"First and foremost is that shale-gas production on state forest lands is neither benign nor catastrophic," Daniel A. Devlin, the acting deputy secretary for parks and forestry, wrote in the report.
"There are clearly impacts and trade-offs associated with this activity," he wrote. "The question is, what trade-offs are acceptable."
The report carefully avoids addressing the question of acceptability, saying that the data are open to interpretation. For instance, some forest visitors might like improved roads, while others would regard them as a diminishment of the forest's wild character.
"Monitoring does not necessarily give you answers - it gives you data to be used for decision-making," Ellen Ferretti, the DCNR secretary, said in a statement.
The report will be presented to DCNR's Natural Gas Advisory Committee at a meeting Wednesday in State College. The 21-member committee is headed by Pennsylvania State University forestry professor Jim Grace.
The report is likely to provoke sharp debate and disagreement. Drilling on state forests accounts for about 15 percent of all shale gas produced in Pennsylvania.
Of 2.2 million acres of state forest land, 1.5 million lie over the Marcellus Shale, a deep deposit underlying several states that now accounts for about a fifth of the nation's gas production.
The state has leased 386,000 acres to gas drillers. Private owners control the mineral rights on an additional 287,000 acres of public land. The remaining 866,000 acres of DCNR land is unleased.
Gov. Corbett has proposed lifting a 2010 moratorium on leasing additional state forests to gas development to generate $75 million more for state coffers. The governor's office has deflected requests to identify the lands, saying the new leases won't allow any additional surface disturbance.
DCNR also faces strong opposition to drilling in Loyalsock State Forest in Lycoming County, where drillers own the mineral rights underlying a popular recreational area.
The report says that shale drilling has shifted about 9,000 acres from semi-primitive and nonmotorized land to "semi-developed and developed."
Drilling is expected to continue for decades. Producers have completed 568 of 3,000 anticipated wells on state lands.
The report says that environmental regulators investigated 324 incidents in state forests during the first five years of the shale boom, through the end of 2012, and issued 308 notices of violations.
But the frequency of incidents has slowed, the report says, and monitoring data show that "water quality has not been affected due to this activity."
DCNR's monitoring report targets a broad set of values, including water, wildlife, plants, invasive species, incidents, air quality, landscapes, soils, revenue, energy, recreation, community engagement, forest health, timber products, and infrastructure.
DCNR's full report will be available online Wednesday. Go to http://www.dcnr.state.pa.us/forestry/index.aspx and select "Shale Gas Monitoring Report."