BRUNSWICK, Maine — Despite a petition signed by more than 500 students urging Bowdoin College to divest from investments in fossil fuels, the institution will not do so, a college spokesman said Thursday.

Student group Bowdoin Climate Action gathered signatures from 500 of the school’s 1,750 students, as well as from alumni and townspeople and met twice with Barry Mills, president of the private liberal arts college, to encourage him to follow the lead of Unity College, the first college in the country to divest from “big energy” — gas, oil and coal.

But sophomore Hugh Radcliffe of Austin, Texas, speaking for Bowdoin Climate Action, said during a conference call Thursday that those discussions were “not the most constructive,” and the administration was “not very transparent at all” when asked for figures about how much of the college’s $902.4 million endowment was invested in fossil fuels.

Mills “questions the financial ability of the college to divest and not harm financial aid,” Radcliffe said Thursday. “He’s in favor of lowering the college’s carbon footprint but not (through divesting) … he’s framing it in terms of, ‘If we divest, it may harm financial aid,’ which we disagree (with).”

Reached Thursday for comment, college spokesman Doug Cook said only, “The college has no plans to divest.” He declined to give reasons for the college’s decision or to elaborate.

Cook said he did not have figures about how much of the endowment is invested in fossil fuels.

But Bowdoin Climate Action’s campaign for divestment — one of hundreds on college campuses across the country — will continue. On Saturday evening, Bowdoin Climate Action will hold a public forum featuring, via Skype, climate activist and author Bill McKibben of 350.org, and Stephen Mulkey, president of Unity College.

In November 2012, the Unity College board of trustees voted unanimously to divest the school’s $13.5 endowment “from every industry that is polluting this planet,” according to an announcement from the college.

Mulkey wrote at the time, “The trustees have looked at the college’s finances in the context of our ethical obligations to our students, and they have chosen to make a stand,” the Bangor Daily News reported.

But Unity began its effort to divest from “big energy” five years ago, according to the college’s sustainability coordinator, Jesse Pyles, and during that time has found that, “there are opportunities out there to get the same returns or better … our returns on investment haven’t suffered (and) have tracked with the market.”

Pyles did not have exact figures on the college’s returns, but he said Unity’s approach to divestment “demonstrates that it’s possible, it’s viable, it’s doable.”

Furthermore, McKibben said, colleges are finding that they don’t actually have much of their endowments invested in fossil fuels. Middlebury College in Vermont, where McKibben teaches, invests “less than 1 percent” in fossil fuels, he said, adding, “I’d be surprised if Bowdoin had 5 percent (invested).”

Glen Brand of Sierra Club Maine, said Wednesday that the example set by Unity College “shows that the fears that the Bowdoin president and college and trustees have about this are unfounded.This is certainly the right thing to do, not only from our point of view, but a sensible economic investment, to move their investments (from) what we regard as risky dirty energy technologies to clean energy technologies.”

The campaign asks that colleges agree not to invest new money in fossil fuels, and during the next five years to “wind down” existing investments in them.

Three colleges have already committed to divesting — Unity, Hampshire and Sterling College in Vermont — and others, including Middlebury, are “considering it actively,” McKibben said.

“Schools around the country are boasting about creating sustainable campuses,” he said, but to truly do so, their portfolios must reflect that commitment. According to McKibben, four months ago, 15 college campuses had campaigns to divest from fossil fuels, but as of Wednesday, that number had grown to 234.

“The Nation magazine said two weeks ago it’s the biggest student movement in several decades,” he said. “It came out of nowhere. But 2012 was the hottest year ever seen in this country, and it reached a point where young people understand the future will not work for them unless we get climate change under control … If the fossil fuel industry carried out their business plan, then the planet tanks.”

Brand, of Sierra Club Maine, said, “This is really about undermining the social capital, so to speak, of the most powerful corporations in the world — leading us down the path of the climate crisis.”

“No one expects the divestment of one or two, or 10, or 100 colleges will hurt these companies,” Brand said. “It’s better to see this as part of a larger movement to deal with climate disruption.”

Saturday’s forum, sponsored by Bowdoin Climate Action, is scheduled to begin at 7 p.m. in Kresge Auditorium at the college. It is free and open to the public.