move in, and the ecological wound would heal quickly.

The verdict has been pronounced. But how do you do it?

The mosquito in itself, as we all know, is a fragile creature. However: smacking an individual on the wall is one thing; whole ways of destroying something completely different. A tried and tested strategy: destroy their breeding areas. In the 19th century Europe became - unplanned and almost by the way - malaria-free, because more and more marshes were converted into arable land or developed industrially. Today, however, we regard wetlands as focal points of biodiversity, the destruction of which is forbidden by itself. In addition: some of the worst pathogens among mosquitoes do not need any near-natural water, they also reproduce very successfully in the puddles and pools that arise as waste biotopes in our urban life.

Local populations can be efficiently cleared out with pesticides. DDT was used for this for a long time, and it was quite successful. But it has been shown that the reckless use of DDT not only damages mosquitoes, but also numerous other animal species - and ultimately us humans, as the poison accumulates in our bodies.

Biological control methods have become established. Above all, the already mentioned goblin fish, which eagerly eats mosquito larvae, is artificially settled in many places. Dragonfly larvae also clean up vigorously - but only among regionally narrow mosquito larvae populations.

Doubts remain

In addition, new methods are being tested. Researchers are changing the genetic makeup of male mosquitoes raised in captivity so that they produce offspring that are not viable. If such males are released in large numbers and mate, the entire population collapses.

All of these methods work. But only within limits. Mosquitoes have been training to survive in hostile environments for at least 40 million years. They can make up for terrible losses in no time if just a few populations somewhere get away with it.

There is, as far as I can see, no good reason to defend mosquitoes against plans to eradicate. Their annihilation would remove a curse from humanity. But for this fight we would have to arm ourselves further, perhaps with new weapons from the genetic engineering arsenal.

But doubts remain. Wouldn't the pathogens look for other carriers, fleas or mites for example? Above all: I personally don't like the idea of ​​playing god and exterminating species at all. It is a bitter irony that we humans threaten the existence of many species - just not those that plague us so much.

Michael Jeffries teaches at Northumbria University in Newcastle, England. He is a specialist in the ecology of freshwater ponds.

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