A new study says that warmer weather will unleash plagues as well as famines and the smiting of borders with frogs. Who saw that coming? Apart from us, who raised an eyebrow last week at the claim that cooling the planet would spread malaria since normally it is warming that unleashes the Four Horsemen of the Apocalypse (who are in fact conquest/tyranny, war, pestilence/famine and death, the last seeming vaguely redundant). And our readers, who know all effects of climate change are bad and all bad things are effects of climate change. But how bad is this one? Very. According to Nature, the study finds that “Over the next 50 years, climate change could drive more than 15,000 new cases of mammals transmitting viruses to other mammals”, which is such a tiny increase that it truly is bad that such things can get funded, published and turned into innumerate headlines in formerly scientific publications.
The Nature piece declares that “Many researchers say that the COVID-19 pandemic probably started when a previously unknown coronavirus passed from a wild animal to a human: a process called zoonotic transmission” and passes delicately over what a lot of others believe. But then it says “A predicted rise in viruses jumping between species could trigger more outbreaks, posing a serious threat to human and animal health alike” which is actually quite unlikely.
One unfortunate reason why is that the very real environmental problem of human encroachment on ecosystems has proceeded so far that in most of the world there isn’t much left unencroached. The number of unknown pathogens, and host species, in a place like Central Africa today is a mere fraction of what it was a century ago. Most of them, like Ebola, are already out and about. To say nothing of the rapid and devastating spread of diseases from animals to humans (and vice versa) in the early days of agriculture thousands of years ago, diseases that were more or less endemic in Europe and Asia by 1500 but when introduced to the Americas led to the largest mass die-off of humans, proportionally, that the world has ever seen. Compared to which, an increase in transmissions from one animal to another by 15,000 is a drop in the bucket. How many animals do you suppose there are in Africa today?
The press release, and yes it being the 21st century there is one, does tout Ebola and coronaviruses, and wave bats at us, to help scare us into forking over more research money. Because, you see, “As viruses start to jump between host species at unprecedented rates, the authors say that the impacts on conservation and human health could be stunning.” Unprecedented. Stunning. We are all going to die.
Or not, because the whole thing is a tempest in a hard drive. The study is “one of the first to predict how global warming will shift wildlife habitats and increase encounters between species capable of swapping pathogens, and to quantify how many times viruses are expected to jump between species.” But quantify is a word here meaning “make a total guess look solid by dressing it up in meretricious mathematical precision”, for instance by “projections of geographic range shifts for 3,139 mammal species” as if anyone knew that 3,139 would be on the move in half a century rather than 3,142 or 3,086 or “who knows, maybe a bunch”.
In fact the number of assumptions you have to make about how many species are capable of swapping pathogens, how readily they jump from, say, a vervet to a hippo, how often it’s happening now, how patterns of interaction will change by 2050, how much of the change is primarily driven by climate and so on once again, and the lack of solid basis for those assumptions, means you might as well have the vervet throw darts at a spreadsheet instead of biting the hippo (or vice versa).
Moreover according to Nature, “The research predicts that much of the new virus transmission will happen when species meet for the first time as they move to cooler locales because of rising temperatures.” But hang on. If they mean both species are moving to a cooler locale, they had already met and exchanged bite marks. And if one species is moving to a cooler locale and making new enemies, why wouldn’t the latter also be on the move to a still cooler spot, shifting in tandem and meeting no more often than at present? Still, the illusion of technique prevails:
“it projects that this will occur most often in species-rich ecosystems at high elevations, particularly areas of Africa and Asia, and in areas that are densely populated by humans, including Africa’s Sahel region, India and Indonesia. Assuming that the planet warms by no more than 2 °C above pre-industrial temperatures this century – a future predicted by some climate analyses – the number of first-time meetings between species will double by 2070, creating virus-transmission hotspots, the study says.”
Unless it doesn’t. But you know how it is with climate science: settled the minute doom looms. “’This work provides us with more incontrovertible evidence that the coming decades will not only be hotter, but sicker,’ says Gregory Albery, a disease ecologist at Georgetown University in Washington DC and a co-author of the study.” And
“The modelling seems ‘technically impeccable’, says Ignacio Morales-Castilla, a global-change ecologist at the University of Alcalá, Spain, although he points out that forecasting exercises such as this sometimes need to include unrealistic assumptions.”
Which in most fields would be a bit of an issue. But climate is not most fields. Thus “the researchers urge that there is no time to waste” and since one of the coauthors “says pandemic preparedness and disease surveillance are climate-change adaptation, too” there’s certainly no time to waste sending more cars from the gravy train their way.