There are promising results from 2015’s battle in the two decades of warfare between Black Hills National Forest and the mountain pine beetle. The latest surveys of the national forest and surrounding land show that the beetle epidemic has slowed overall, largely as a result of cutting down and sanitizing trees.

Some 16,000 to 17,000 acres of forest in the area were still infested by the mountain pine beetle last year, about the same size as in 2014, but the population of young beetles has decreased, suggesting a downward trend, Black Hills National Forest Supervisor Craig Bobzien said on Thursday.

“Our thinning the forests in those at-risk areas is resulting in the thin forests remaining green and healthy,” Bobzien said on the day the U.S. Forest Service released the results of high-resolution aerial photography and on-the-ground surveys conducted last August and September.

But the studies also deliver bad news: The on-the-ground survey registered population increases in some areas. Places that were at high risk of beetle expansion, according to the survey, were in the west central part of the Black Hills near the South Dakota-Wyoming border, the northwest corner of the Hills and southeast of Custer.

Since 1996, the mountain pine beetle has infested some 447,000 acres of forests in the Black Hills forest region, with the problem area expanding each year. The epidemic reached a peak in 2013 when 34,000 acres of forest were infested by the wood-burrowing insects.

From the Rapid City Journal: