Indonesia, a vast archipelago of 17,000 islands, may conjure images of golden beaches and blue seas — but the reality may be far murkier. In December last year, the tourist island of Bali was so besieged by plastic waste washed ashore that the local government declared a "garbage emergency." Years before that crisis erupted, teenager Melati Wijsen was already campaigning to ban plastic bags in Bali — the island she grew up on. In 2013, when she was just 12 years old, Wijsen started a social initiative called Bye Bye Plastic Bags with her younger sister, Isabel Wijsen, who was 10 at that time. Their goal? To help Bali residents say no to plastic bags. Her journey in the last five years has taken her to the international stage and given her opportunities to meet world leaders and celebrities, as well as speak at global events — but there's more to be done, the 17-year-old told CNBC in Bali.

World's second largest plastic polluter

The problem with plastic in Indonesia is that it was introduced too quickly, without first educating consumers on its polluting effects, Wijsen said. Adding to that, Indonesia has a population of 264 million people, and a huge emerging market of consumers. From shampoo sachets to a handful of peanuts to keropok (a popular Indonesian rice cracker), Indonesians often buy single-use items that are contained in plastic packaging, Wijsen added. According to a 2015 report by Science journal, Indonesia is the world's second largest polluter of plastic marine waste in the world, behind only China.

Melati Wijsen and friends modelling plastic-free fashion at the International Monetary Fund-World Bank meetings in Bali Bye Bye Plastic Bags

Wijsen's passion to fight plastic pollution started when she was a student at Bali's sustainability-focused Green School. She recalls learning about inspirational leaders — such South African anti-apartheid revolutionary leader Nelson Mandela and Indian activist Mahatma Gandhi — and thinking to herself: "What can we do as kids living on the island of Bali?" Together with her sister, Wijsen started Bye Bye Plastic Bags. Through that platform, they petitioned to get citizens to support a ban on plastic bags, raised awareness and created educational materials to be distributed to primary schools in Indonesia. They eventually went on to set up other organizations, including Mountain Mamas, an initiative which teaches women living in the mountains of Bali how to make bags from donated and recycled materials. The social enterprise also gives the women additional income through the work that they do.

Isabel Wijsen (middle), co-founder of Bye Bye Plastic Bags, goes on the streets of Bali to raise awareness on plastic pollution. Bye Bye Plastic Bags

Memorandum of understanding

To get the attention of authorities, they planned in 2014 to fast from dawn until dusk each day. Wijsen explained that the sisters wanted to demonstrate they were "serious" about protecting the island. To their surprise, the governor of Bali at that time, Made Mangku Pastika, responded positively and invited them to meet him two days after they announced their demonstration. That meeting concluded with a memorandum of understanding between the governor and Bye Bye Plastic Bags. Both sides agreed to work together to get Bali residents not to use plastic bags and minimize plastic pollution. A year later, Governor Pastika announced that he wanted to make Bali plastic-free by 2018. Unfortunately, that has yet to happen, but the sisters are not deterred. Wijsen says that the political arena is an important place to be, and she wants to learn more.

Isabel and Melati Wijsen (left to right) with then-governor of Bali, Made Mangku Pastika, at the signing of their memorandum of understanding in 2014. Bye Bye Plastic Bags

"As a 17-year-old changemaker, what has been super interesting and a learning curve for me has been learning how to deal with politicians," she said, adding that it was important to understand the complex layers of a system and why it takes time for change to be implemented. "Dancing with politicians — it's three steps forward, two steps back, and then again and again. But I understand that we need to be doing it together," Wijsen added. While her journey campaigning against plastic pollution has taken her to the United Nations, as well as being invited as an inspirational speaker at the recent International Monetary Fund and World Bank meetings, Wijsen is not resting on her laurels at all.

Melati Wijsen, co-founder of Bali-based non-governmental organisation Bye Bye Plastic Bags, is getting businesses to commit to using fewer single-use plastic items. Bye Bye Plastic Bags