The muddy soil in the glade is carpeted with male butterflies, which settle to imbibing the mineral-rich moisture. They obtain vital chemicals this way, which they pass to females during copulation. There are so many butterflies here that it is impossible to walk without treading on them. Amongst them are brilliant metallic green Caria Metalmarks, red Marpesia Daggerwings, black and orange Riodina, and the stunning purple Rhetus periander. At the edge of the glade we watch a Starry Night Hamadryas velutina basking head-downwards on a tree trunk. It is possibly the most beautiful butterfly we have seen today, its large velvety black wings adorned with hundreds of shimmering blue spots.

11.00am - It is hot now, and the forest resounds with the call of giant cicadas. The sound begins as a slow hesitant clicking, gradually accelerates to a rattle, then a hum, and escalates into a haunting siren wail which fills the air for a few moments before fading again into silence.

In the afternoon we travel upriver by dugout canoe. Amazon kingfishers swoop past, a harpy eagle hovers high in the sky above us. On a nearby rocky island we see a caiman basking, and along the riverbanks we see sun bitterns and the very beautiful capped heron.

Strings of bright yellow Phoebis butterflies fly in follow-the-leader fashion along the river's edge. Sometimes hundreds gather to imbibe moisture on the sandbanks, erupting into flight as our boat passes. We notice how most species of butterfly congregate with their own kind - there are clusters of Marpesia Daggerwings, groups of Heraclides Swallowtails, tightly packed clusters of Protesilaus Swordtails, and gatherings of bright orange Julias. Many different species arrive and depart during the course of the day, until late afternoon when swirling swarms of Eunica Purplewings oust almost every other species.

We stop at various places along the river to explore the trails. Imaginary snakes wait to strike from behind every tree - but they are not all imaginary. Clambering up a riverbank we are suddenly confronted by a gigantic anaconda with a massive head and a body perhaps 8 metres or more in length. Luckily for us it has already eaten - it's belly greatly distended by the capybara which became it's breakfast !

As the day cools down, we journey back along the river. Beautiful birds fly across our path - green ibis, ringed kingfisher, striated heron, kiskadee, paradise jacamar. A giant river otter inquisitively pops it's head out of the water next to the boat. A capybara, looking like an enormous guinea pig, looks across at us from the riverbank. During the next half hour we see a dozen tapirs, amongst the most enchanting and gentle of all animals, emerging from the forest at different spots along the riverbank.

Back at our base the light is fading fast, and the howler monkeys roar again. We sit down for our evening meal, comparing notes about the wonders we have seen, and agree that this is probably the most wonderful place on Earth.

Rio Madre de Dios, Peru

The next morning we travel downstream for an hour, disembark from our dugout, and get into a jeep. We leave behind the beautiful pristine rainforest, travelling through secondary forest, and then for several miles through cattle pastures, until we come to the town where we catch a plane to our next destination.

For 4 hours we fly across what was formerly rainforest, but all we see is a huge expanse of semi-desert. The forest has all been burnt down and turned into cattle pasture, but the pasture only lasts for a few years, and all that remains now is a barren dusty landscape dotted with termite mounds. Looking down from our plane we see a dead parched world, devoid of life.

We have been told that our next destination is an oasis - an "island" of pristine rainforest that has miraculously survived amidst a desert of failed cattle ranches in the state of Rondonia. Our plane lands and we board a bus. For the next 5 hours we are driven across 200 miles of devastated land. The forest has gone, the cattle ranches have failed, and the air is hot, dry and dusty.

By the time we arrive at our base we have a feeling of the most intense grief. Many of us, all grown men, are in a state of stunned silence, close to tears. We have left the most wonderful and precious environment imaginable, and now realise the full horror of what is happening in Brazil. The foul air around us is thick with smoke, our eyes are watering, and we are struggling to breathe.

Pristine rainforest deliberately burnt for conversion to cattle pastures

The spot where we are now standing was once the richest butterfly site known on Earth. Just 30 years ago it supported over 1500 butterfly species, but now they are very scarce. Within 5 years they will almost certainly be lost forever. For 4 days we search the tiny fragment of forest that still remains here, looking in vain for butterflies, muttering in disbelief at what has happened here.