What effects will climate change have on human health? – and not just on human health, but on animal and plant health, too! Our health depends on us having healthy crops and livestock, after all!
One problem that we need to consider is how environmental stresses may change. Currently, the climate models are predicting increased frequencies for extreme weather events – heatwaves becoming more intense and more frequent, for example; some weather events are also becoming more intense. Heavy rain is becoming heavier, in shorter but more intense downpours, and dry spells may become drier in the future, too.
In the European Heatwave of 2003, for example, it’s estimated that 20,000 people died across northern Europe due to the effects of unusually hot weather. The Guardian ran a story in February this year predicting that, by 2050, excess deaths due to hot weather could have risen by 257%.
Nor should we discount deaths due to unusually cold weather, either! University College London released a statement about some of their recent research (again, co-incidentally, in February) in which they suggest that “Climate change appears unlikely to lower winter death rates. Indeed, it may substantially increase them by driving extreme weather events and greater variation in winter temperatures”. Their research also indicates that since 1991, the main cause of variability in winter death numbers in the UK has been flu, not temperature. This contrasts with the period before 1971, when temperature was the main cause of winter mortality variations, and the period from 1971 to1991, when both temperature and flu had a role.
This brings us nicely to another aspect of health – the spread of disease. Like any other organism, pathogens such as viruses, bacteria, internal parasites and other “bugs” have their own comfort zones in which the conditions suit them. A virus that lives in a tropical fruit bat, for example, probably won’t be happy in a husky. As climate changes, these “comfort zones” will shift too. The mosquitoes that carry West Nile virus or Malaria may spread further north in the Northern Hemisphere, and further south in the Southern. Diseases currently confined largely to one part of the world may be spread by wild animals attempting to migrate to more comfortable surroundings, or by people moving in search of better living conditions.
Every time a virus or a bacterium comes into contact with a new species, there’s a potential for that pathogen to infect the new host species – and if it does, it may be because of a novel mutation, or the change of host may encourage a novel mutation. These mutations may not mean the pathogen becomes more dangerous – or less dangerous – but the potential for something that lives perfectly harmlessly in one animal to become virulently deadly and infectious in a new critter is always there. As climate change allows and indeed forces plants, animals and humans to find new places to live, the potential for disease outbreaks grows, too – outbreaks both of old diseases such as plague, malaria or TB, and also new ones we’ve never met before and have no idea (yet) how to treat.