With increasing numbers of wildfire disasters globally, research has shown that pollutants released from wildfires can affect crops, forests and other vegetation hundreds of kilometers downwind from the source.
As global temperatures increase, moisture and precipitation levels change, and dry areas becoming drier, the likelihood of droughts and prolonged wildfire seasons are increasing.These exacerbated conditions are also likely to cause more intense and prolonged burning.
The frequency and duration of recorded wildfires have been steadily increasing since the 1980s, with nearly four times as often between 1985 and 2003. Human activities such as changes of land-use and fire exclusion are all negatively influencing wildfire occurrences. However many untouched areas are being devastated by fires, suggesting that climate change is a major factor driving the increase in global wildfires.
A recent study published in Nature Communications on December 21st, 2018 by Professor Nadine Unger of the University of Exeter, UK and Professor Xu Yue of the Institute of Atmospheric Physics, Beijing, has revealed that pollutants released by wildfires can affect crop and vegetation growth hundreds of kilometers from the fire impact zone, which were believed to be unaffected by such natural disasters.
The study investigated how ozone and aerosols (two by-products of wildfires) influences plant growth in areas that are seemingly unaffected by wildfires. It was found that there was a significant reduction in plant productivity in areas far away from the source of the fire, suggesting that fire pollution could pose a threat to region, and even global productivity with increasing global temperatures and wildfire incidences.
“The impacts of these wildfires on public health has been widely recognized, but the impact they also have on our ecosystem is less known. What we have found is that the pollutants released by these fires impacts plants in areas way beyond the boundaries of the disaster. Globally, over the past decade, fire ozone pollution reduced plant productivity substantially more than estimated drought losses,” said Professor Unger in the University of Exeter News.
The effects on the earth’s global carbon budget by fire has been well studied over the past decade. Every year, global fires emit large amounts of carbon dioxide directly into the atmosphere. This carbon loss is usually partially compensated by a boost in new ecosystem productivity due to secondary succession, in which some form of event reduces an existing ecosystem, promoting the habitation and development of new communities and populations within a given area.
Scientists were able to assess the effects of fire pollutants from 2002-2011 using state-of-the-art computer models and existing measurement datasets. It was found that the Gross Primary Productivity (GPP), effectively plant photosynthesis, was significantly reduced when surface ozone levels increased. Interestingly, reduction in GPP was not restricted to fire zones and their immediate surrounding areas, GPP reductions were identified in areas downwind from the fire sources.
The study suggests that the ecological impacts of wildfire pollution are much greater than previously thought, potentially impacting crop production that is vital to the survival of rural and developing communities.
“To the extent that we are worried about fire particulate pollution affecting human respiratory, we need to be concerned about fire ozone pollution damaging forest and agricultural productivity downwind. We are now using the UK Met Office Hadley Centre Earth System Model to predict how increasing fire activity, air pollution and drought affect the ability of the land surface to grow food and to take up carbon dioxide in the future warmer world,” said Professor Unger.
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