Will redevelopment bring an '80s renaissance to Harlem?

What happens to a dream deferred? Does it dry up Like a raisin in the sun? . . . Maybe it just sags Like a heavy load . . . - Langston Hughes

Harlem is a ''dream deferred'' - but not lost.

It is sagging under a heavy load of poverty, deteriorating housing, and crime. In the past 20 years alone, it has experienced riots, unchecked decay, and an unemployment rate as great, if not greater at times, than anywhere in the US.

Now, with its vast acreage and rows of 19th-century town houses that sit on the same island as one the world's great economic hubs, Harlem is being thrust into the mainstream of city planning and urban redevelopment. There is talk of storefront improvement, a shopping mall, repairs on a railroad station, and rehabilitation of brownstones for moderate-income housing.

It is the kind of assimilation that poet Langston Hughes and other products of the ''Harlem Renaissance'' in the 1920s and '30s may never have dreamed would take place. And to many in the Harlem of the '80s, this move toward the mainstream must proceed with exceeding care.

At a recent, packed public hearing on the city's proposed redevelopment strategy for Harlem, many residents expressed concern that the plan relies too heavily on private-sector developers. City officials have reasoned that with drastic cuts in federal and state aid, they must encourage massive private investment to reverse Harlem's precipitous decline from its more prosperous past. But community leaders counter that blacks may be forced out of Harlem if private initiatives aren't intertwined with proper government restraints and supervision.

Currently, so-called central Harlem - an area roughly bounded by Central Park on the south, the Harlem River to the north, Morningside Park on the west, and Conrail tracks on the east - has a largely black population of slightly more than 100,000 people. This is a decline of more than 50,000 people during the last 10 years. In part, urban experts here say, this exodus reflects the fact that many middle-income New Yorkers of all races have fled to the suburbs in search of better housing, schools, and life styles.

But another sizable chunk of this loss can be traced to the erosion of Harlem's housing stock. Windowless, turn-of-the-century tenements line streets and avenues. Vacant lots are often less than a stone's throw away.

The enormity of Harlem's housing crisis can also be seen in the fact that 40 percent of central Harlem's buildings and vacant land is owned by the City of New York because owners failed to pay real-estate taxes.

But bit by bit signs of renewed interest in Harlem appear.

On 125th Street, Harlem's main east-west artery, ''areas of strength,'' as outlined in the city's redevelopment strategy, are evident. Whole sections of the street have been torn up and rebuilt. Parts are more pothole-free than some mid-Manhattan blocks. The famed Apollo theater, where Billie Holiday first started singing blues, is being converted into a multimillion dollar, state-of-the-art cable television production center.

''There are a lot of strong spots in Harlem,'' says Louis Winnick, an urban expert with the Ford Foundation in New York. ''But there are some sections that resemble parts of the South Bronx,'' widely considered to be one of America's worst slums.

More of Harlem might have gone the way of the South Bronx, Mr. Winnick and others insist, had it not been for Harlem's deeply rooted political and religious life. Many black political leaders, such as former Manhattan borough president Percy Sutton, who still lives in Harlem, may have added considerably to their original constituencies over the years. But they did not forget or neglect their roots, say these experts.

Another anchor of hope here - giving many residents a keen sense of community identity - is Harlem's cultural heritage, especially in music and the performing arts.

Ironically, this heritage was largely a by-product of segregation. While Ella Fitzgerald and Billie Holiday packed in audiences at the Apollo during the depression, they were barred from singing ''downtown.'' But the popularity of nightclubs in Harlem brought throngs of white and black patrons.

Yet another, darker side of Harlem was developing that would grow worse through the depression and into the '60s, when millions of federal dollars were poured into the community. This was the Harlem of poverty, drug use, and crime.

Today, the crime rate in some sections of Harlem exceeds that in parts of the South Bronx, according to recent New York City Police Department figures. Nevertheless, police officials remain hopeful that the early success of the police department ''career criminal unit'' and new efforts to crack down on drug abuse will moderate serious crime in Harlem.

Soon Harlem may have a lot more white residents. Housing costs in Manhattan's Upper East Side have already prompted some white families to locate north of 96 th Street, which used to be a dividing line between Harlem and the rest of Manhattan. A few of the area's brownstones, left over from the 1890s, have been purchased by white families at a fraction of what the buildings would be worth if they were located further downtown.

US Rep. Charles B. Rangel (D) of New York, whose district includes a wide swath of Harlem, and other blacks say they don't want to keep whites out of Harlem. But they want more blacks to be able to continue to live there in decent , affordable housing.

Mr. Rangel and others say they'll keep the pressure on City Hall to prevent redevelopment in Harlem from proceeding merely at the whim of private interests.