I know, it’s endemic already…

From Climate Scepticism

BY JIT

I have a theory – which I may have mentioned before in these pages – that a sizeable chunk of the threat that climate change poses to the natural world could be demonstrated to be an illusion by pure logic, if anyone had the time, or as importantly the inclination, to collect the data.

There is a well-known principle in human life that looks matter. You can call this “beauty bias” if you like, or “ugly people are unfairly deemed malevolent at a glance.” Something similar occurs in the human perception of animals. Cute things are vulnerable, and horrible things are dangerous. It’s an instinct we have. See here for a discussion. There are odd-balls like me who like spiders. But that just means that the horror most people have of arachnids then rubs off on the arachnologist.

I allege that because scientists are humans and not disinterested automatons, they are more likely to look for threats against cute animals, and to look for reasons why horrible animals will spread. So goes my theory. And it would be easy to test, simply by canvassing the literature.

The climate “crisis” being the alpha and omega of threats to the natural world now, horrible creatures will swarm in the warm future, while cute things will inevitably dwindle in overbearing heat.

An example of a creature that unequivocally falls into the “horrible” caste is the mosquito, which, given the above, will therefore become more abundant and invade areas it is presently absent from, bringing with it nasty viruses or protozoans.

A BRIEF ECOLOGY LESSON (FEEL FREE TO FAST FORWARD)

You can describe the available places that a particular species might live using the concept called the “niche.” There are two main kinds.

The first is the fundamental niche, which can be thought of as an n-dimensional space with each dimension defined by some environmental parameter or another. The most obvious would be the maximum and minimum temperatures that a particular species can tolerate. There are also things like salinity and humidity and rather more intangible meteorological phenomena like rainfall. This envelope encloses the range of environments that our species could potentially inhabit.

The second kind is the realised niche. This is the subset of the fundamental niche that is actually occupied by the relevant species. As an example, there are some kinds of plant that are restricted to saltmarsh. But most of these could happily grow inland given the chance. Inland, they are easily crowded out by more vigorous species; but on the saltmarsh, their higher environmental tolerance gives them a place they can grow where the more vigorous species cannot.

END OF ECOLOGY LESSON

Using climate models, if you believe that sort of thing, you can map the present and future fundamental niche of a particular species, given information about its environmental tolerances. You can also map its realised niche from existing occurrence data, and give an impression of what its realised niche might be given a particular climate change scenario.

This is not as easy as it sounds. To take another saltmarsh example: if we think sea level is going to rise, that might mean that the realised niche of sea aster will move up the marsh. Will it though? The places into which we think sea aster is going to spread are already occupied by coarse grasses. Perhaps these will be less vigorous with an inundation or two a year – but perhaps not. Whether the community will change is not an easy matter to decide.

With that as a preamble, you’re probably beginning to wonder What The Hell Jit is on about this time. Well, I’m on about this:

THE STAR: KILLER MOZZIE TAKEOVER

DAILY MAIL: DENGUE FEVER ‘TO REACH UK’

THE SCOTSMAN: CLIMATE CHANGE COULD BRING FEVER

DAILY RECORD: TROPIC BUGS TO STRIKE UK

DAILY EXPRESS: TIGER MOSQUITOES COULD BRING DENGUE FEVER TO UK AS CLIMATE HEATS UP

THE GUARDIAN: HEALTH AGENCY SAYS CLIMATE CRISIS COULD CAUSE 10,000 EXTRA DEATHS A YEAR IN UK

A couple of weeks ago the UK Health Security Agency put out a giant report about the effects of climate change on health in, er, the UK. It can be had here. There was lots in it. But most of the papers picked up on the killer mosquito angle.

The story goes like this. There is a mosquito called Aedes albopictus, (the Asian tiger! It’s stripy, and comes from Asia, and it bites humans, get it? However, there are other stripy kinds, which could cause confusion to the non-specialist punter) which is known to transmit dengue, which will become established in the UK because Teh Climate Crisis will make the UK climate suitable for it, which will therefore lead to it transmitting dengue to hapless UK citizens minding their own business.

As it happens, the report itself is not as hysterical as the headlines. But it does itself no favours.

Here is the chain of reasoning:

A. albopictus is not in the UK.

The UK is currently not within the fundamental niche of A. albopictus, which is why it is not here.

A. albopictus has arrived in the UK and will arrive here again and again but has not established itself because it is too cold here, and would not, except…

With climate change, the UK will become suitable for A. albopictus, so that one of these colonisation events will result in the mosquito finally establishing itself.

Because A. albopictus is known to transmit dengue, it will transmit dengue when it becomes established here.

Dengue will become established in the UK, and people will die needlessly.

We have to reduce “carbon” emissions.

There are a number of problems here. According to the estimate of Proestus et al 2015, the UK is already almost entirely suitable habitat for the UK. Under those estimates, climate change makes no difference to the probability of establishment of the mosquito, even using the deprecated RCP8.5 Armageddon scenario (spot the difference in the two maps below). And if it is true that the UK is not currently suitable, it perhaps would have been better if the UKHSA had not also used RCP8.5 scenario to predict future temperatures.

The next point is that even though a habitat is physically suitable (remembering the fundamental niche concept) it does not follow necessarily that a species will become established, because ecological interactions come into play (the realised niche). There are already plenty of mosquitoes in the genus Aedes in the UK, and it is at least plausible that the newcomer will fail to establish because of competition with the incumbents, particularly through the production of low-fitness hybrids (so-called “satyrisation” – discussed in relation to this species and A. aegypti by Lounibos & Juliano 2018). If the mosquitoes do become established, there is no reason to suppose that dengue will become established. One particular problem is that to transmit dengue, a mosquito has to bite an infected human, and then bite a non-infected human. As the only source of dengue is imported humans, this process is inevitably a rare and therefore unlikely occurrence. Humans in the UK just do not get bitten as much as people in some parts of the world, because we have better-quality housing (pro tem) than many parts of the world. There may be little flare-ups of dengue based around one individual, but it seems unlikely that this will persist. This is particularly the case because we have this thing called winter, which would enable infected individuals to clear the virus before mosquitoes become active in the following summer. That is the case come hell, high water, or RCP8.5.

In my estimation, there is not a cat’s chance in hell that dengue will become established in the UK. I would not, however, be surprised if A. albopictus becomes established here. But there is no need to panic. Introduced species are by and large not as terrifying as they are predicted to be. What proportion of introduced species live up to the hype around their arrival is another interesting topic.

As for satyrisation reducing the fitness of invasive mosquitoes: do satyrs have low fitness? Remember folks, it has nothing to do with their looks. It’s all about how well they play the flute.

Featured image

A snip from “Mosquito Extermination in New York City” by George A. Soper