It wouldn't be immediately possible to do an interview on Rio de Janeiro's polluted Olympic waterways, biologist and environmentalist Mario Moscatelli explained: he was at a convention in California.

Not a scientific convention. A Star Wars convention.

Moscatelli, 51, has been fighting to protect Rio's environment for three decades. The sci-fi film series has provided inspiration.

"I take from that story its essence, the conflict between good and bad, the question of the destruction of nature, the question of power," he says. "How this ends up destroying people, transforming people."

Moscatelli is a vociferous campaigner for the environmental protection of Guanabara Bay. Five Olympic sailing lanes are situated close to the mouth of the 318-square kilometer bay. Moscatelli says the environmental state of the area is deplorable.

Walking along the Fundão Canal, near Rio's international airport and just 15 kilometers (9.3 miles) from the Olympic race areas he gestures at the garbage carpeting the ground - a broken sofa, piles of plastic - and rancid water bubbling with toxic gasses in the stinking canal behind him.

"A rotten canal that receives all the garbage and sewage from the rivers that lead into it," Moscatelli says. "The majority of rivers that arrive in the bay are dead."

A deadly recipe of sewage and trash

The problem is two-fold: garbage thrown into rivers leading into the bay, and a lack of sanitation in the surrounding suburbs and favelas. In 2012, just 42 percent of the houses around the bay had sewage collection, according to data from the Trata Brasil sanitation institute.

Moscatelli says the untreated sewage floowing into Guanabara Bay isn't a priority for the Brazilian government

"The Brazilian authorities knew about the problem six years ago. They said they would implement a series of actions, which would be the legacy of the recuperation of the Guanabara Bay," Moscatelli says. "They simply didn't."

Across the canal the Alegria (meaning Joy) sewage plant, operates at less than half its capacity. The authorities have said a target to treat 80 percent of the raw sewage that flows in to the bay from the surrounding favelas and low income suburbs by 2016 would not now be met. But they will complete the spending of 570 million euros on sewage works by next year.

"Sanitation was never a priority of the Brazilian state," Moscatelli says.

In 2012, he led a team that replanted mangroves in the Fundão Canal as part of a bigger revitalization project. But lack of maintenance and the quantity of sewage and garbage floating down the canal has left little sign of the clean-up. The mangrove trees now sit on top of a garbage dump.

Moscatelli is scathing of palliative measures by the Rio state government such as eco-barriers to catch refuse flowing down rivers, and eco-boats, which sweep the bay picking up garbage.

"There is little to be done. Hope the state authorities block more garbage reaching the bay. Second, that they do a big clean-up in the Guanabara Bay," he says. "In relation to the sanitation, I don't see much of a solution."

A love affair with mangroves

Moscatelli has a long history of standing up to powerful interests over environmental issues. And mangroves in particular have been a recurring passion.

In 1989 he was working in environmental licensing for the nearby city of Angra dos Reis but refused to sign environmental permits for construction works that broke federal laws and threatened local mangroves. "That brought me a series of problems, death threats," Moscatelli says.

After moving back to Rio, the city he grew up in, where today he runs an environmental consulting outfit, he noticed signs that mangroves had once surrounded the Rodrigo de Freitas Lagoon, where the Olympic rowing races will be staged next year. Back then it was badly polluted. Research told Moscatelli his hunch about the former flora was right.

The mangrove trees Moscatelli planted in the Fundão Canal three years ago now are surrounded by garbage

Moscatelli resolved to bring the mangroves back. Walking around the Lagoon, he gestures towards mangrove trees he planted 27 years ago. "All these trees that we are seeing, a good part of them, were brought in my dad's car. I called it the Mangrove Mobile," he says.

This place is full of memories for Moscatelli. He even met his wife, Maria Lucia, a former schoolmate, by the Lagoon - she had been at a show, he had been working with his mangroves.

"I was mad, planting mangroves. It is like they are my children. I have two human children. But I have hundreds, thousands of tree children," he says.

A lack of shame

Although there are favelas close to the Lagoon, it is situated in an upper-middle class area of Rio. Its population put pressure on the authorities to tackle the pollution. Today it is significantly cleaner than the Fundão Canal. Moscatelli says his mangroves played a crucial part in this, acting as a "bio-chemical filter".

The tireless campaigner grumbles as he picks up a few pieces of garbage, then brightens on spotting a Socozinho bird, which nests in mangroves. "As the mangrove grew, developed, the birds returned straight away," he says. "All of this done by one biologist and often, some friends who came on the weekend."

The authorities have to be forced into action, Moscatelli says. Otherwise they do nothing. "There is not a lack of money. There is a lack of shame."