A new study revealed that about 9,000 square kilometer of forestland, roughly about the size of Puerto Rico, in Brazil was cleared from 2008 to 2012.

The study, published in the Journal of Conservation Letters, showed that Brazil's official Monitoring Deforestation in the Brazilian Amazon by Satellite Project (PRODES) was unable to detect the deforestation that occurred beyond the primary Amazon rainforest.

"PRODES has been an incredible monitoring tool and has facilitated the successful enforcement of policies," said Leah VanWey, senior deputy director at the Institute at Brown for Environment and Society and co-author of the study, in a statement. "But we show evidence that landowners are working around it in ways that are destroying important forests."

For the study, the researchers compared data from PRODES with two independent satellite measures of the forest cover in Brazil. Their comparison revealed that deforestation in large plots of primary have declined. However, cleared areas in regions not included in PRODES monitoring have significantly increased.

Despite the vast contribution of PRODES to Brazil's reforestation efforts, the researchers discovered a major flaw in the monitoring system. The researchers found that PRODES excludes secondary forests and dry forests in its monitoring. Additionally, PRODES also treats discreet forest plots smaller than 6.25 hectares as non-forest.

The researchers fear that the flaw in PRODES monitoring system could affect Brazil's efforts to stick with the Paris Agreement. PRODES is used to calculate how much greenhouse gas the country emits through the burning of forest biomass. However, with so much deforestation occurring in areas not included in PRODES measurements, Brazil could be overestimating their emission reductions. Furthermore, the deforestation-related greenhouse emissions in Brazil could even be twice as high as PRODES estimates.

These findings clearly show that PRODES has been very effective in Brazil's battle against deforestation. However, the researchers noted that Brazil needs to update its detection and enforcement strategy not only to protect priamary Amazon rainforest, but other small forest areas as well.