Stay home to save the world? Not so fast

New research confirms that global air quality improved due to COVID-19 lockdown measures. It alsounderlines the complexity ofpolicy and lifestyle changes needed to controlpollution in the long run. 

One of the most striking effects of pandemic-related lockdowns in Europe was a brief metamorphosis of the continent’s urban environments. Places typically punctuated by noise and pollution were transformed. For many, it was a realization of the degree to which nature has been suppressed in cities, as the streets swelled with birdsong, chatter and the occasional clink of bike pedals. The pandemic ushered in an unprecedented halt in public and economic life across the globe. For Western city dwellers, the effect seemed overwhelmingly positive. But was this the case elsewhere? 

With many in the scientific community shifting their focus to the impact of lockdowns on the progression of disease, one question therefore stood out: What would the impact of this temporary “de-globalisation” be on air pollution? And if, as one would expect, the drop were to be significant, how quickly did it happen under lockdown conditions?  

Setting to work coding the parameters of lockdowns across various regions of the world and amassing pollution data, the expectation that pollution would fall was the most straightforward assumption. Whether the drop would be homogenous across countries and whether the impact of the fall would persist or fade away quickly were the more pertinent questions.  

Air quality data for 162 countries suggests that lockdown measures did indeed result in a significant decline in PM2.5 particle pollutants – the small particles in the atmosphere created by burning fuels that are regarded as most dangerous to human health. These fell by 45% when associated with domestic lockdown measures (such as school closures and curfews) and 35% with respect to broader international restrictions (such as border closures). This suggests a focus on domestic measures has a greater impact than restrictions on international movement.  

Most interesting, however, was the heterogeneity of the results – across lockdown measures, countries and types of pollution. Around 65% of countries analyzed showed air quality improvements, with Australian urban centres experiencing the biggest pollution reduction of 82%. Some lockdown trajectories were also more positive than others when it came to the collective impact on pollution reduction, COVID-19 casualties and the severity of a subsequent economic downturn.  

What we perhaps didn’t expect to find, however, is that while many countries suffered GDP losses along with reductions in air pollution, in other regions a lockdown scenario resulted in substantial GDP losses without an expected associated improvement in air quality. Most notable among them was Japan, South Korea, Greece, Colombia and Brazil. The most severe case of GDP contraction was in India, where this was met with a rise in PM2.5 pollution, while China experienced a rise in GDP, along with a slight rise in pollution. In truth, China’s outlier status skews the results, but it is notable that there is no country that approaches an ideal target of both GDP growth and a reduction in pollution. 

The unexpected rise in pollution associated with lockdown conditions in some countries speaks to differences in the composition and source of pollution. While in Europe and North America urban pollution is largely associated with industrial activity and road transport, in countries such as India and Brazil, pollution is predominantly derived from biomass burning, agriculture and residential energy use. Locking people indoors in these countries can therefore lead to a rise in residential energy use that exceeds any decline associated with a fall in road transport usage. The corollary of this finding is significant, suggesting that a reduction in economic activity and mobility may lead to a shift in economic activities that are actually more harmful for the environment.  

There are also trends and results that we cannot yet explain. Although the impact of lockdowns on countries that saw a drop in air pollution was rapid, it was also prolonged, extending over the medium term beyond the initial lockdown period. In many countries that started to open their economies up from mid-May 2020 onwards, industrial activity also increased, but without the resultant rise in air pollution that one might expect. That does not necessarily mean we can conclude that a sharp cessation of economic activity is enough to “clean the engine” and start afresh. In many cases, the picture was clouded by the fact that less strict lockdown policies were still in operation over the medium term, meaning that economic activity was not yet back at full pace.   

What these results do show, however, is the ineffectiveness of a “one-size-fits-all” approach to air pollution reduction strategies. A policy to discourage commuting may improve air quality in one region, but may have entirely the reverse effect in regions where pollution is more closely associated with resource-based economic activity. Having a broad range of policy tools at our disposal is important; although market-based environmental instruments such as emissions taxes or cap-and-trade systems have been subjected to a significant amount of critique, their impact on both prices and demand makes them effective from both an economic standpoint and in terms of freedom of action or choice. And adjustment in the price of some goods, combined with a slowdown in their production, would be relatively neutral economically, while ensuring that people are still largely given the freedom to choose the products they want to consume.  

What this study shows is that, firstly, a reduction in economic activity can have a significant and sizeable impact on air pollution. Secondly, it demonstrates the power of sacrifice and the longevity of that sacrifice. If we are willing to adjust our consumption and production practices, the goal of a sustainable equilibrium is within reach. Lastly, the policies that we develop cannot be uniform. Taxation systems need to be attuned to the industrial, production and urban structure of the country in question, with proper consideration of the sources and composition of pollution. Although we may be naturally inclined to think that time spent at home is time spent serving the best interests of the planet, it seems saving the world from your couch is only possible in specific circumstances.

This article is based on a 2021 paper (co-authored with Quentin Gallea, Dimitrija Kalanoski, Rafael Lalive, Raahil Madhok, Frederik Noack, Dominic Rohner, and Tommaso Sonno), ‘Saving the world from your couch: The heterogeneous medium-run benefits of COVID-19 lockdowns on air pollution’, which was published online by Environmental Research Letters in March 2021.