For once, sightseers in this former whaling port can find parking places around the historic town square shaded by Hawaii's largest banyan tree.

"Business is awful," a jewelry-store manager told an inquiring tourist the other day. A hostess in a nearby empty waterfront restaurant used the same words. So did marketing aide for the luxurious Kaanapali Beach Resort complex a few miles up the sunny Maui coast.

Throughout the island, soaring air fares and the recession have retarded the tourism that directly or indirectly supports about one-fifth of the state's economy. Hotel occupancy rates, restaurant patronage, interisland air travel and advance reservations are lower than a year ago. The number of vistors, which rose 8 percent to almost 4 million in 1979, has leveled off and may actually drop this year -- for the first time since the end of World War Ii.

Though the real estate market has been cooled by high interest rates, resort and condominim construction is going on. The First Hawaiian Bank reported recently that the tourism decline has caused little economic distress so far on the "garden Isle" of Kauai because construction, which took off there in 1978, continues to boom.

Along West Maui's resort strip and on the Kona coast of the "big island" of Hawaii, more condos are going up next to new complexes with large vacancy signs.

A lot of big-time investors, from wealthy Californians and Canadians to multinational conglomerates, are obviously betting that the islands will have a brief recession and a durable allure. But even a casual tourist can also see the crosscurrents of concern about economic, social and environmental strains and the future course of tourism and development in the 50th state.

Consider three items that appeared in the Honolulu newspaper in a 10-day period last month.

The first suggested how jittery Hawaii's boosters have become about adverse publicity, in this case unfavorable -- and, some say, exaggerated -- stories in several West Coast newspapers about rising "crime in paradise."

Declaring that the bad press on the mainland had "jolted Hawaii residents," the Honolulu Advertiser ran a front page series on how Los Angeles, San Francisco, Vancouver and British Columbia, are coping with crime and harmful publicity.

Second, local photographer, writer and environmentalist Rober Wenkam, in a well-covered speech in Waikiki, hailed the decline in tourism as "some of the best news about Hawaii in a long time." Criticizing overdevelopment and plans for more growth-promoting public facilities, Wenkam asked, "When is Hawaii going to say that the islands are full?"

Two days later, a gloomy view of the next decade came from William Furtick, an agribusiness consultant and former dean of tropical agriculture at the University of Hawaii. The state's cost of living and construction costs, already high, are likely to be pushed up by rising energy and transportation bills, Furtick said. The resulting strains "could seriously curtail economic activity" and "put severe stress in the competitiveness of the Hawaii visitor industry." Social and racial tensions could also "reduce the appeal of Hawaii" for corporations and visitors, he went on.

So far, the pressures noted in these diverse stories have been most evident on Oahu, where development has been most intense, crime most conspicuous and the housing squeeze for non-affluent residents most acute. According to one recent report, the average resale price of single-family home in Honolulu was $148,000 in 1979: for a condominium, the average was $82,000.

Recently similar problems have developed elsewhere on a smaller scale. Civic leaders in Kailua-Kona, which was a languid seaside town not too long ago, are reportedly worried about over-building and harassment of tourists by youths idling on Alii Drive, the waterfront commercial street. And the manager of one sparsely-occupied resort complex there told a visitor recently that the condo boom "hasn't done much for working people here at all, except in construction and real estate."

As the comment suggests, the proliferation of resort condominiums raises some major issues of benefits and costs. Most of the publicity has emphasized the soaring prices of luxury units, especially on Maui, and the large captial gains made by early investors, including some who have bought units and sold them at high markups before they were built.

"A well-placed Hawaiian condo has been a good investment over the years as oil stocks or Krugerrands," said an article by Michael Wood in the October issue of United Arlines' Mainliner magazine.

Resort condo can also be good deals for vacationers, who can rent ample, comfortable rooms and a private kitchen at rates far below those of hotels.

From a community's perspective, however, resort condos can create fewer benefits and present more long-range problems than full-service resorts. Most of the owners -- fully 97 percent of those on Maui, according to Wood -- are non-residents. Except for real-estate commissions and taxes, the gains from all that speculation go somewhere else, often to the mainland.

Condo complexes tend to provide fewer local jobs than hotels. Because their ownership is elsewhere and fragmented, supervision of management and maintenance may be less keen.

Moreover, how much will the units be used? Under federal tax laws, an owner may occupy an investment property for only two weeks each year. Ideally, the unit will be rented the rest of the time.

But if prices and the number of units keep rising, while tourism lags, a growing share of these condos are likely to be owned by investors who are not dependent on steady rentals and may be willing to leave their vacation homes vacant for much of the year.

In the worst case, one real estate broker suggested, some of the finest shoreline in the islands could wind up being pre-empted by fully depreciated, half-empty buildings, "unless the bottom falls out of the market and islanders can afford to move in."

Some of these concerns may will be excessive. Noetheless, state officials are concerned enough that a proposed statewide tourism plan urges county governments and the state land use commission to give preference to full-service hotels "over any other type of visitor accommodations (e.g. resort condominiums)."

Among other things, the plan recommends clustering resort developments to provide more open space, conserve energy and reduce the costs of public facilities. It proposes setting new complexes back from the shoreline to preserve public access to beaches. It emphasizes the protection of important agricultural, natural and cultural areas. And it recommends "ensuring" that projects outside urban areas include enough low- and moderate-cost housing for their employees.

While proposing many controls, the plan rejects the no-growth course than Wenkam and other environmentalists espouse. "Tourism," a summary declares, "is currently the only industry which can provide enough new jobs to satisfy a growing population and keep the state's unemployment rate relatively low."

Along with related housing and natural resource plans, the tourism strategy will go before the state legislature necxt year as the next proposed step in Hawaii's continuing effort to foster steady growth without destroying the island's charms.

In the 1970s, Hawaii's pioneering state and county land-use program succeeded, at least in part, in curbing excessive, unattractive and misplaced growth. So far, as the sayings go, Kauai has not become "another Maui" nor Maui "another Waikiki."

If forecasts such as Furtick's are borne out, the 1980s will pose different, probably tougher challenges to the islands' health. Yet under the tropical skies, where the surf rolls in endlessly and the white clouds drift among the mountain peaks, it is hard to worry over ponderous problems for very long.

Somehow one is easily beguiled by the view of the Lahaina hamburger chef and part-time surfer who said, "As soon as it snows in the Midwest for a couple of months, the tourists will be back and everything will be fine."