The Sierra Club supports a woman's right to choose because abortion helps the environment, the environmental advocacy organization's executive director told Fox News' Tucker Carlson.

Michael Brune made the comment when the "Tucker Carlson Tonight" host asked him Thursday evening why the Sierra Club takes positions on social issues such as immigration, abortion and LGBT rights when its stated goal is to curb the impact of global warming on the environment.

As for why the club specifically takes a pro-choice stance, Brune told Carlson that abortion "helps to address the number of people we have on this planet."

Carlson, clearly surprised by the answer, challenged Brune, who moments before discussed how deporting illegal immigrants would be a human rights violation:

Given that, that that’s your position, which is a position, then the United States population has pretty much doubled in the last 50 years — it’s now at about 225-ish million people. So doubling in the last 50 years is a pretty quick rate of expansion. Most of that has come from immigration, as you know.

According to the U.S. Census Bureau, the American population is roughly 324 million.

"Why would you agitating for more immigration?" Carlson asked, seeking to understand why the Sierra Club would be pro-abortion to limit population and simultaneously supportive of immigration, which increases the population.

This is how Brune replied:

Because it's wrong, Tucker. I live in California and I have undocumented immigrants who are on my son's little league team, they go to my children's school — these are families, these are people who are part of our economy, who are part of our environment. When we go to parks, we play with them, we hangout with them. These are folks who shouldn't be deported just because of your political beliefs or other people's political beliefs — we don't think that that's right.

Carlson and the Sierra Club executive went back and forth for several more minutes about the issue, but the Fox host never got a clear answer as to how social advocacy aides the cause for a better environment.

In the final week of January, the Sierra Club issued three statements on matters seemingly unrelated to the environment.

The group slammed President Donald Trump's executive action putting a 120-day freeze on the refugee resettlement program and a 90-day moratorium on entry into the U.S. from seven Muslim-majority countries, saying in a press release the move "tramples on the American values we hold highest."

The club also condemned Trump's executive order moving forward with a border wall along the country's southern perimeter, saying his "attempt[s] to tear apart immigrant families and his scheme to wall off our country are un-American."

And when the House of Representatives voted last month in favor of a bill that would ensure taxpayer dollars never went to abortions, the Sierra Club described it as "an egregious attack on women’s rights."

Ultimately, Brune told Carlson that it's the "right thing to do" for the Sierra Club to take positions on social issues because it's an "iconic organization."

"That's fine, then go work for the [Democratic National Committee]. But you're not running an environmental group," Carlson responded. "You're running a left-wing advocacy organization where every trendy issue gets thrown into the same basket and it dilutes your mission."

"I'm just saying, you're turning off a lot of people like me, who care about the environment and want to help, but why would I sign up for this? It has nothing to do with your core mission," he concluded.