The study concluded that this had been occurring since 1913 – an indicator showing that even forests can now affect the growth in concentration of greenhouse gasses in the atmosphere.
The study was conducted on 32 sections of forest from 1987 to 2000, with observations extending on average over 15 years.
The academics studied the link between the speed of formation of biomass and increased concentration of carbon dioxide in the atmosphere and the influence of climatic and anthropogenic factors on the amount of stored carbon – by collecting samples of wood and soil and tracking climate change.
Forests with a square area of 5.5 million sq. km. hold about 10 % of the carbon in all living organisms on Earth.
The results of the research showed that before 2013 the country’s rainforests absorbed more carbon dioxide than they emitted. But seven years ago, they began to lose carbon – losses at the moment amount to 130 kg of carbon per hectare per year.
The researchers advanced two reasons for the change. On the one hand, the sectors under study began to absorb 2.6 % less carbon dioxide per year. On the other hand, the total amount of CO2 in the atmosphere on Earth increased by 3.4 %.
The greatest change was observed in the driest and hottest regions and the researchers said the main reason behind the losses was a reduction in precipitation throughout the country (10 mm per year). Other factors were heatwaves and drought and competition between trees and other plant life in securing access to water and sunlight.
“The severe decrease in the carbon sink of the driest and warmest forests suggests that these forests may have reached a climatic stress threshold,” the report said.
In the near future, this trend will intensify and forests will begin to emit more and ore carbon dioxide, the academics concluded.
Brazil last year was struck by the highest number of forest fires recorded since observations began. A total of 6.5 million hectares was burned out.