The Colville Indian Reservation says it plans to round up about 1,000 wild horses on its land and give them up for adoption in the next few years.
The Wenatchee World reports the tribe released its plan this week.
Officials from the Confederated Tribes of the Colville Reservation say they plan to remove between 200 and 400 horses a year until about 200 are left. They say a herd can increase by 25 percent a year.
The tribe says the wild horses -- some of them abandoned by their owners who could no longer afford them -- are now overgrazing parts of the 1.4 million acre reservation.
Officials say the horses have caused significant damage to certain areas, where overgrazing has led to the spread of weeds, compacted soil and erosion.