Why do World Heritage forests­čî│release more carbon than they absorb?

The first ever scientific assessment of the amounts of greenhouse gases emitted from and absorbed by forests in UNESCO World Heritage sites has found that forests in World Heritage sites play a vital role in mitigating climate change by absorbing 190 million tons of CO2 from the atmosphere each year. However, ten forests released more carbon than they sequestered due to pressure from human activity and climate change, which is alarming.