The Amazon is the largest rainforest in the world and naturally absorbs a lot of CO₂. Photo: Shutterstock
Temperatures are rising much faster in the Amazon region than elsewhere in the world. The extremely dry conditions and human activity are now also causing the rainforest to emit more CO₂ than it absorbs. Wageningen climate researcher Wouter Peters finds these results from his studies very worrying.
The Amazon is the largest tropical rainforest in the world. It sequesters huge amounts of carbon in the form of trees, plants, roots and other organic materials. This jungle naturally absorbs an awful lot of CO₂ through the photosynthesis reaction, which is needed for growth. It also releases large amounts of CO₂ when organic materials rot and die. For centuries this system was in equilibrium. Even the carbon that was released during naturally occurring forest fires was captured again when the trees grew back. But it seems as if that delicate balance in the Amazon forest has been disrupted in recent years. Some parts of the rainforest have even turned into a source of carbon as they have become net CO₂ emitters. That is due to both an increase in forest fires and a lack of regrowth.
This is a worrying development, says Wouter Peters, who is professor of Meteorology and Air Quality at Wageningen University & Research and professor of Atmospheric Composition Modelling at the University of Groningen. He is also associated with the Wageningen Institute for Environment and Climate Research (WIMEK). He studied the CO₂ balance in the Amazon between 2010 and 2018. He expects to have the final results by the summer but he is already prepared to conclude that parts of the Amazon forest are emitting more CO₂ than they absorb due to climate change in combination with tree felling and forest fires.
Air samples? No, they are Christmas decorations
For his research, Peters took samples of the air above the rainforest at four locations. “We flew light aircraft up to an altitude of nearly 5,000 metres and then circled downwards to 300 metres, taking an air sample every 400 metres. In total, we collected about 5,000 air samples. The CO₂ composition was then mainly analysed in Groningen.”
View of the Madeira River and surrounding rainforest near Porto Velho, Brazil, from an aircraft collecting 16 bottles of air at different altitudes in the atmosphere. Photo: Wouter Peters
During a visit to the lab in Brazil, researcher Wouter Peters freezes pure CO₂ from an air sample collected over the Amazon using liquid nitrogen. Photo: Wouter Peters
Researchers from the Gatti lab in Brazil receive training to work with the highly sensitive laser instruments, and maintain the equipment that can measure isotopes of CO₂. Photo: Wouter Peters
Incidentally, it’s a miracle that the thousands of CO₂ samples Peters had collected over all those years made it out of Brazil. “The samples were transported in glass tubes, but the air came from the Amazon. And it’s pretty tricky to get anything that comes from the Amazon through customs. To avoid any problems getting the tubes out of the country, a Brazilian employee painted nail varnish on them and labelled the box ‘Christmas decorations’.”
Arc of Deforestation
An initial analysis of the air samples shows a large difference between the eastern and western Amazon in the CO₂ absorption/emission balance. Peters says this is one of the most important findings from his research. The western region is wetter and largely untouched whereas the eastern part of the rainforest has been disrupted by tree felling to clear land and allow livestock farming and plantations. This area is also known as the Arc of Deforestation. “Our measurements show that net emissions are highest in the eastern Amazon. That is also where most tree felling takes place and most forest fires occur.” Climate change and the disruption of the natural ecosystem due to human intervention seem to be the two triggers.
The Amazon will not be able to help us bring down CO₂ levels in the atmosphere over the next century
Deforestation is releasing more and more stored CO₂, throwing the natural system out of balance. Photo: Shutterstock
The jungle naturally experiences alternating wet and dry periods and the ecosystem has adapted to that. The wet periods are characterized by torrential rain, with up to 40 centimetres per month. In the dry season, monthly precipitation is 40 mm at most. That has been the case for millions of years. Trees and plants usually survive this dry period, but the eastern Amazon was exceptionally dry in 2005, 2010 and 2015. Instead of 40 mm, it got an average of 10 mm of rain in August, September and October. That sounded the death knell for many trees. “If the drought is too intense, a lot of vegetation won’t survive. This is a worrying development because these large changes in the pattern of precipitation and drought are becoming a tipping point for the resilience of a system that has been in equilibrium for centuries.”
Peters is surprised by the speed and extent of the changes in the climate of the Amazon. “We tend to think of high latitudes, the polar regions, where the rate the ice is melting at serves as an indicator for how fast the climate is changing. But we’re seeing an astonishing increase in temperatures and decline in precipitation in the Amazon. These changes are much bigger than the average for the planet as a whole.” His research findings show that the temperature in the dry season in the eastern Amazon has risen by 2.5 degrees in the past 40 years, while precipitation has fallen by 24 per cent. There has also been a substantial increase in net CO₂ emissions. In the eastern section in particular, this is due to an increase in the number of forest fires, but it is also partly caused by a decrease in the uptake of CO₂ by the ecosystem as a result of the drier conditions. “Most climate models have assumed that the Amazon forest would help us reduce CO₂ levels by absorbing more carbon. But instead of this positive effect, in recent years we have seen a decrease in carbon sequestration and an increase in CO₂ emissions due to fires. That means this ecosystem will not be able to help bring down CO₂ levels in the atmosphere over the next century. We have always thought the Amazon was such a huge, buffered ecosystem that it was too big to fail. But perhaps that’s not the case.”
Read more about the research project on carbon cycles Read more about the research of the Wageningen Institute for Environment and Climate Research (WIMEK)