Indonesian forest fires caused largest increase in atmospheric CO2 since measurements began

Last year’s extensive forest fires in Southeast Asia, most notably Indonesia, were responsible for the highest levels of atmospheric CO2 emissions ever measured, according to research published today from King’s College London.

Writing in Nature Scientific Reports , Professor Martin Wooster from King’s and the NERC National Centre for Earth Observation, together with colleagues from institutions across Europe and Indonesia, said that last year’s record growth in CO2 was caused by the impacts of El Nino and the longterm growth in CO2 emissions from burning fossil fuels.

Much of Indonesia was naturally covered by forests, and some grew on a thick layer of moist, carbon-rich peatland storing more than 55 billion tonnes of carbon, far more carbon than is stored in their above ground vegetation. However, decades of forest clearance and the drying out of the normally moist peatlands for agriculture using extensive networks of drainage canals has made extensive parts of the Indonesian landscape much more flammable than before.

Professor Wooster, explained ‘We saw the strongest growth in the global atmospheric concentration of CO2 with an increase of more than 40% higher than the last decade’s average annual atmospheric CO2 global growth rate.

Indonesia is covered large areas of peatland and given that fire is commonly used to manage the land, every year some extend into the carbon rich peatlands, parts of which are now dry enough to burn. Major reductions in rainfall associated with the 2015 El Niño led to a much drier situation, and fires grew far larger than normal, affecting both agricultural land, forest and peatland. Levels of air pollution (locally called ’haze’) in some Indonesian cities were amongst the worst ever measured reaching some far flung locations such as Singapore.’

In addition to the extensive air pollution, the fires also led to a globally significant increase in the amount of CO2 present in Earth’s atmosphere, which the researchers estimated at 900 million tonnes (the equivalent of Europe’s total CO2 emissions for a three month period).

Professor Wooster continued. ‘Indonesia has a high number of peatlands that have been cleared of their overlying forest and will not reabsorb carbon. So emissions from these fires represent 14% of the additional atmospheric CO2 increase seen in last year compared with the average of recent years. Other potentially important contributors for the extra increase that are related to El Niño include the temporary reduced growth of plants (and hence lower CO2 uptake) due to prolonged droughts in large parts of the tropics, including Africa, and possibly reduced CO2 uptake by the oceans.

The symbolic threshold of 400 ppm has been reached in the global annual mean concentration of atmospheric CO2. Similarly the annual mean CO2 atmospheric concentration growth rate has increased from about 1 ppm in ~ 1970 towards more than 2 ppm in the last 10 year, largely due to increased burning of fossil fuels. 2015 saw the largest increase yet seen, which was contributed significantly by the 2015 El Niño driven fires, and due to the ongoing lasting drought in large parts of the tropics 2016 seems to be heading towards also showing a large annual increase in atmospheric CO2 concentration’

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