"I'm not an environmentalist, I'm not a teacher, I'm not a politician," Juan Kunchiky begins. "I'm just a person that is so concerned about what is happening to the rainforest and - obviously - the people who live in the rainforests in Ecuador."
Mr Kunchiky , 28, an Amazonian Indian born in the village of Cambantsa in the heart of Ecuador's rainforest, is engaged in a unique venture aimed at raising the awareness of British pupils about environmental issues. During the past three weeks, he has seen children from about 130 schools as he tours the country spreading awareness of the threat to his homeland.
His trip has been financed by an anonymous business donation given to Plan-It Eco, a company set up by the former television producer Phil Williams and dedicated to promoting environmental understanding. It also trains teachers to tackle "green" issues in the classroom.
His talk - to pupils at St Cuthbert Mayne Roman Catholic junior school in Hemel Hempsted, Hertfordshire - starts with an indication of the size of the problem. "We're destroying the rainforests at the rate of approximately the size of a rugby field every second," Williams tells the pupils. Sixty-five per cent of all known species in the world live in the Amazonian rainforests and as a result of all the development many face the threat of extinction.
Mr Kunchiky tells how his life started "hunting and fishing and finding fruit" to feed his family - five brothers and two sisters. He belongs to a tribe of 800 people who live in the village. He sports a headband made out of toucan feathers - but insists the bird was killed as meat for food. The feathers are worn as a mark of respect.
He works now as a nature guide at Yachana Lodge - showing tourists around the rainforest and introducing them to the animals in their natural habitat. The lodge has won an international award for its work. His worry, though, is that all the its work - and the lifestyle of his family and tribe - will be threatened if the ravaging of the rainforests is allowed to go on unchecked.
"When I was living in my community, it was hard to understand the outside world," he says. "My mum - when she got ill for the first time - was taken to the big town to the hospital. We were asking her 'how big were the buses? How big were the cars?' We had never seen them before."
A pupil in the audienceasks if he has ever been attacked by any of the animals in the forests. "Usually, they don't attack because they're doing their own business," he says. "We're too big for them. Touch them or step on them by mistake and they're scared and that's when they can bite. But we co-exist with each other."
His philosophy, explained to the pupils, is that people should only take from the environment what they need to survive - and do nothing to hurt it. However, he warns: "If the rainforest disappears, the food will disappear and the people will disappear."
Williams adds: "If we carry on the way we are, we will run out of practically all rainforests by 2045-50. There will be national parks around the world but globally that's not a very good position to be in."
His message appears to have struck a chord in young hearts. Asked at the end whether they wanted to visit the rainforest, virtually everyone put their hand up. "Get your passports and we'll go tomorrow," says Williams. "Actually, no, we can't do that. But there are things we can do here to help."
That is the point of the visit. Fundesin, the foundation for which Mr Kunchiky works, has set up a website to allow schools in the UK and the Amazon to liaise with each other. The idea is that they can develop joint science projects, make pen pals and communicate about their different cultures to help increase understanding.
Most of the schools Mr Kunchiky has visited have signed up for science projects - and the demand for a visit from him this time indicates a return visit could be on the cards. Many pupils started with little understanding of the nature of the threat to the rainforests. But as one put it: "From little acorns, big oak trees can grow."