We’ve been told for years that climate change was going to unleash hordes of mosquitoes and disease upon us. For example, this article in Scientific American:
Mosquito-borne Diseases on the Uptick—Thanks to Global Warming
Infection rates of diseases like malaria, dengue fever and West Nile virus are likely to rise as a warming climate creates more mosquito-friendly habitats
Turns out that land use change and the decline of DDT are the biggest factors, while at the same time, climate change has little impact. This goes hand in hand with a study WUWT covered 3 years ago that suggests household size is the biggest factor in malaria, not climate.
From the UNIVERSITY OF CALIFORNIA – SANTA CRUZ
Growing mosquito populations linked to urbanization and DDT’s slow decay
Rising temperatures due to climate change were found to have less influence on mosquito populations than land use changes and the decay of residual DDT in the environment
Mosquito populations have increased as much as ten-fold over the past five decades in New York, New Jersey, and California, according to long-term datasets from mosquito monitoring programs. The number of mosquito species in these areas increased two- to four-fold in the same period.
A new study finds the main drivers of these changes were the gradual waning of DDT concentrations in the environment and increased urbanization. The findings were published December 6 in Nature Communications.
The potential effects of climate change on the spread of insect-borne diseases is a major public health concern, but this study found little evidence that mosquito populations in these areas were responding to changes in temperature or precipitation.
“At first glance, recent increases in mosquito populations appear to be linked to rising temperatures from climate change, but careful analyses of data over the past century show that it’s actually recovery from the effects of DDT,” said corresponding author Marm Kilpatrick, associate professor of ecology and evolutionary biology at UC Santa Cruz.
Kilpatrick explained that the effects of climate change are expected to be seen at the edges of species’ geographic ranges, as species adapted to warm climates move further north and cold-adapted species retreat from the southern parts of their ranges. So a tropical species like Aedes aegypti, which transmits Zika, dengue, and other human diseases, could expand its range northward in the United States as temperatures warm.
“On the cold edge of a species’ distribution, temperature matters a lot. In Washington D.C., for example, where Aedes aegypti is not common now, it might become more common if the winters get milder. Whereas in Florida, urbanization and mosquito control efforts are more likely to be the dominant drivers of mosquito populations,” Kilpatrick said.
Urbanization is an important factor because it changes the species composition in an area, favoring the types of mosquitoes that live near and feed on people, such as Aedes aegypti, and causing other species to decline, such as those adapted to wetlands and other natural habitats.
Mosquito control programs continue to help limit mosquito populations in many areas, but currently available techniques are not nearly as effective as DDT was, Kilpatrick said. “Everyone knew DDT was an extremely effective insecticide, but I was surprised by how long-lasting its effects were. In some areas, it took 30 to 40 years for mosquito populations to recover,” he said.
More than a billion pounds (600 million kilograms) of DDT were used in the United States from the 1940s through the early 1970s. Its use was curtailed in the 1960s and finally banned in the United States in 1972 because of adverse environmental effects, especially on birds and other wildlife, as well as potential human health risks. Yet DDT was still detectable in soil cores as recently as 2000 in New York state, where DDT use was much higher than in New Jersey and California.
In all three regions, both mosquito abundance and the number of species decreased dramatically during the period of DDT use, then steadily increased as the amount of DDT in the environment declined. In New York, the researchers found, patterns of DDT use and its concentration in the environment could explain most of the long-term trends in mosquito populations. In New Jersey and California, however, the analyses showed that urbanization was also an important factor.
Average annual temperatures showed surprisingly little correlation with mosquito population trends. “Precipitation was more important than temperature, but land use was more important than either of those factors,” Kilpatrick said. “The long-term impacts of land use changes on ecosystems are sometimes underappreciated.”
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The coauthors of the paper include Ilia Rochlin and Dominick Ninivaggi at Suffolk County Vector Control in New York; Ary Faraji at the Salt Lake City Mosquito Abatement District; and Christopher Baker at UC Davis.
Since Richard Nixon founded the EPA in 1970 – presumably as a cynical bid to greenwash his tarnished image at the height of the last eco-craze – the organisation has been run by a string of useless placemen and placewomen, who’ve done little that actually helps the environment, but plenty to burden the economy, consumers and business alike with more pointless regulation.
Typical of these was its first Administrator William Ruckelshaus. A lawyer, by training, not a scientist, Ruckelshaus was the man responsible for instituting the America-wide ban on DDT. He did this on no scientific basis whatsoever. In fact, Judge Edmund Sweeney had presided over a seven-month EPA hearing, examining more than 9,000 pages of expert testimony, and concluded:
DDT is not a carcinogenic hazard to man…DDT is not a mutagenic or teratogenic hazard to man…The use of DDT under the regulations involved here do not have a deleterious effect on freshwater fish, estuarine organisms, wild birds or other wildlife.
Ruckelshaus, who had not attended the hearings or read the report, overruled him. Which probably made not much difference in the United States. But the knock-on effects of the near worldwide ban that followed meant that DDT could no longer be used to control mosquito populations, which in turn led to an explosion in malaria, causing the death of millions.
H/T http://www.breitbart.com/environment/2016/12/06/donald-trumps-environmental-protection-agency-chief-could-be-his-best-pick-yet/
“Perry December 7, 2016 at 3:39 am
DDT is not a carcinogenic hazard to man…DDT is not a mutagenic or teratogenic hazard to man…The use of DDT under the regulations involved here do not have a deleterious effect on freshwater fish, estuarine organisms, wild birds or other wildlife.”
Exactly! It’s improper use that is the problem.
Interesting. So DDT is still in the ground, stealthily killing mosquitoes but leaving human beings untouched. Which is not surprising because it never did anything bad to us. None of the readers here remembers the fact that by the end of World War II Europe was full of lice. DDT had been tried out on American troops in Italy and proved itself an effective lousekiller. When the war ended manufacture vof DDT went into high gear. It was used to dust whole populations in Europe, war prisoners, former slave laborers, and DPs in UNRRA refugee camps. I was one such DP dusted by an UNRRA team. For some peculiar reason, this did not give me cancer. As a matter of fact, not one of the millions dusted at war’s end in Europe was reported as having gotten cancer. This fact was well hidden during the DDT hearings when environmentalists implied that DDT causes cancer. Despite lack of proof, that was the final argument that made the ban on DDT official. As a result, millions of children in Africa have died of malaria carried by mosquitoes that would not be there except for the irrational DDT ban. The argument against allowing DDT to be used always hangs on the observation that DDT weakens the eggs of raptors which then do not hatch. An environmental argument that weights birds’ eggs higher than human casualties. The same stupidity that got the whole DDT ban started.
Arno Arrak: “…the observation that DDT weakens the eggs of raptors which then do not hatch….”
Several years before DDT was invented the British Ornithological Order published findings that bird eggs were weakening causing a decrease in population.