Jungle fever: A longboat on the Napo river

Ecuador's Yasuní National Park is rich in biodiversity, but the oilfields below it are equally as prized, says Ben Westwood

We'd been waiting for more than two hours, and I was beginning to wonder if they would show up at all. Suddenly one appeared, then another and another until the trees were teeming with dozens of them, and the air was filled with their chattering chorus. Within minutes they reached a pool at the cave mouth, where they drank and pecked at the clay, jostling for space in a green-and-red feeding frenzy. Then without warning they took flight and shot straight towards us, forcing me to duck as they flew through the observation lodge.

I was witnessing what my guide had billed – without exaggeration, it seemed – as "one of the most amazing spectacles in nature": flocks of cobalt-winged parakeets drinking at the clay licks in Yasuní National Park in eastern Ecuador. It was made all the more impressive because we were lucky to have seen them at all. The parakeets descended so slowly because they were watching for birds of prey.

Yasuní epitomises the biodiversity that makes Ecuador so special. Just consider some of the numbers: 25,000 varieties of plants, more species than in all North America and 1,676 types of birds (one in five of the world's species). The jewel in Ecuador's ecological crown is Yasuní, its largest mainland national park. The terrain contains upland tropical forest, seasonally flooded forest, marshes, swamps, lakes and rivers. It's not only a birdwatcher's dream, but home to weird and wonderful mammals: from the world's smallest monkey (the pygmy marmoset) to the world's largest rodent, the capybara. Add in jaguars, pumas, tapirs, dolphins, giant otters and (thankfully elusive) anacondas, and Yasuní is clearly a special place.

Unfortunately, Yasuní's riches are not confined to its rainforest. Underneath the park are the oilfields of Ishpingo, Tambococha and Tiputini (ITT), which supposedly contain one billion barrels of the black stuff. The pressure to drill has become almost irresistible. However, the people of Amazonian Ecuador are aware of the devastation caused by oil – vast tracts of rainforest have been cleared, waters polluted and communities poisoned since the country's oil boom began in the 1970s. So the Ecuadorian government came up with a plan. The central idea of the Yasuní ITT project is for developed nations to pay Ecuador $3.6bn (about half the value of the oil) to keep it underground. It seems a fine notion, but the timing could not be worse; in the midst of the worst economic crisis in generations, governments have been slow to commit and officials are threatening to start oil exploration if $100m is not raised by the end of this year.

I wanted to see Yasuní before it was too late. My journey started at the docks at the the oil town of Coca, for a motorised canoe ride down the Napo river. The forest became denser as the settlements outside Coca faded from view and the town's towering bridge was replaced by towering kapok trees standing 45 metres above the forest canopy. Our canoe meandered for more than two hours past the sandbanks in the middle of the murky waters before we reached a beach of surprisingly fine sand. Then on a short trek through the jungle, the hum of the motorised canoe was supplanted by the hum of insects and calls of countless birds. As our boat inched through flooded rainforest, we spotted a rich variety of species – grey-headed Tanager, greater yellow-headed vulture, gilded barbet and a chestnut woodpecker in the trees, and egrets and herons in the water.

I was staying at La Selva Jungle Lodge, with a dramatic location on Lake Garzacocha. Even more dramatic was the organised jungle walk we took that night. The first stop was to the tarantula holes, rather too close to the lodge for comfort. Tarantulas, said my guide, get a bad press and are mostly harmless and docile, their bite no stronger than a wasp sting. Far more vicious are conga ants; we passed a nest further down the trail. Nicknamed "24-hour ants" for the day of pain and fever that follows a bite, these are the largest species in the jungle and highly aggressive. On the water, the feared anaconda remained elusive, but with our flashlights we could make out the eyes of white caiman watching us intently.

The next day we crossed the Napo river into YasuníNational Park. Tourists can visit only the fringes of the park near the Napo Wildlife Centre; the interior is frequented only by scientific researchers. But even the fringes are a wildlife watcher's dream, with more than 500 species of birds sighted near the lodge. The first clay licks were on the riverbank where dozens of blue-headed, yellow-crowned and mealy Amazon parrots congregated to eat the clay which neutralizes toxins from seeds that make up the bulk of their diet.

As we hiked through the hills of Yasuní, our guide mixed old traditions with new by at first imitating bird songs himself and then producing an iPod with recorded sounds to tempt species closer. Equipped with a copy of The Birds Of Ecuador by Robert Ridgely and Paul Greenfield, we ticked off the buff-throated woodcreeper, black-faced antbird, rusty-belted tapaculo, red-throated caracara and red-necked woodpecker.

The next day I took the view from above the forest canopy on the lodge's 45-metre observation tower, which was built around a kapok tree. The birdwatching was spectacular, in particular a couple of amorous Amazon parrots, but the highlight was a rare glimpse of howler monkeys. After hearing the roar of the loudest land animals in the world, my guide located a solitary male on a distant branch.

I headed back to Coca the next day, where the presence of the oil industry on the fringes of Yasuní was obvious. Trucks were being transported on barges across the river, dwarfing our tourist boat as we shuttled past. If the oil industry has its way, bridges and highways will cut through Yasuní – and the region will be sliced and diced in a frenzy to suck up the mineral wealth that lies beneath. I left hoping that green will triumph over black.

Ecuador facts

Population: 15,007,343
Capital: Quito
Area: 13.7 times the size of Wales
Year of independence: 1822
Opening lines of national anthem: Salve, oh Patria, mil veces! Oh Patria, gloria a ti! (Hail, oh Fatherland, a thousand times! Oh Fatherland, glory be to you!)

Travel essentials: Ecuador

Getting there

* Journey Latin America (020 8747 8315; journeylatinamerica.co.uk) has packages to Yasuní starting at £3,310 per person for a 15-day holiday taking in Quito, Otovalo, Yasuní, the volcanoes and Cuenca. The price includes flights with Iberia, transfers in Ecuador, accommodation, excursions and some meals.

* There are no direct flights between the UK and Ecuador. KLM (08705 074074; klm.com) flies from a variety of UK airports via Amsterdam, while British Airways/Iberia (0844 493 0787; ba.com) fly from Heathrow via Madrid.

Staying there

* La Selva Jungle Lodge (00 593 2255 0995; laselvajunglelodge.com).

* Napo Wildlife Centre (00 593 2 600 5893; napowildlifecenter.com).

More information

* Ecuador Tourist Board: ecuador.travel

* yasuni-itt.gob.ec * sosyasuni.org