Smog over Hangzhou, China (stock image).
Credit: © eugenesergeev / Fotolia
The startling extent to which human-made pollution is devastating China’s vital ecosystem’s ability to offset damaging carbon emissions has been revealed.
A pioneering new international study, led by the University of Exeter, has looked at the true impact air pollutants have in impeding the local vegetation’s ability to absorb and store carbon from the atmosphere.
The study looked at the combined effects that surface ozone and aerosol particles — two of the primary atmospheric pollutants linked to public health and climate change — have on China’s plant communities’ ability to act as a carbon sink.
It found that ozone vegetation damage — which weakens leaf photosynthesis by oxidizing plant cells — far outweighs any positive impact aerosol particles may have in promoting carbon uptake by scattering sunlight and cooling temperatures.
While the damage caused to these vital ecosystems in China is not irreversible, the team of experts has warned that only drastic action will offer protection against long-term global warming.
The study is published in the journal Atmospheric Chemistry and Physics.
Professor Nadine Unger, from the University of Exeter’s Mathematics department and co-author of the paper said: “We know that China suffers from the highest levels of air pollution in the world, and the adverse effects this has on human health and climate change are well documented.
“What is less clearly understood, however, is the impact it has on the regional carbon balance. The land ecosystems in China are thought to provide a natural carbon sink, but we didn’t know whether air pollution inhibited or promoted carbon uptake.
“What is clear from this study is that the negative ozone vegetation damage far outstrips any benefits that an increase in aerosol particles may have. It is a stark warning that action needs to be taken now to tackle the effects human-made pollution is having on this part of the world before it is too late.”
The team used state-of-the-art Earth System computer models, together with a vast array of existing measurement datasets, to assess the separate and combined effects of human-made ozone and aerosol pollution in Eastern China.
The study found that the Net Primary Productivity (NPP) — or the amount of carbon plants in an ecosystem can take in — is significantly reduced when the amount of surface ozone increases.
Crucially, this reduction is significantly greater than the effect aerosol particles have in encouraging plants to increase carbon intake through reducing canopy temperatures and increasing the scattering of light.
Professor Unger added: “Essentially, our results reveal a strong ‘dampening effect’ of air pollution on the land carbon uptake in China today.
“This is significant for a number of reasons, not least because the increase in surface ozone produced by human-made pollution in the region will continue to grow over the next 15 years unless something is done.
“If — and it is of course a big ‘if’ — China reduce their pollution to the maximum levels, we could reduce the amount of damage to the ecosystems by up to 70 per cent — offering protection of this critical ecosystem service and the mitigation of long-term global warming.”
Xu Yue, Nadine Unger, Kandice Harper, Xiangao Xia, Hong Liao, Tong Zhu, Jingfeng Xiao, Zhaozhong Feng, Jing Li. Ozone and haze pollution weakens net primary productivity in China. Atmospheric Chemistry and Physics, 2017; 17 (9): 6073 DOI: 10.5194/acp-17-6073-2017