Via the SPPI Blog – Trying to Hit a Mosquito with a Sledgehammer
Source: World Climate Report
One of the standard tenets of the global warming bible is that malaria will get worse as temperatures rise. We’ve addressed this many times before, primarily by noting that the link between high temperatures and high malaria infection rates is anything but straightforward. Infectious disease expert Paul Reiter is quick to point out that malaria has been observed inside the Arctic Circle…and this is obviously not typical of a so-called “tropical” disease.
Nevertheless, the case for a malaria-temperature relationship stands on reasonably solid ground. Mosquitoes are more active at higher temperatures so they can expand their range. Biting frequency also depends on temperature, to some extent, so this should increase the infection rate, assuming the little buggers can find enough people to bite. Fairly sophisticated models have been developed that estimate the impact of weather variables on malaria infection rates. On the face of it, this seems like a reasonably solid argument.
But in a recent paper in Nature, Oxford University’s Peter Gething and colleagues from Oxford and the University of Florida took a careful look at global malaria data to see if the predicted trend was correct.
They uncovered data from around the year 1900 showing where malaria was observed. These data not only show where malaria occurred, but also different categories of endemicity (in locations where the disease is continually present, the categories depict the approximate percentage of mosquitoes that carry the malaria parasite). 1900 is a key time because of the lack of prior malaria intervention efforts. The authors then used a current model of the parasite’s transmission to create a map at the same scale for the year 2007. The 1900 and 2007 maps are shown in Figure 1a and 1b, respectively. It’s then a simple matter to subtract the two maps to show how malaria endemicity has changed over the last 100 plus years (in this case, this is a subtraction of categories). This is shown in the bottom Figure (1c), where red shows increasing malaria and blue decreasing malaria.
There is virtually no red on the map.
Figure 1. Malaria endemicity in 1900 (a, top) and 2007 (b, middle) by increasing severity category. The difference in endemicity (c, bottom) from 1900 to 2007 indicates worsening malaria in red areas and improvements in blue (Gething et al., 2010).
If you give this issue a moment of thought, this result should be obvious. Of course malaria is not as bad now as it was 100 years ago. Global health interventions should have reduced the problem significantly.
But it has also been warming since 1900, including nearly all of the regions were malaria was endemic. Look at the problem this way: if you had available to you a) the current malaria/climate models, b) the 1900 malaria map, and c) a fairly accurate prediction of future temperatures, there is no possible way you would have predicted anything close to the map shown in Figure 1b for 2007. That’s because the climate models do not consider factors other than climate (this is also why heat-related mortality/climate model projections don’t work either).
It’s fair to say that everyone who works on this issue is pleased that malaria is less of a problem now. This speaks to the importance of intervention and awareness programs in fighting transmission. And the trend really shouldn’t be that surprising. But one might argue that regardless of the Gething et al. result, this does not mean that climate is not important.
The key part of the Nature paper, however, is the author’s attempt to quantify the effect of climate compared to other factors. To estimate these, they calculated something called the “basic reproductive number” of the malaria parasite (this is a measure of how efficiently the disease spreads within a population that has no inherent resistance to it). Even though the exact reproductive number is hard to predict, you can estimate the magnitude of the changes (also called the “effect size”) that might arise from different factors, such as climate or intervention programs.
Climate projections vary, of course, depending on the models and assumptions used, but the maximum effect sizes for the year 2050 arising from climate changes are around 2 or 3 (a doubling or trebling of the reproductive number). By comparison, the observed changes in effect size (between 1900 and 2007) were much greater than the projected climate change impact. More specifically, Gething et al.
…found that, of the 66 million km2 of the Earth’s surface thought to have sustained stable/endemic malaria in 1900, 12%, 18% and 57% had exhibited proportional decreases in the reproductive number of up to one, between one and two, and greater than two orders of magnitude, respectively; 11% had shown no evidence of change; and 2% had shown evidence of an increase in the reproductive number by 2007. Although imperfect, this simple comparison illustrates that despite warming global temperatures, the combined natural and anthropogenic forces acting on the disease throughout the twentieth century have resulted in the great majority of locations undergoing a net reduction in transmission between one and three orders of magnitude [emphasis added, Eds.] larger than the maximum future increases proposed under temperature-based climate change scenarios…When compared to the substantially smaller proposed magnitude of climate-induced effects, an important and simple inference is that [climate change impacts] can be offset by moderate increases in coverage levels of currently available interventions.
In other words, if we are really interested in stopping the spread of malaria, there are more effective ways of dealing with it than undertaking draconian global legislative efforts to reduce greenhouse gas levels—the equivalent of pummeling a mosquito with a sledgehammer.
Reference:
Gething, P.W., Smith, D.L., Patil, A.P., Tatem, A.J., Snow, R.W. and S.I. Hay, 2010. Climate Change and the Global Malaria Recession. Nature, 465, 342-346.
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Effective eradication programs are the only long term solution, and, we already have them. DDT used properly is most effective http://rachelwaswrong.org/malaria-legacy/ . Good roads. stable governments and literate populations all help in the delivery of disease relief. Until we do more in these areas no success will be achieved.
How cold do global warming people say the earth will have to be to wipe out malaria, colder than the arctic circle. Certainly colder than Finland I would think.
Or could one possibility simply be that the correlation between heat (or the lack thereof) and mosquitoes/malaria does exist and that it is the globalized temp records
over that time period that are wrong?
Also, a certain (significant?) amount of the retreat in malaria is due to habitat-loss for mosquitoes due to mostly human development (swamp draining, improved water management practices, etc.) that has implications for the local hydrological cycle and climate. In other words this info helps to corroborate the significant direct impact of human development on local temps, which go beyond simply the UHI.
May I also have a research grant, if you please? I promise I’ll only buy just one Porsche with it this time. That and my big oil money was coming from BP, and their last cheque bounced.
Martin Brumby says: But our nice friendly greenie chums, led by Rachel Carson’s pseudo science, condemned millions to die with their DDT ban.
Martin,
The Problem with our greenie chums and libtards in general is that the only thing that matters to them is INTENT. By the time the disasterous results of their good intentions occur thay have already moved on to their next project. They cannot see that in a lot of cases, the current project is to try and fix what they broke with their last project.
Birds and fish eat a lot of mosquitoes and their larvae.
Unfortunately, many swallow colonies – yep, even those famously returning to San Juan Capistrano – have been “relocated,” or simply destroyed, because some humans complained about bird droppings.
‘Same was true at Mission San Luis Obispo up the coast in Cal. – the swallows (and pigeons) were banished from the mission. Where once the sky over the mission was filled with Barn and Cliff Swallows, especially at dawn and dusk, now there are none, and the county sprays (selectively) for mosquitoes at the nearby, redundently named Lake Laguna.
A study has been done showing that Purple Martins couldn’t possibly be eating 2,000 mosquitos per day/bird based on the argument that the two species aren’t active during the same time frames.
Yes, all those Purple Martin houses were just there for the decoration.
My experience is that mosquitoes are active during the day in shady, damp areas shielded from the wind. It was one of the first lessons I learned as a youngster tromping through the woods.
Purple Martin numbers have decreased markedly, at least partialy because of competition with Starlings and English sparrows for nesting sites. Neither of these non-native, imported Eurasion species does much flycatching.
It is true that many mosquitoes hide and rest during the day on vegetation. There they are subject to predation from the many species of hunt and peck birds which scour the branches and leaves for just such resting insects. Wood warblers are a good example of birds using this hunting technique. Do they eat resting mosquitoes? I don’t know, but I would think it highly likely.
Once the balance of nature has been disturbed, man’s efforts to regain the upper hand may in fact make the situation worse. At least some species of birds have had their reproductive cycles affected by the application of DDT, and potential aquatic predators of mosquito larvae are also impacted by the pesticide.
No, Bald Eagles and Peregrine Falcons don’t eat mosquitoes, but they are birds, and both had their populations crash because of massive spraying with DDT, and that’s far from the only pesticide or herbicide being applied to the environment.
Eagles and Falcons are large, majestic, relatively easily observed species. Not so for wee mites like the American Redstart.
Finally, DDT has lost much of its former effectiveness due to over- application and resultant development of resistance in mosquitoes.
I second the observation that bugs have dropped outa sight. And so have my bats. No bugs, no bats. And with no bats, my great horned and barn owls will go away. Which means my yard will be infested with mice. Cold weather brings vermin into our living quarters, and we know what kinds of diseases those nasty little creatures carry. Trouble is, mice poison tastes good to dogs, and cheese traps snare sensitive noses. I’ve even tried live traps. Took two days to get my Jack Russell’s head out of it.
The solution? Get a cat. Perfect pest control solution. If you have a big dog, you probably want to get a big cat. However, I once had a runt cat with a crooked tail chase two German Shepherds off the property.
There were no malaria in Finland during the Winter war. The frontier was mobile and people slept in temporary quarters. The epidemics started during the Continuation war with positional warfare http://www.malariajournal.com/content/7/1/171 . Two weeks ago I collected mosquitoes in Finnish Lapland (69 degree N latitud) and got 300 Anopheles per night.
How does lowered precipitation (supposedly) affect the standing water that most mosquitos require to breed?
How do increased wind systems (supposedly) affect the ability of mosquitos to spread to and survive in non-forested regions?
How do rapidly extincting species (supposedly) affect the ability of mosquitos to obtain sustenance?
How does the invasion of shore-coupled sea-level swamp and marshland by ocean fish from sea level rise (supposedly) affect the ability of mosquitos to breed in temperate coastal regions?
How do chemical agents like DDT and logical methods like mosquito nets (confirmedly) affect the ability of mosquitos to spread deadly infectious disease?
In the immortal words of Darth Mathematician:
I sense a feedback disturbance in the Model.
Pamela Gray says:
June 17, 2010 at 7:54 am
Maybe not.
How many?
Just sayin’.
There is no need to use DDT, drain swamps or even try to control mosquitoes to eradicate malaria. In most of Europe it went extinct long before DDT was introduced and the taiga zone in northern Europe and Siberia still has vast swamp areas and even vaster numbers of mosquitoes (including Anopheles, which transmits malaria), but no malaria. As a matter of fact mosquitoes in the tropics are not nearly as numerous as they are in the taiga.
It is largely a matter of living conditions and housing.
Saw a bumper sticker on a car with Alaska plates in Florida:
“There is not a single mosquito in Alaska. They are all married with very large families.”
Um, Pam, owls eat mice and rats. Big-time.
What happens to the severity of cold and flu season in a warming world? You don’t hear warmists talking about that for some strange reason.
e_por says:
June 17, 2010 at 2:14 am
The reason for more bites of mosquitoes in warmer places has nothing to do with heat affecting the mosquitoes, rather the heat effect on people:
When it is hot, people wear less clothing, especially at night (even the modest people wear less at home). That way the mosquito have better access to human flesh.
Elementary.
Sounds reasonable to me. Even if it’s not the primary reason, it sure needs to be factored into any calculation. Just like the question: Why do most shark attacks occur in shallow water? Answer: “It’s where the people are?”
Let them believe their crazed just-so stories about stuff like this. If it’s true, then as temperature goes up, so do mosquitoes, so does malaria…thus lowering mankind’s numbers, carbon emissions, and thus temperatures.
See? Another negative feedback. 🙂
-Scott
On the use of DDT. As we are aware at this site, after a certian ‘size’ what we expect isn’t always so (take global warming!).
DDT is great for a year or two, but after that, it isn’t effect and has to be cycled out of use. The problem is that in large population you have a certian amount who are immune to any hazzard (small pox, aids, toxins, etc). Guess which set of genes get passed on to the next generation? the ones that are immue to DDT.
This has been known since the early 1960’s. Big companies (like GE) who were trying to control miquitoes at their coorporate locations were finding that the DDT seemed less effective each year. A particular professor of entomology at a specific university would get these calls and tell them ‘guess which genes get passed on?’ I know more about him than this, like he told his students ‘where ever you go, when ever you get an insect, catch three, one for your collection, and send the other two back to me for the university collection and my collection.’
What does this mean for us and DDT, let’s use it this year and next, while we work on the next toxin because that is about as long as it will be good for until the gene pool gets reshuffled.
Early Explorers to the Pacific NW of the US, noted that the Natives cooked willow bark for the medicinal properties-Quinine in partcular…-for Malaria …
Paul (June 17, 2010 at 6:27 am), great minds think alike! I, too, was wondering if the malaria stats hoisted the alarmists on their own canard, so to speak.
With more money and energy (concrete and power and pipes and transportation and electricity for water treatment plants, pumps, and sewage disposal) we could eliminate cholera as well.
But that would save people’s lives, instead of cap-and-tax carbon trading funds going to corrupt 3rd world dictoator private funds.
And some 2nd world dictators.
And quite a few 1st world democratic politicians’ well-funded allies as well.
One thing I find truly odd about the whole malaria scare connection to global warming is that apparently in the greenies magic ball of the horrid future absolute the mosquito has converted to liking dry and hot weather with not much rain and no moist and humid climate in general, instead of just rainy days with not too hot temperatures and preferably very moist and humid climate in general.
So if the greenies scenario of earth getting run over by mosquitos the it would also mean we’d get more rain in more areas, and a moist and humid climate in general, with not too hot temperatures. Uhm, isn’t that a climate change that the better part of the African continent, and several Arabic nations, and Persia, and parts of China, oh and Russia, and Australia, and parts of US, ah yes and Mexico, oh sod Spain, France, and Portugal, really needs, or rather needed yesterday already? Hmm funny how the mosquitos need for proper climate meet the human agriculture need for better climate. :p
Pamela Gray says:
June 17, 2010 at 7:54 am
I’ve even tried live traps. Took two days to get my Jack Russell’s head out of it.
The solution? Get a cat. Perfect pest control solution.
And what’s wrong with your Jack Russell killing vermin?
Excellent another paper for the list (now over 750)
700 Peer-Reviewed Papers Supporting Skepticism of “Man-Made” Global Warming Alarm
AC, you misunderstand the way in which DDT is used now to control malaria. It’s used to treat surfaces in houses (maybe external surfaces, too, not sure about that). The mosquitoes that come into close proximity with sleeping people (the highest risk time for pathogen transmission) hit the DDT first and die before they bite. Not enough of the total moquito population is exposed to the DDT to create the kind of selection pressure that would generate a resistant population. It’s not foolproof, but it’s a damn sight better than nothing. A lot of enviros basically regard Africans as expendable- disturbing but true.
I do think if a man is going to post a 2-hour presentation on the internet both attacking someone’s work and attempting to discredit them, then that man should respond to letters from the person whom he targeted in his presentation.
Just as AIDS was and is a political problem, so will Malaria become one.
Lots of people will die if Malaria is connected to the political bandwagon that is Agw.