The proposed widening of Interstate 81 may affect endangered and threatened species, increase stream bank erosion, threaten historic battlefields and pave over prime farmland, according to a draft environmental study released Tuesday.

The 13 species, which are on federal and state lists, include fish, bats, mussels, plants, snails, birds and turtles.

The study used Geographical Information System data and previously known information to take a preliminary look at species, wetlands, streams, Civil War battlefields, farmland, forests, archaeological sites and other natural resources, as well as air pollution.

The study was the first of two planned environmental impact statements. A second study would involve a more detailed examination, including field research.

Both studies, in part, are examining the consequences for natural resources if the highway were widened to carry more vehicles and nearby railroad tracks were upgraded to pull more freight off the interstate.

The threatened and endangered species included the Roanoke logperch, gray bat, Indiana bat, several mussels, orangefin madtom, loggerhead shrike and wood turtle.

The interstate crosses four major watersheds, including the Roanoke River and New River watersheds, from northern to southern Virginia.

Depending on how many lanes are added, the proposed widening would affect about a dozen species, about 1,000 to 1,600 acres of prime farmland, 31 to 176 acres of forest, 12 to 34 acres of open space, 1,200 to 1,600 acres of battlefields, 33 to 63 acres of wetlands and 23 to 35 miles of streams.

Air pollution would increase by less than a ton each day if two lanes were added to I-81 and would decrease by about a ton if eight lanes were added. The emissions projections were based on the premise that more lanes would mean less congestion and fewer idling engines.