Context: According to a new study, published in the journal Nature, scientists who conducted this research over a period of nine years in the eastern Amazon forests have said that "parts of the Amazon Rainforest are now releasing more carbon than they absorb".
Background

• For generations, Amazonia, which spans more than two million square miles, was a reliable carbon sink, meaning that it naturally absorbed high levels of carbon dioxide from the air, and it played an important role in keeping the global environment stable.
• However, in recent decades, humans have increasingly contributed to the degradation of the Amazon, upsetting a crucial natural balance. 
• Of the 17% of forest reduction that occurred over the last 50 years, about 14% of that loss to the agricultural industry, which has burned the land and used it for crops and livestock, the report states.
• Burning the rainforest to make room for crops or livestock can pose dangers for the climate, even decades after those fires occur. 
• Research shows that areas that were burned as long ago as 30 years back — and the accompanying decomposing trees — were still considerable sources of carbon dioxide. 
• Past fires and other factors like logging can also degrade nearby areas that were previously untouched and make those areas more susceptible to burning, according to the study.

Key Findings
Researchers who routinely tested the atmosphere at four areas in Amazonia twice a month over a nine-year period found that 

• The Amazon forests in South America, which are the largest tropical forests in the world, have started emitting carbon dioxide (CO2) instead of absorbing carbon emissions.
• Not only the Amazon rainforests, some forests in Southeast Asia have also turned into carbon sources in the last few years as a result of formation of plantations and fires.

The eastern Amazon is a hotspot of deforestation to facilitate logging and agriculture, including cattle ranches.

• The eastern areas have less moisture than the west during already-difficult dry periods, which now have become drier and have lasted longer due to climate change.

Possible Reason for Eastern Amazon Region

• Long-term decrease in rainfall and increase in temperatures during the dry season. 
• Conversion of forests into agricultural land, which has caused a 17 per cent decrease in the forest cover, an area that is almost the size of continental US.
• Deforestation and fire, among other factors, have dramatically undercut the Amazon's ability to absorb heat-trapping carbon emissions from the atmosphere.
• Another reason that they happen is when farmers burn their land to clear it for the next crop.

Conclusion: This means that if the ability of tropical forests to act as carbon sinks is to be maintained, fossil fuel emissions need to be reduced and temperature increases need to be limited as well.
About Amazon basin

• The Amazon basin is huge with an area covering over 6 million square kilometres, it is nearly twice the size of India. 
• The Amazon rainforests cover about 80 per cent of the basin and as per NASA’s Earth observatory, they are home to nearly a fifth of the world’s land species and is also home to about 30 million people including hundreds of indigenous groups and several isolated tribes.
• Other than this, the basin produces about 20 per cent of the world’s flow of freshwater into the oceans.
• Over the last few years, the forest has been under threat due to deforestation and burning.
• Deforestation in the Brazilian Amazon, which comprises about two-thirds of the area of the rainforest, started in the 1970s and 1980s when large-scale forest conversion for cattle ranching and soy cultivation began. 
• NASA’s Earth Observatory notes that state policies that encourage economic development, such as railway and road expansion projects have led to “unintentional deforestation” in the Amazon and Central America.