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Is there any scientific definition or evidence of such a thing as the mosquito line?

My first apartment in Manhattan was on the 25th floor of the Park Row building in the Financial District. The broker assured me I could keep the windows open because we were "above the mosquito line."

This was untrue, and mosquitos would regularly enter the apartment if the window was left open.

I later found out that many New Yorkers believed that they lived above or below "the mosquito line", and a search of Google reveals several casual mentions of a delineation above which there are no mosquitos.

I found a mention of "the mosquito line" in the transcript of the 2006 documentary An Inconvenient Truth where Al Gore states definitively:

"There are cities that were founded because they were just above the mosquito line. Nairobi is one. Harare is another. There are plenty of others. Now the mosquitoes with warming are climbing to higher altitudes."

Bjørn Lomborg, author of The Skeptical Environmentalist and critic of An Inconvenient Truth dedicates a fact checking page to Al Gore's mention of a "mosquito line" where he states that he had found no official definition for the term:

There seems to exist no official definition of what is meant by a "mosquito line". You might compare with the term "tree line", which is a line above which no trees can grow. By analogy, you would assume that a "mosquito line" is a line above which no mosquitoes can live. But this interpretation would not fit in relation to malaria in Kenya. Instead, you would have to understand the term as a line above which malaria is not present every year, but only in certain years, when epidemics occur.

Lomberg then proposes a definition of the term as it relates to climate, and seems to give Al Gore the benefit of the doubt:

Nairobi is situated at 1660 m and thus may be said to be just above the line delimitating the zones of regular occurrence. The coldest month, July, has average maximum temperatures of 20.6° C, i.e. temperatures less than optimal for the P. falciparum parasite. Thus, it is true that Nairobi is just inside the zone where malaria occurs only as epidemics, not as a permanent or seasonal penomenon. If this is what is understood by "the mosquito line", Al Gore is approximately right.

There are no doubt altitudes above which mosquitos or any living thing would not survive - and there are climates in which mosquitos do not thrive.

Presumably New York apartment brokers and their customers imagine the "mosquito line" as a limitation on how high a mosquito can fly - because New York City is at sea level.

But is there anything in the literature that would suggest that there is, in fact, a "mosquito line"?

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Are you asking about a geographical altitude or a city altitude? Almost certainly unrelated. –  DJClayworth Aug 22 '12 at 3:35
    
There have been comments by many seeking to climb on the bandwagon of worry about climate change alleging that malaria will spread in a warmer world as mosquitos spread. But malaria was endemic in cold northern european countries in the early 20th century and didn't disappear because the world got colder. There may be a mosquito line but it it isn't relevant to the damage climate change could cause. –  matt_black Aug 22 '12 at 23:23
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2 Answers

Scholarly papers which mention the (geographical) mosquito line include:

In the Hawaiian islands, the surviving species of the great Hawaiian Honeycreeper evolutionary radiation survive only above a certain altitude – the ‘mosquito line’ – above which the introduced mosquito that transmits an introduced bird malaria (fatal to honeycreepers) does not survive. That line will move upslope in a warming world so the mosquito- and malaria-free zone will shrink

Most honeycreepers, especially endangered species, now persist only in forests above 1500 m elevation, where cool temperatures prevent effective malaria development in mosquitoes.

Climate change (global warming) appears to be moving the altitude limits of malaria to higher elevations, for example in the East African highlands and Madagascar.

An important factor influencing the prevalence of the species in particular localities and even in the major features of the world distribution is altitude.

and many more. I recommend this Google search for a bigger list.

It seems that temperature is a factor, so there is no single worldwide altitude above which mosquitos cannot live - it varies from place to place. It is clear that the mosquito line altitude is measured in the thousands of feet - the height of a New York apartment building is not going to make a difference.

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Could you please add a brief summary? Do they support the idea? –  Oddthinking Aug 22 '12 at 4:45
    
Yes, the papers on Hawai'i support the premise that mosquito populations diminish and then stop above certain altitudes, which on the Big Island represent climate zones (remember, Mauna Kea and Mauna Loa regularly have snowfall on days when the beach is 80F). A caveat though is that these are variations in the thousands, not hundreds of feet, and any given altitude in Hawai'i has a quite-stable characteristic temp. I live at 1700' on the Big Island and we have mosquitoes. You have to go above, say, ~5000' to see the malaria-vulnerable native species. –  Larry OBrien Aug 22 '12 at 18:53
    
Your Google Scholar search turned up 19 hits for "mosquito line" altitude not all of which refer to this. Leave out altitude and you get five times as many, the majority of which use "mosquito line" to mean a set of mosquitoes bred for particular experimental purposes. –  Henry Aug 22 '12 at 20:14
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Mosquitoes, like other animals, have ranges and if you draw a line around these ranges you have a "mosquito line". The US Centers for Disease Control and Prevention have a map of the ranges of the 30-40 species from the genus Anopheles which can carry malaria. A map of all 3500 mosquito species would cover a wider area.

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It is possible to distinguish the highest mountains here, such as the Himalayas/Tibet in central Asia and the Rockies/Andes near the west coast of the Americas, and there are some small mosquito free areas in East Africa. But areas of desert are as obvious, showing the importance of water for mosquitoes. Many of the areas shown are now malaria-free due to 20th century malaria eradication efforts even where mosquitoes remain: Finland is an example of a relatively cold area which had several malaria epidemics in the 19th century reaching to the Arctic circle, and which returned to soldiers in 1941.

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