Horse pack trips in national parks have a long history, in some cases predating the National Park Service. Yet today they remain controversial to some backcountry users who point to trail erosion and piles of horse manure.

Under an environmental assessment prepared on stock use at Yellowstone National Park, officials are proposing some slight changes to their pack trip regulations. The park's preferred alternative, Alternative C, would continue to allow up to 44 outfitters to offer pack trips in Yellowstone each year.

However, the park is seeking more flexibility to respond to resource impacts, such as over-grazing and trail damage. For example, the plan would allow the park to place limits or closures on areas of high use or where impacts occur.

In the planning documents, Yellowstone officials say they've obtained funding to hire two staffers to monitor backcountry use impacts. Along with checking on resource impacts caused by pack trips, the park's preferred alternative could involve collecting better data on hiker use in the park's backcountry; daily stock use counts; creation of a reservation system for heavily used areas of the backcountry; installation of hitching posts where needed, and; issuance of contracts that run five to 10 years.

Currently, outfitted trips bring about 9,500 head of stock into the park each year, according to the documents. The environmentally preferred alternative, which park officials are required to list in the EA, calls for an end to outfitted pack trips. However, that is not the park's preferred alternative.

The existing 10-year contracts are set to expire next month, but have been extended for one year to December 2014, so park officials can complete this environmental assessment.

Comments on the plan are being taken through December 9. You can view the documents, and comment on the plan, at this site.