A day after pledging to open City Hall to immigrants threatened by a shift in federal policies, Boston Mayor Martin Walsh said the public is missing the larger point about the economic importance of immigration and the need for comprehensive immigration reform.

"The conversation today is dominated by me opening City Hall for a shelter and a safe haven for people, but people are completely missing the conversation on immigration," Walsh said at a New England Council event in the Financial District on Thursday morning. He added, "What we need in Washington is an immigration reform package. We don't need to build a wall, we need good, strong public policy."

President Donald Trump on Wednesday drew a sharp rebuke from Walsh and many others when he signed an executive order starting the process of building a wall along the border with Mexico and pledged to pull federal funding from so-called sanctuary cities that are more accepting of undocumented immigrants.

In one order, Trump stated his White House's policy is to "detain individuals apprehended on suspicion of violating Federal or State law, including Federal immigration law," and to "remove promptly those individuals whose legal claims to remain in the United States have been lawfully rejected."

In a second order, Trump directed federal agencies "to employ all lawful means to ensure the faithful execution of the immigration laws of the United States against all removable aliens," and instructed the attorney general to ensure that municipalities that do not comply with federal immigration law do not receive any federal funding other that what is required by law.

"Sanctuary jurisdictions across the United States willfully violate Federal law in an attempt to shield aliens from removal from the United States," the order reads. "These jurisdictions have caused immeasurable harm to the American people and to the very fabric of our Republic."

Walsh on Thursday stressed the economic impact that deportation or changes to federal immigration policy may have on the Boston area, calling immigration "an economic question on so many different fronts."

More than a quarter -- 28 percent -- of the city's residents were born in another country and 43 percent of Bostonians have at least one parent who was born elsewhere, he said. One third of the businesses in the city are owned by immigrants, Walsh said.

Taking hard-line stances on immigration, Walsh said, could also have impacts on the revenue the city sees from international tourists. In 2015, 1.6 million international tourists visited Boston and spent more than $1 billion, the mayor said.

"Can you think of the message that we're sending to other countries? 'We're deporting your people, but we want you to come here for tourism,'" he said. "That's just in the city of Boston, $1 billion."

Twenty-two percent of Boston college students and graduates are foreign-born, Walsh said, and people born in other countries make up 67 percent of the personnel in the city's thriving medical and life sciences sector.

Those students and their brainpower would be "exported" if Trump carries out his agenda on immigration, the mayor said. Walsh did acknowledge problems with the nation's current immigration laws, and said he would rather see Congress work on a path to citizenship and fixes to visa programs.

While critics of undocumented immigrants have cited burdens they place on social services, defenders of immigrants say they play a critical role in the labor force, helping to drive economic growth.

Mark Zandi, chief economist of Moody's Analytics, said at an economic conference in Boston last week that as the Baby Boomer generation ages out of the workforce, a lack of immigration would be "a very significant constraint on the economy's potential growth."

"Not only do we need to maintain the level of immigration that we have now, which is about a million per annum -- that's legal and illegal -- but we need more," Zandi said. "In fact, I think the biggest problem businesses are going to face going forward is a lack of labor. It's going to be a very tight labor market."

Zandi said he expects immigration to slow from 1 million per year to about 750,000 per year as fewer immigrants look to move to the U.S. and some undocumented immigrants "step out" of the country.