In the Republic of Congo where the forests meet the Atlantic Ocean, nightly patrols go out in search of giant leatherback turtles.
By John James
BBC News, Republic of Congo
After half an hour in a motorboat skimming through the maze of forested islands, treacherous sandbanks and narrow channels, the trees parted and another sound slowly drowned out the whine of the outboard motor. The roar of the sea.
Conkouati Douli is one of Congo's three national parks
In the evening sun, the horizon rose and fell in rusty, red waves as the lagoon ran into the Atlantic Ocean.
We cut the engine and jumped on to the pristine sands while our pilot Christian hid the boat in the mangroves.
'Lungs of the world'
We were searching for turtles, which were returning to the beach where they had first hatched, tasted the salty air and made their dangerous journey to the sea.
To our left the wide Atlantic swallowed the setting sun, ahead stretched yellow-grey beaches to neighbouring Gabon and to our right the dense humid forests of the Congo basin. Along with the Amazonian rainforest over the horizon, they are regarded by conservationists as the lungs of the world.
John James joins a team of researchers on their nightly patrol
"Voila, the Chinese," shouts Richard over the sound of the crashing surf. Yes, there they were, two Chinese trawler boats with nets down - clearly inside the national park's protected marine zone.
This is the area set aside to protect the whales, dolphins and turtles that come to the park. Only locals are supposed to fish here. They use hooks from the shore or in dugout canoes, which are no match for the catch-all trawlers.
Need for conservation
"The trawler men use explosives too," says Richard, a local turtle researcher. He grew up in the area and used to hunt here. But now, he says, working for the park has opened his eyes to the need for conservation.
He knows all there is to know about giant leatherback turtles. "We need to keep these animals for our children," he tells me. Apparently they are quite fussy when it comes to beaches. They need a gentle approach or a beach without rocks which could harm their soft shell. They also mate at sea. In fact, males never set foot or flipper on land after their initial journey from egg to sea.
But here in Conkouati Douli - one of Congo's three national parks - you can see the problems facing the conservationists.
As well as intensive fishing, park managers find themselves dealing with illegal gold diggers and loggers, many of whom also come from China.
I stumbled across one newly constructed settlement in the park that a Chinese firm has established to house oil prospectors. They have built hundreds of miles of roads and tracks and used underground explosions to search for oil.
The arrival of hundreds of workers is frustrating for the park authorities who had hoped to attract tourists with a newly built guesthouse overlooking the lagoon.
The park's founding statute says such exploration is illegal, but the company has a newer piece of paper from the government giving it permission to go ahead.
Threat of poachers
Congo needs new roads and bridges but conservationists question whether they should be built here. Before there were only two roads into and out of the park which the park rangers used to monitor for poachers, now it is much easier for them to evade capture. Still, some do get caught at the park checkpoints - in the past nine months, guards confiscated 16 gorillas and nine chimpanzees being taken to the local bush meat market in the city.
Unlike in East Africa where national parks are well established, they are relatively new here - Conkouati Douli was only created eight years ago and it is not yet open to tourists.
The situation, however, is much better than in the neighbouring Democratic Republic of Congo, where heavily armed militias hide out in the national parks. Here, there are men with machine guns - but they are either poachers tracking down endangered animals or park guards tracking down poachers.
Christian returns from hiding the boat, and with Richard we set of along the beach, surprising hundreds of red and yellow crabs which scuttle away from us at surprising speed.
Hundreds of red and yellow crabs scuttle away with surprising speed
After an hour's walk carrying supplies under arms, on backs and on heads we reach the shack where we willl be spending the night.
I am looking forward to a long rest, a hot meal and an early night. We did get a hot meal, but there was to be no early night.
At ten o'clock in the evening we started out along the beach. We were fortunate to have a clear sky, a bright moon and on the horizon, the lights of offshore oil platforms flickered like candles on a birthday cake.
An hour into our patrol, I get that nervous feeling common among journalists following a story. I worry that the turtles may decide this particular night is a good one to stay out at sea, to swim a bit more and chomp on some jellyfish.
But I was not to be disappointed. Fifteen minutes later a large shadow in front of us turned out to be a leatherback turtle, an animal on the critically endangered list - and this is one of the few places where you might encounter one. She was about two metres long and at that moment laying around a hundred eggs in a freshly
The Congo is one of the few places you can see a leatherback turtle
Leatherbacks can stretch to an extraordinary three metres in length. This one did not seem perturbed by our presence as we measured her and clipped on a tag. Gently but with heavy sighs and tears of salt water running down her cheeks she used her flippers to throw sand behind her. She did her best to hide the burial spot and then shuffled back to the sea.
It was a sight I will never forget.
From Our Own Correspondent was broadcast on Thursday 1 February, 2007 at 1100 GMT on BBC Radio 4. Please check the programme schedules for World Service transmission times.