BILLINGS (AP) — A new report on threats to Yellowstone National Park reveals that National Geographic Magazine will release an issue in 2016 dedicated to the Greater Yellowstone Ecosystem. 

The issue highlighting the country’s oldest national park will come the same year the National Park Service celebrates its centennial.

The detail is in the park’s draft progress report to the United Nations Educational, Scientific and Cultural Organization World Heritage Committee. 

Park officials are required to produce the report as a condition of Yellowstone’s 2003 removal from the List of World Heritage Danger sites. 

One issue is the Yellowstone bison population, which officials say is too high. The report says the park is evaluating the feasibility of a bison quarantine program in which animals that test negative for disease could be considered for relocation outside Yellowstone and perhaps to tribal lands for conservation, cultural and commercial purposes.

The bison herd is estimated at about 4,900, and park biologists would like to keep it between 2,500 and 4,500. Up to 600 bison are scheduled for slaughter or relocation to research facilities this winter.

The report says park officials are monitoring overall changes to the geothermal system by measuring the amount of chloride leaving the park through its rivers. Variations in chloride discharge could indicate changes, but no chloride values are outside the normal range at this time, data shows. 

Air quality monitored at the west entrance to the park and at Old Faithful during the winter has improved since 2003 with reduced snowmobile traffic, according to the report. Air quality currently meets EPA standards for protection of human health but at times levels of carbon monoxide are up in high-traffic areas of the park.