BAR HARBOR – Elsie Flemings traded her comfortable jeans for a power suit last week as she worked for a crucial cause.

The college junior just returned from a week at the United Nations’ headquarters in New York City, where she spent 14-hour days serving as the country’s sole youth representative for the U.N.’s 14th Commission on Sustainable Development.

It was the first time since 2002 that the United States has included a youth representative on the official CSD delegation. Flemings said she was excited to have been chosen to attend the event.

“It’s really important to engage at the international level to get the change that we want,” Flemings, 23, said Wednesday. “We can’t just be working in the local level in our communities.”

It was the Boston native’s local work through the environmental organization SustainUS, however, that put her on the global radar. Her Bar Harbor-based activities with the progressive group have included organizing against “big box” stores and on fair trade, energy, climate and labor issues. The work has given her skills and policy knowledge that served her in good stead last week in New York City.

“My role there, as I saw it, was to liaison between the youth and the U.S. delegation,” she said. “It was a challenging role to play.”

For the next two years, the commission will focus on examining issues of energy, climate change, industrial development and air pollution. This year the participating countries are reviewing the global situation. Next year they will start to create policy, Flemings said. World youth want to make sure that the leaders know they’re there – and that’s where Flemings came in.

“The gaps between what the youth are advocating for, and the role the U.S. is playing with this commission, is apparent,” she said. “The delegation was very open to hearing what the youth had to say, and I was grateful for that.”

The ability to listen to youth is just a first step and will eventually lead to the creation of more pro-environment and globally considered policies, she hoped.

“We really need to see a change in the priorities of our national organizations,” Flemings said. “We need to make these issues political issues. We need our local, state and national leaders to have this as a top priority. We have to try and make our leaders listen to us.”

Flemings was bitten by the activism and social justice bugs after a high school exchange year in Beijing. She said she fell in love with Chinese culture while having her eyes opened “to the vast disparities in lifestyles, in opportunities, in issues of environmental degradation, in struggles of extreme policy.”

Once her eyes were opened, they never shut, she said.

“That was really powerful,” she said. “The more that I see, the more that I study, the more that I feel it’s really important to live with awareness of the realities of the world … and to really try to bridge that gap.”

Though Flemings knows that her work is cut out for her – a delegate she met at a previous summit on biodiversity said that she is “committed to a life of suffering” – it’s work she can’t refuse.

“It’s hard work, to be very aware of the injustice, of the poverty, the real tragedies on the ground, and then to be struggling at these various levels to be making positive change,” she said. “My hope is that we can all continue to grow in awareness of each other, as a global community … to try to create a world that is more just.”