More ethnic diversity can mean fewer connections and less trust among citizens, says Robert Putnam, the international expert who has charted the fraying of community values in North America with his groundbreaking research.

His newest finding, bound to be controversial, even provocative, will be unveiled in Ottawa tomorrow, when Mr. Putnam speaks at a federal-government sponsored conference on "bringing communities together."

"The bottom line is that there are special challenges that are posed to building social capital by ethnic diversity," Mr. Putnam said in an interview yesterday from his home in Massachusetts. "Since ethnic diversity is in the future of the U.S. and Canada, this means we need to devote special attention to how you build connectedness or social capital in that context."

Managing ethnic diversity is a prime concern of almost every government right now -- from major initiatives within the Canadian government to the post-Taliban regime being built in Afghanistan. It is also an effort made more complex by the racial, religious and cultural tension that has become a reality of the so-called war on terrorism.

Mr. Putnam's contribution to the diversity debate comes by way of a warning -- not away from diversity, but toward more care in handling it.

In an exhaustive study, Mr. Putnam has found that social connectedness is less likely to be found in areas of the United States most affected by recent waves of immigration. And it isn't just a lack of trust between different races or cultures, but within them as well.

"It's going to be important that we redouble our efforts to build new forms of connectedness in the face of growing multicultural diversity," he says.

The Harvard professor, whose book Bowling Alone has become a Bible for people concerned about declining community values in North America, will also be talking in Ottawa about the improved but fragile state of citizens' connectedness in the wake of the Sept. 11 terrorist strikes on the United States.

Tragedy can bring out the best in societies as surely as adversity builds character in individuals, Mr. Putnam says, and indeed immediately after Sept. 11, Americans and Canadians seemed to be finding their best selves. He has tracked some of those improvements within the United States -- including a finding that inter-racial and cultural tension seemed to recede among ethnically diverse citizens.

However, Mr. Putnam is skeptical about the lasting effects of the positive fallout from the terrorist strikes. Already, he noted, church attendance has been declining to the levels seen before the tragedy.

The job of government is to seize the moment, he said, and build enduring community connections.

Canada, encouragingly, has seen a couple of examples that could have lasting, permanent implications: a rise in recruitment within the public service and in the Armed Forces. The fact that people are making long-term commitments like this may pave the way for truly significant, positive effects of the terrorist tragedy, he says.

Mr. Putnam was consulted regularly by former U.S. president Bill Clinton, and Canadian policy experts have long looked to his research as a clue to managing tough issues of diversity and community in this country.