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The true impact of peatland fires has been underestimated

A new study published by Frontiers highlights the need for better mapping of peatland ecosystems and peatland fires, along with regular pre-and post-fire ground measurements. The researchers also emphasize the need for stricter forest and peatland protection policies, especially considering that their environmental impacts have been underestimated.

Global demand for wood and foods, such as soy beans, palm oil and beef, is known to fuel the deforestation of rainforests in countries such as Brazil and Indonesia. Felling these forests to make space for croplands, pastures and plantations removes the trees that would otherwise absorb and store carbon. This process also involves burning the indigenous vegetation to the ground, and even below the ground.

Although visual images of deforestation fires raging in the Amazon have become more common in the media, calculations of the total greenhouse gas (GHG) emissions reaching the atmosphere due to deforestation fires have been varied and contradictory. 

Now, Dr. Ramanan Krishnamoorti of the University of Houston has quantified the GHG emissions associated with the 2019 and 2020 deforestation fires in Brazil and Indonesia. The study also considered the contribution from the burning of peatlands – dense, waterlogged ecosystems that underlie many of the rainforests in these two countries.

“The impact that human activities are causing in forests, especially in critical ecosystems like peatlands, is not well communicated to the general audience,” explained Dr. Krishnamoorti.

“During the 2019 fire season in Indonesia and Brazil, we observed a wide range of numbers being quoted in scientific and media communications.” 

“We wanted to understand the basis of these numbers but ran into challenges accessing the data. That led us to analyze the sources of measurement and errors, how the errors are compounded over time, and their impact on policies.”

The researchers used publicly available data for deforestation in Brazil and Indonesia to estimate the total GHG impact of deforestation fires in 2019 and 2020. They analyzed available data from all Indonesian provinces, and the Legal Amazon and Pantanal regions in Brazil. They accounted for emissions from the burning of above-ground biomass, as well as from the peat soils and dry matter in peatlands. 

In Brazil, a total of 11,088 km2 of forest were destroyed between August 2019 and July 2020. In 2019, Indonesia lost 31,000 km2 of forest to deforestation fires. Many of these fires burned in carbon-rich peatland ecosystems.

Peatlands are wetland ecosystems in which waterlogged conditions prevent plant material from fully decomposing. Instead, it accumulates and becomes a dense layer of carbon-rich organic matter. Peatlands are known to store and sequester more carbon than any other type of terrestrial ecosystem. 

In the humid tropics, peat forms under conditions of high precipitation and high temperature such as are found in Brazil’s Amazon and in the rainforests of Indonesia. In these locations, peatlands underlie the rainforest trees and are exposed when the forests are cleared. 

During deforestation fires, peat ignites and burns, often underground. Peatland fires can smolder for weeks, as the dense organic matter slowly combusts. The stored carbon gets released into the atmosphere as CO2, along with other GHGs such as carbon monoxide (CO) and methane (CH4). The accompanying smoke causes a haziness of fine particulate matter that contributes to air pollution and affects wildlife and human health.

The results of the analysis, published today in Frontiers in Climate, show that Brazil and Indonesia collectively emitted nearly 2 gigatons of CO2 equivalents (CO2e) in 2019 and 1 gigaton CO2e in 2020 from the combustion of above-ground biomass. 

However, when the researchers included the emissions from deforestation fires in peatlands, the combined GHG impact in both countries increased to 3.65 gigatons CO2e in 2019 and 1.89 gigatons CO2e in 2020. This represents an increase of around 200 percent from the emissions generated by burning above-ground biomass alone. 

The results indicate that burning peatlands contributed to between 40 and 60 percent of the GHG emission impact caused by deforestation fires, in those two countries. This implies that previous estimations underrepresented the contribution of these slow-burning fires in peat ecosystems. 

In total, deforestation fires in Brazil and Indonesia accounted for three and seven percent, respectively, of the planet’s total greenhouse gas emissions in 2019 and 2020, reports the study.

“Monitoring and measurement challenges in peatlands lead to an underestimation of the true impact of deforestation fires. Since these estimates form the basis of the policy response from national governments, it results in inadequate attention to forest and peatland protection as part of climate crisis mitigation efforts,” said Krishnamoorti.

By Alison Bosman, Staff Writer

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