New research has revealed for the first time the full extent of how Artificial Light At Night (ALAN) is increasing carbon released by plants and animals across continents – without any increase in the carbon they absorb. The result is reduced carbon storage in ecosystems – which has major implications for climate models and global carbon budgets.
Artificial light at night is reshaping carbon balance of whole ecosystems
Published in Nature Climate Change, the study from researchers at Cranfield University is the first to demonstrate how ALAN is silently reshaping the carbon balance of ecosystems across entire continents.
The research team found that light pollution at night increases ecosystem respiration - when plants, microbes, and animals release carbon dioxide through activity and growth - but that there was no corresponding increase in photosynthesis, the process that removes carbon dioxide from the atmosphere.
Conducted with data from satellite observations and 86 carbon flux monitoring sites across North America and Europe, the study reveals that the effects of ALAN scale up to alter continental patterns of carbon outputs and absorption, negatively affecting whole ecosystems.
"Light pollution is one of humanity's most visible environmental changes, but its impacts are often hidden," said Dr Alice Johnston, Senior Lecturer in Environmental Data Science at Cranfield University, who led the research. "This is a widespread issue that's changing how ecosystems function, disrupting energy flows, animal behaviour, habitats and natural patterns. Put simply, brighter nights lead to greater carbon release, which is bad news for our planet."
"Around a quarter of Earth's land surface now experiences some level of artificial illumination at night," said Jim Harris, Professor of Environmental Technology and co-author of the study. "Our findings suggest that this growing footprint could subtly but significantly shift the global carbon balance if left unaddressed."
Climate models should include light pollution
Artificial light is one of the fastest-growing pollutants on the planet, increasing in radiance and extent across the land surface by around 2% each year. Yet it is not included in most climate models and global change assessments. The Cranfield team argues that it should now be considered alongside land-use and other climate drivers of carbon cycling.
Light pollution can be easily addressed, say experts
Importantly, unlike many other global climate stressors, light pollution is easily reversible.
"Unlike climate change, we could reduce light pollution almost overnight with better lighting design," said Dr Johnston. "Adopting dimmable, directional, and spectrally sensitive lighting technologies is an immediate and achievable improvement."
"Since lighting accounts for around 15% of global electricity use, and growing evidence links excessive nighttime light to negative effects on human health, tackling light pollution represents a rare win–win–win for the environment, energy efficiency, and wellbeing."
The research paper Widespread influence of artificial light at night on ecosystem metabolism is published in Nature Climate Change. The study leveraged the FLUXNET2015 network of carbon flux towers and global nighttime light datasets, enabling the detection of subtle, large-scale patterns linking light intensity to carbon exchange. The work was supported by the UK Natural Environment Research Council (NERC) [Grant NE/W003031/1].
