The future of outdoor recreation in the United States is in danger because of a shrinking government commitment to parks, open spaces and conservation programs at a time of growing public enthusiasm for the "great outdoors," according to a major study organized by Laurance S. Rockefeller, former chairman of the Rockefeller Brothers Fund.

The study, released yesterday by Rockefeller and six other prominent business and conservation leaders, concludes that budget cuts at all levels of government have killed the momentum that led to a vast expansion of protected wilderness areas, parks, trails and rivers in the last two decades.

Taking care not to single out the Reagan administration for criticism, the report questions several policy shifts by Interior Secretary James G. Watt, including his dismantling of the federal agency that coordinated national recreation policy and his moratorium on purchasing new park land.

"If these decisions are not considered carefully," the report says of the local and federal cutbacks, "opportunities to provide outdoor recreation resources may be lost forever and future generations will not view our stewardship kindly."

Rockefeller's assessment is considered significant because he was an architect of the last two decades of conservation laws, chairing a national commission under the Eisenhower and Kennedy administrations. The commission's recommendations led to the 1964 Wilderness Act and a range of other measures expanding protection for parks and natural areas.

The report asks Congress to create a new commission modeled on the first one, with members from both parties and private citizens appointed by the president, to chart new national policies for protecting outdoor resources in an era of fiscal constraints.

Such policies would require an expanded role for private business and public interest groups, but also an increase in federal funds "even in these difficult times" of large deficits, the report says.

It calls on the government to view outdoor recreation as a major industry ($244 billion in sales last year) and source of jobs as well as "a continuing source of national vitality at a time when society must adjust to rapid change."

The report drew a positive response from congressional leaders as well as the usually combative Watt, reflecting the eminence of its authors, who represent the moderate business-oriented segment of the conservation movement.

Aides to House Interior Committee Chairman Morris K. Udall (D-Ariz.) said he looks "positively" on the proposal for a new outdoor recreation commission. Watt stopped short of endorsing it but said in a statement that he welcomes discussion of the issue and praised Rockefeller's conservation activities as "a contribution to our society matched by very few individuals."

In addition to Rockefeller, the authors were Washington attorney Henry Diamond, a close Rockefeller associate; businessman Sheldon Coleman, chairman of the Coleman Co., one of the country's largest recreation equipment manufacturers; Patrick F. Noonan, former president of the Nature Conservancy, which sponsors private funding for major conservation projects; William K. Reilly, president of the Conservation Foundation; Emery N. Castle, president of Resources for the Future, and William Penn Mott Jr., president of the California State Parks Foundation.