The real butterfly effect

NASA/James Acker.

NASA/James Acker.

In Chaos Theory, the but­ter­fly effect refers to the notion that a small change at one place can res­ult in much lar­ger dif­fer­ences to a later state. The example used to illus­trate this – and which gives the phe­nomenon its rather poetic name – is that of a hurricane’s devel­op­ment being con­tin­gent upon the flap­ping of a butterfly’s wings some time before. Well, pos­sibly a more obvi­ous ‘but­ter­fly effect’ has been recor­ded by NASA (the USA’s National Aeronautics and Space Administration) with its Aura satel­lite. One of its images (pic­tured here) – of NO2 levels in cent­ral Africa in July 2011 – shows a red butterfly-like pat­tern that rep­res­ents the highest levels of NO2 over the south­ern Democratic Republic of the Congo. The NO2 res­ults from agri­cul­tural fires in which cro­p­lands are burnt to clear fields post-harvest, and to encour­age new growth in pas­tures for graz­ing animals.

Unfortunately, NO2 is a major air pol­lut­ant that gen­er­ates low-level ozone in the pres­ence of sun­light, which in turn con­trib­utes to smog and poor air qual­ity. And being gaseous the effects are felt not just in the vicin­ity of the fires, but demo­crat­ic­ally shared fur­ther afield; the smog affects plants and anim­als, con­trib­ut­ing to res­pir­at­ory prob­lems in humans. In addi­tion to NO2, the satellite-mounted ozone mon­it­or­ing instru­ment (OMI) gives daily global cov­er­age of key air qual­ity com­pon­ents such as SO2 and aer­o­sol char­ac­ter­ist­ics, and provides map­ping of pol­lu­tion products from an urban to super-regional scale. Although record­ing these poten­tially dam­aging pol­lu­tion events doesn’t neces­sar­ily stop them being pro­duced it is an import­ant step in under­stand­ing their source and prevalence.

Nigel Chaffey. ORCID 0000-0002-4231-9082

Nigel is a botanist and full-time academic at Bath Spa University (Bath, near Bristol, UK). As News Editor for the Annals of Botany he contributes the monthly Plant Cuttings column to that august international botanical organ. His main goal is to inform (hopefully, in an educational, and entertaining way...) about plants and plant-people interactions.