Ali Noorani is the executive director of the National Immigration Forum , an organization based in Washington that advocates for the value of immigrants. You can follow him @anoorani. The opinions expressed in this commentary are solely those of the author.

They are worlds apart.

In the past two years, President-elect Donald Trump campaigned on promises ranging from the mass deportation of 11 million undocumented immigrants to building a wall along the entirety of the U.S.-Mexico border to temporarily banning refugees, Christian, Muslim and beyond, from particular regions.

If Trump attempts to translate these proposals into policies, led by hand-picked, compliant personnel, these actions would initiate a human tragedy — full stop.

U.S. citizen children would face the deportation of undocumented parents, leaving gaping holes in our communities.

The impact on America's families, and the values we share as Americans, would cut deep and wide. This would be rivaled only by the actual economic costs, to the tune of hundreds of billions of dollars. And, in the end, the return on investment would be astonishingly small in terms of national security.

According to the American Action Forum, mass deportation would cost taxpayers somewhere in the range of $400 billion to $600 billion. And that's just for starters: The hit to the labor force would gut our gross domestic product by $1.6 trillion.

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Meanwhile, experts at the Massachusetts Institute of Technology reviewed Trump's border wall proposal and concluded a 1,000-mile wall would cost anywhere from $27 billion to $40 billion.

We don't have that kind of spare change lying around. And the legally dubious idea that Mexico will pay for a wall is beyond a stretch. "Paying for a wall is not part of our vision," Mexican Foreign Minister Claudia Ruiz Massieu reiterated Wednesday.

Our safety and security are paramount. But there are better ways to guarantee effective barriers at our borders. For example, physical barriers already exist along much of the Southern border, and technology is amplifying our security. Improving the infrastructure and personnel at points of entry would be a smart starting point to border security.

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Will Trump get the full picture about this from his trusted advisers? This is crucial, because tor a new White House, personnel is policy.

Over the course of the campaign, Trump surrounded himself with the full range of immigration opinions, including some who deeply believe that immigration to America should come to an end and others, particularly on Trump's evangelical advisory board, who have a more humane, compassionate approach to those who were born elsewhere.

Trump's selection for secretary of the Department of Homeland Security must have a vision that balances the need for intelligent enforcement of immigration laws with the fair and humane treatment of immigrants and refugees.

From the security, financial and moral perspectives, America cannot afford a mass-deportation, build-a-wall, enforcement-only Department of Homeland Security.

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And Americans don't want it, either — not even Trump supporters. Polls in September and October showed that 60% of Trump supporters supported allowing eventual, accountable legalized status and citizenship for people here without authorization. Less than a third of Trump-supporter respondents in both polls supported mass deportation.

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One of the most important policy decisions for the Trump administration will be what to do with respect to Deferred Action for Childhood Arrivals, known as DACA. This program allows law enforcement to prioritize the pursuit, detention and deportation of true threats, not young people who know only America as home. And it allows those young people to study, work and contribute more fully, as hundreds of thousands are doing.

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Should the Trump administration move to repeal DACA, which has never been successfully challenged in the courts, America will be reminded in no uncertain terms who is undocumented. It is a co-worker, a member of the family next door, your child's friend, the family who sits one pew over in church.

These are among the immigrant families who are afraid Trump's campaign promises will become Trump's administration policies.

Governing is not campaigning. Real lives and real money are on the line.

How President-elect Trump proceeds on immigration will define who we are as a nation for generations to come.