(CNN) — Deforestation in the Brazilian Amazon has decreased to the lowest level since record-keeping began in 1988, according to official estimates.

The country’s National Institute of Space Research studied satellite photos to determine that some 6,200 square kilometers (2,400 square miles) were deforested in the 12-month period that ended in July, the agency announced Monday. That’s an area roughly the size of the U.S. state of Delaware.

It was an 11% decrease from the amount of deforestation in the period ending in 2010, which was the previous record low.

As recently as 2004, the amount of deforestation exceeded 25,000 square kilometers (9,650 square miles), an area about the size of Vermont. With the exception of 2008, the amount of deforestation has decreased every year since then.

Of the three states with the highest amount of deforestation — Mato Grosso, Para and Rondonia — two witnessed an increase compared to last year.

Deforestation in Mato Grosso increased by 20% and in Rondonia by 6%, estimates show. Still, officials said that the creation of a crisis response group that targeted the high-risk areas kept those numbers from being even higher.

Starting in April, the space agency began to pinpoint areas with increased deforestation in real time and alert authorities, who counted on special teams of police, highway police and military officers to react and stop the activity.

The new system spotted increased activity in Mato Grosso and Rondonia.

The alerts “triggered significant operations that reduced by a lot the incidents of deforestation in Mato Grosso,” said Gilberto Camara, head of the space agency. “Because of these actions, we found that the deforestation that in April showed signs of growing, actually remained in decline for one more year.”

The country’s minister of the environment, Izabella Teixeira, added that, “This response represents a strong victory and shows that we were capable of responding quickly to the increase in illegal deforestation in the Amazon region.”

According to a report by Brazil’s National Institute for Research in the Amazon, the “modern” era of deforestation began with the construction of the Transamazon Highway in 1970. The main reason the Amazon’s forests are cleared is for cattle ranching. Large and medium-sized ranches account for about 70% of deforestation, according to the agency.

Other causes of deforestation include logging and ground fires.

Deforestation causes the loss of biodiversity, reduced rainfall and contributes to global warming, according to the agency.