Political conservatives are threatening conservation.

Just as the idea of preserving our historic buildings, places and landscapes has taken hold of the American mind, conservatives in Congress and the hustings are paralyzing government action.

Preservationists fear an increasing backlash, against their efforts.

Budget cuts, to begin with, are painfully drastic. When the landmark historic preservation act was passed in 1966, $200 million a year was to be spent by the federal government on the registration, restoration and protection of the country's architectural heritage.

For fiscal '79, $60 million was appropriated. For fiscal '80, it is $32.5 million.

"That's what we spend on less than seven miles of interstate highway," says Tersh Boasberg, president of the National Center for Preservation Law. The average cost per mile is $5.18 million.

An even more ominous threat to America's new and suddenly immensely popular preservation ethic is ideological rather than fiscal. The threatening ideology is, in essence, that it is none of the government's business to help preserve privately owned land or landmarks if the owner does not want it preserved.

Preservationists hold that every American has the right to his property. But no single person or interest has a right to our history.

The issue is focused on an amendment, offered by Rep. Richard Cheney (R-Wyo.), to a bill introduced by Rep. John F. Seiberling (D-Ohio). The Seiberling bill, which has a counterpart in the Senate, improves and consolidates the legislative achievements of the preservation movement. It is backed by the American Heritage Alliance, a coalition of all leading citizen organizations working to conserve our natural and historical legacy.

Cheney, who served as chief of staff for President Gerald Ford, is an influential conservative leader. His amendment would require the concurrence of the owner before a historic property can be put on the national register and thereby become eligible for federal preservation assistance in the form of tax advantages and/or grants.

The Carter administration backs this amendment. The trouble with it is that the national register was largely started to protect buildings, places or sites of certified cultural value from owners who might turn them into parking lots, high-rise offices, mines, timber crops or other profitable forms of "progress."

But 45 years after passage of the Historice Sites Act, which established the register, only 20 percent of our cultural landmarks are listed. Roughly 80 percent are still in danger and often in the hands of absentee owners, multiple owners and speculators.

As Cheney argues, landmark designation has become more than a benign plaque at the entrance. To an interested community, it opens the door to public support for turning a historic building or site into an important cultural and perhaps even economic asset.

There are possibilities for federal tax incentives to save registered buildings and tax disincentives for replacing them with new construction. Registered buildings are eligible for historic preservation grants and financial assistance from the National Endowment for the Arts, the Department of Housing and Urban Development, the Commerce Department, the Department of Energy and even the Labor Department's CETA (Comprehensive Employment and Training Act) program.

In downtown Louisville, Ky., one fine morning a year ago, the owner put an end to the argument whether or not the historic Will-Sales building should be put on the register. He blew it up. Bang!

It was his God-given property right. Patriotic appeals seldom prevail over profitable progress.

"Progress was okay," as Ogden Nash put it, "it only lasted too long."

The very idea of subordinating any other value to progress never occurred to Americans until railroads and industrial smokestacks began to invade our place to live. We thought only new things had value.

The historic preservation movement in this country -- an extension of a growing concern for "the conservation of the land for the good of man," as Clifford Pinchot put it -- began with the Antiquities Act of 1906. The National Park Service, founded in 1916, was a great help.

In 1966, with the federal bulldozers rampant to "renew" our cities and pave them over with freeways, a law was passed which extended national recognition (and the protection that recognition implied) from historic buildings to historic districts, including entire neighborhoods or towns.

But the 1966 Preservation Act is essentially concerned with federal policy. It tries to make sure that one federal agency does not destroy what another agency may hold dear -- unless, of course, it feels strongly about it.

The arbiter is the National Advisory Council on Historic Preservation, which includes all Cabinet members. Its policy to date has been to follow the path of least resistance. In the '60s, the highway interest proved to be irresistible. More lately the bullies are an alliance of developers and politicians who swing the wrecking balls in the name of more jobs and economic development.

Another problem with federal preservation action is the absence of clear administrative responsibility.

President Carter promised to fix that along with his other government reforms. I am afraid he fixed it good.

Before Carter, most federal preservation activities were under the National Park Service. Preservationists often complained that they got less attention there than Smokey the Bear.

Enter Chris Delaporte, who helped make Carter president and was promised the National Park Service for his troubles. The country's conservation groups were outraged. The Park Service, they insist, needs professional -- not political -- direction. So, as a sop, Delaporte was given the Bureau of Outdoor Recreation and, to make his domain a little larger, the unhappy preservationists were thrown into the bargain. The concoction is called the Heritage Conservation and Recreation Service.

Members of Congress and citizen organizations concerned with heritage and recreation seem unanimous, as one spokesman put it, that "Delaporte's outfit is an unmitigated disaster." Congressional dislike caused money cuts, Professional dislike caused resignations, "Chris," as the executive of a leading citizen organization told me, "caused nothing but chaos."

But then, important as it is, the federal government is not the major force in preservation. What has made the historic preservation movement strong enough to change the face of our cities, is precisely that it is a movement, a mighty popular movement.

It has become one of the most enthusiastic and intelligent citizen efforts in the history of this democracy.