By Adam Mynott
BBC News, Nairobi
More than 20 wildlife groups have urged Kenya's president to reverse a decision last week to downgrade Amboseli National Park to a game reserve.
Amboseli brings in about $3.3m a year from park fees
This means control of the Rift Valley wildlife haven will move from the Kenya Wildlife Service to a local authority, run by the area's Maasai community.
Opponents of the change say it is an attempt to win Maasai votes ahead of next month's constitution referendum.
But supporters say the Maasai will now benefit from Amboseli's revenue.
They say it corrects what was the "theft" of Amboseli 31 years ago, when the land was taken away from the Maasai people who had lived on it for generations.
Amboseli, internationally renowned as a haven for wildlife, particularly the huge herds of elephants that tramp across the grasslands, covers an area of nearly 400 sq km in southern Kenya.
The Maasai community will now benefit from Amboseli's revenue
It is famous for the stunning views of Mount Kilimanjaro, Africa's highest mountain, in neighbouring Tanzania.
The open letter to President Mwai Kibaki from the Born Free Foundation, the International Wildlife Coalition, the East African Wildlife Society and others says the move, known as de-gazetting, "sets a most unwelcome and potentially catastrophic precedent that could lead to the disintegration of Kenya's much envied national parks system".
Amboseli brings in about $3.3m a year from park fees and related tourist activities. This money helps administer Amboseli and other national parks in Kenya.
Wildlife tourism is one of Kenya's main sources of foreign revenue and international prestige.
Now the income from Amboseli will be administered by the Olkejuado County Council following its members' meeting with the president last week.
The decision to de-gazette Amboseli has come in the middle of a fractious political battle over a proposed new constitution for Kenya.
President Kibaki leads the campaign for a 'yes vote' in the forthcoming referendum.
Kenyan cabinet minister William ole Ntimama described the Amboseli decision as a "desperate measure to secure Maasai votes" in the referendum on 21 November.
The Maasai leaders of Olkejuado County Council are delighted to have control of such a lucrative source of income.
Opponents also claim that the move to de-gazette is illegal.