Can preserving the planet also help feed the poor?

Nations seeking to set aside new national parks are being challenged to manage their natural areas in ways that will help meet the people's needs for firewood, food, jobs, and other necessities.

But will such new protected areas really be national parks in the century-old tradition of Yellowstone? And will the combining of national parks with ''sustainable development'' harm the natural resources and cultural values that governments are hoping to protect for present and future generations?

These are among the major issues being addressed by 400 national park and conservation professionals from more than 75 nations participating in the third, once-in-a-decade World National Parks Congress being held here.

Statistics show marked progress since the last conference, held in 1972 at Yellowstone and Grand Teton national parks:

* The number of national parks and protected areas has increased 46 percent worldwide to a total of 2,307.

* The area protected has increased 82 percent to 953 million acres.

* Twenty-nine countries have been added to the ranks of those having national parks or protected areas, bringing the total to 130.

Almost every nation with land suitable for preservation in national parks or nature reserves has already started a national park system of some sort. But competition is growing for the use of the fast-diminishing land base capable of being preserved. In the United States, national park areas are being pressured by adjacent development that is threatening park natural resources.

Since the World National Parks Congress is being held for the first time in a developing nation, the organizers in the International Union for the Conservation of Nature and Natural Resources (IUCN) chose a theme of ''parks for sustainable development.''

IUCN Director-General Lee M. Talbot says that in addition to the need for more traditional national parks with better protection, a need exists for many additional types of protected areas managed with different objectives for producing the necessary benefits to society. The possibility of any development in a national park that may harm the resources causes concern among many of the participants.

Although just starting its national park system, Indonesia will announce this week a plan for adding 11 new national park areas to the five it has proclaimed during the last three years. But one of the major questions is how to set aside areas as parks without depriving the people of their basic needs and opportunity for advancement.

Indonesian Vice-President Adam Malik stated in his opening remarks: ''In the face of poverty and hunger, how does a government allocate land? And what value should be placed on genetic resources for tomorrow in comparison to the value of exploiting natural resources for the alleviation of poverty today?''

Although such philosophical issues dominated opening speeches, most of the discussions will involve practical problems of managing and protecting national park areas and providing for scientific research. During the first week, participants will consider case studies of problems and discuss future trends in sessions covering each of the eight biogeographic realms.

And after two-day field trips to some of Indonesia's national parks and nature reserves, participants will hold three days of workshops: managing protected terrestrial areas, especially in the tropics; managing coastal and marine protected areas; and training protected area personnel.

Among subjects to be discussed in later sessions will be: the World Heritage Convention, which 65 nations have now ratified; the possibility of establishing a world national park or other types of protection for areas in Antarctica; and designation of international biosphere reserves within parks and protected areas. At a final session, participants will adopt recommendations and a general statement of principles for the future of national parks, to be called the Bali Declaration.

While the US National Park Service was the major participant in the first World National Parks Conference (in Seattle in 1962) and at the second in 1972, it is represented in Bali by only four officials and no park managers. US nongovernmental organizations, however, have sent more than 40 participants to the Bali meeting