Today was a 5am start as we flew up to Flores in the Petén region of Guatemala to visit the national park and see exactly why the protection of the environment is such a vital issue here and why it has inspired such total dedication from Yuri (Melini).

It's one of those windy-up planes with propellers and there is a short intake of breath when we see it on the runway. "The Adventures of Biggles" come to mind!

It's a short, one hour flight and we fly in over pristine forest, huge lakes and finally reach what looks like a miniature version of Venice, the island town of Flores.

It is much hotter here than in Guatemala City and by the time we reach the hotel for breakfast we are already in a lather. Sitting on the terrace of the hotel, looking out over the lake it is hard to believe that this semi-paradise is also a place where human rights defenders have been attacked and killed and where, according to one source, many people don't need to work because they have made their money trading in stolen archaeological artefacts.

We drive up to the access point into the park and there, because we are with Yuri (Melini) we are ushered through as guests of the Director. The park in total is about 400 square kilometres and the part that is accessible to the public is about 4 square kilometres.

The park is home to jaguars, anteaters and many other animals and birds, and as we travel through the incredible lushness of the park, it is easy to see why it is seen as the living heart of Guatemala. The Petén region was originally 98% forested but this % is gradually shrinking as the forest is cleared, either for monoculture agriculture or cattle breeding.

We travel through the central square with its Mayan temples, the palaces of the kings and the processional routes, and it is hard to believe that these buildings dating from 1500 BC to 750 BC are only a fraction of the buildings in the whole park. The mirador site is seemingly 9 times as big, and many of the sites here have never been fully excavated and are vulnerable to robbers.

After 4 hours of trecking through the park Yuri finally brings us to temple 4 and, because Nuala and Ciaran want to interview Yuri as he is looking out over the forest, we climb up to the top. By this time every article of clothing is drenched through, but when we get to the top it is easy to see (a short attack of vertigo not withstanding) why the Petén is such a special place.

The trees stretch to the horizon and here and there in the distance you can see one of the temples emerging from the canopy and in the distance we can hear the howler monkeys roaring like lions.

As Yuri looks out over the forest he tell us this is what he lives and works for, and if he has to die to protect it then so be it. Many of the trees here are extremley valuable like mahogany and, like the tombs, are targeted by robbers.

That evening, after making our way back to the bottom, we head to Christina's house on the edge of the lake for a swim and dinner. Christina has an eco lodge and she has been a friend of Yuri's for many years. This is where he goes to escape from the constant stress.

The next morning we have to be on our best behaviour as we have an interview wth the former Governor of the Petén who has been a trenchant critic of Yuri Melini and the environmental movement. While he makes semi-complimentary remarks about Yuri in reply to a question from Mary (Lawlor), he says that in the 4 years he was governor he didn't meet one person he would consider a real human rights defender. He belives that may of these defenders simply want to get the credit of other peoples' work and get money from abroad.

It is a pity he doesn't hang around to meet with local activist, Mariela. She is a civil servant working on the protected areas and because of her work she has to have 24 hour security and has had to dramatically change her life style to not going out at night, limiting the social life of her family and constantly worrying about the safety of herself and her children.

Mariela takes us to a farm where the trees have all been burnt off to clear the ground for cattle breeding. She explains that Petén is not suitable for intensive farming as the soil is woodland soil and vulnerable to erosion. The farmers may get a short term benefit, but the cattle impact the soil and as a result the water cannot penetrate and eventually the rivers start to dry up and everybody loses.

The Petén region already gets most of its income from tourism and in her view the development of eco-tourism would be both a much more profitable option but also more sustainable in the long term.

While we are interviewing Mariela, her armed bodyguard is standing on the road watching out for her. She is a young woman with a husband and young children, yet her life is in danger because she believes in doing her job in the interest of the whole community.

At lunchtime, Yuri is leading a security workshop for 40 judges because in this country to uphold the law objectively is seen by some as a threat and an offence. One judge was shot dead last year. I asked one of the judges if she has ever considered giving up this work - she said - "Never. I knew the risks when I took on the job and despite the threats and the constant need for security I will continue my work to uphold the law as best I can".

Sometimes she receives friendly warnings, sometimes it is a direct threat that she had better look out. Like all the other human rights defenders we have met, she is aw oman of principles who believes in the common good and the importance of her work to uphold the law in the interest of the community.

There is a common thread among all the human rights defenders we meet - they may be afraid but they learn to overcome the fear, to speak out on behalf of others - and what is very clear is that international support, in whatever form it comes, is hugely important.