Last month, federal officials said they've exceeded their limit for how many horses the area can hold.
"Our territory is supposed to have 206 to 402 animals, we have almost 4,000 horses," Modoc National Forest Supervisor Amanda McAdams said in a statement. The plateau is 258,000 acres, but McAdams said there's not nearly enough vegetation and water to support all the horses.
The horses have been feeding on limited foliage and drinking up most of the water supply, leaving little behind for other wild animals.
The government says that housing the horses long-term is too expensive, leaving adoption or sale as the most feasible option.
What will happen to the horses?
Of the 1,000 horses, about 700 are pregnant mares or under the age of 10 and will be sent to a Bureau of Land Management facility for adoption. Horses over the age of 10 will be sent to a temporary holding facility.
The older horses will be made available for 30 days to be adopted for $125 apiece.
Once the 30 days are up, those horses will be available for sale, with few limitations. Buyers can purchase up to 36 horses for as little as $1 each.
"Horses can also be sold to sanctuaries, become ranch stock horses, packing horses, or to buyers that may send them to slaughter," the agency said.
A 1971 federal law charged the Forest Service and the Bureau of Land Management with managing wild horses. For years
, the Bureau of Land Management has prohibited the sale of healthy horses to slaughterhouses. But the Forest Service is regulated by the US Department of Agriculture, which has no such prohibitions.
That's why the American Wild Horse Campaign (AWHC) is calling foul about where these horses might end up.
"It's a sad irony that the first federally protected wild horses in decades to be purposefully sold by the government for slaughter will come from California -- a state where the cruel practice of horse slaughter has been banned since the 1990s," said Suzanne Roy, executive director of the AWHC.
Why might they be shipped out of the country?
The last horse slaughterhouses in the United States closed in 2007, and eating horse meat is widely frowned upon in the United States. But it's less taboo in China and some European countries.
The AWHC accuses the Forest Service of "exploiting a legal loophole" which could allow unsuspecting people to sell horses to middlemen who would then ship truckloads of the animals to Canada and Mexico for slaughter.
"Tens of thousands (of horses) are shipped to Mexico and Canada annually, where they are killed under barbaric conditions so their meat can continue to satisfy the palates of overseas diners in countries such as Italy, France, Belgium and Japan," another animal rights group, the Animal Welfare Institute, said in a statement
The AWHC has urged the Forest Service to reduce the wild horse herds in incremental steps, where the "humane placement of horses can be assured."
But government officials say such small gathers won't be enough to cull the herds to sustainable levels.