Paradise Archipelago in East of Indonesia

The archipelago around Sulawesi and Borneo has been described as an ecological 'hot spot'. East of Indonesia Archipelago have much terrain varied, from walls and fringing reef to caverns, big Green Turtles (Chelonia mydas), whitetip, leopard and nurse sharks, schooling barracudas, napoleon wrasses, cuttle fish, spanish mackerel, jacks and batfishes, and ornamentalreef fishes hang out in record densities and diversity.

If the sea has a heart, it lies somewhere in the dynamic mosaic that is the Indonesian archipelago. In this biological hot zone, there are more coral and fish species than anywhere else on Earth. The numbers are staggering: for instance, Indonesia has 83 species of angelfish and butterflyfish, while the whole of the Caribbean supports just seven of each.

This diversity is celebrated in The Sulu-Sulawesi Seas, a new photo-book by German photo-journalist Jürgen Freund. Part of a conservation initiative by the World Wide Fund for Nature (WWF), the book focuses on the area around Sulawesi, Borneo and the southern Philippines - the epicentre of the hot zone. This is a world where schools of jacks group into seething tornadoes over reef drop-offs, where tiny porcelain crabs seek refuge among the swaying tentacles of a host anemone. Stray from the reefs into a mangrove swamp and you are just as likely to run into a saltwater crocodile, the mightiest of the reptiles.

This region, referred to often as the 'coral triangle' or the 'East-Indies Triangle', encompasses three nations and an area of complex oceanography. All the islands have narrow continental shelves and many are separated from each other by relatively deep waters. Surface currents flow permanently eastwards along the north coast of Sulawesi and southwards along the west coast. To the south of the island there is a strong east-flowing current during the northeast monsoon, which is reversed during the southeast monsoon.

Conditions are ideal for reef development and there are fringing reefs along the shores of most of the smaller islands, and some continuous stretches running for hundreds of miles along the coastline. It doesn't take an expert to see that this is a special place: if you were to do a dive on a Sulawesi reef, then jet off to anywhere in, say, the tropical western Atlantic, the difference would be immediately noticeable. For years, photographers have said that the reefs of the Caribbean are like English gardens compared with the marine jungles of Southeast Asia.

For divers, it's down to the ease of finding certain exotic creatures. The highly cryptic leaf scorpionfish, for instance, can be found all over the Indo-Pacific, but in most places no one bothers to look over areas of exposed coral (their preferred habitat) for suspiciously leafy objects. When you're in the coral triangle, it's always worthwhile looking around for semi-disguised creatures. And if you're observant enough to find one leaf scorpionfish, there are usually others nearby.

Local dive operators are only too aware of the region's super-abundance of marine species. Log on to any website promoting diving in Borneo or Sulawesi and you will find phrases along the lines of 'located in the middle of the ocean's centre for biodiversity' or 'slap-bang in the middle of the ocean's Eden'. It's a strong selling-point, but can be misleading in terms of understanding the true nature of this magical place.

So, why are there so many different corals, fish and invertebrates in this region? Is it, as the websites suggest, some sort of underwater Eden? This has certainly been a popular theory, that the seas from Java to New Guinea represent an underwater 'cradle of evolution' from which all life in the shallow tropical seas originated. According to this approach, places such as Sulawesi have an abundance of species because it has been an evolutionary production line since since an early point in Earth's history. It's an attractive notion and has an appealing symmetry, not least because of parallel theories about the emergence of humans from Africa.

Unfortunately, the 'marine Eden' theory has a wealth of evidence stacked against it. If it is to be believed, all the coral in the world must have originated in and around Southeast Asia - but fossil research on Acropora corals shows that they originated around North Africa, Spain or even other parts of Europe, but not Indonesia. According to Dr Brian Rosen, a scientific associate in zoology at London's Natural History Museum, simple fossil data clearly shows that Southeast Asia was not a long-term cradle of coral development. 'If you look back 40 million years ago, Europe and the Caribbean were the major centres for coral reef diversity, and research in progress increasingly suggests that many reef organisms originated there,' Rosen explained.

So, between about five and seven million years ago, Europe's reef-building coral died out and the Caribbean's managed to stagger along, but by then Southeast Asia had become the hot zone. Rosen maintains that this was not due to any single cataclysmic event, but a long-term series of events which had made it the most attractive option for marine life.

'When environmental conditions change, organisms will go extinct if they cannot cope with the new conditions, stay where they are if they can cope, or if the change is not too drastic or too quick, they will gradually migrate into other regions where conditions are more suitable for them.' Put simply, if life has time to get out, it will do so while the getting out's good.

Most of the conditions and habitats that are found in present-day Indonesia also occur in the Caribbean - so why are there such differences in biodiversity? Dr Rosen - whose study of the issue amounts to a life's work - points out that if the environments are so similar today, then there must be long-term historical issues behind the development of the East Indies triangle.

So, let's look to history. It has been estimated that biodiversity may have accumulated in this region at the same time that extinctions were occurring in other parts of the world during the Pleistocene period (the time in our Earth's history from approximately 1.8 million years ago until about 10,000 year ago). The region is a labyrinth of volcanoes and deep basins that survived the Ice Ages, possibly providing a refuge for numerous species.

At the same time, the massive fluctuations in sea level may have isolated pockets of reef diversity, allowing evolution to follow different paths. When the species were reunited as sea levels rose, they had changed in many subtle - and not so subtle - ways, further adding to their diversity. The tortuous geography of the area has helped to create what Dr Rosen describes as a 'dynamic mosaic' which acts with variations in sea level to create a sort of 'diversity pump'.

Today, the triangle straddles an area in which two great oceans - the Pacific and the Indian - meet. That species from the two oceans come together and mix here is beyond contention. It is simply another of many factors that promoted diversity in the coral triangle. Ask any diver who has seen the currents ripping through Nusa Tenggara, the islands south of Sulawesi which include the famous Komodo Marine Park. It is here that the Pacific flows into the Indian Ocean, a vast movement of water impeded only by a few volcanic islands, around which some of the fastest currents on Earth occur.

Diverse as they may be, the reefs of the coral triangle face an uncertain future. Some 82 per cent of them are estimated to be threatened by human activities in the recent Reefs at Risk report. Human populations are over-using the resources in many areas, while rapid industrialisation and the continuing destruction of the forests on land are causing massive amounts of sediment and pollution to accumulate on reefs. The other major factor is global warming, widely believed to be underlying cause of coral bleaching.

Marine biologist Dr Alexander Mustard is another prominent diver and underwater photographer who has fallen in love with the coral triangle. He maintains that the preservation of Indonesia's marine environment is crucial not just for the region, but for the entire world. 'Anyone who has dived extensively in Indonesia will have seen the impact of dynamite fishing,' he said. 'If you're underwater and an explosion takes place within a few miles, you will literally feel the impact, despite the fact that dynamite fishing has been illegal in Indonesia since 1985.

'Even with the increasing population, there is more than enough protein in the sea to provide for human needs. But instead of harvesting it in a sustainable manner, they are destroying the very environment that supports the life. It's like being an orange farmer and, instead of picking oranges, you chop down the whole tree.'

Yet Jürgen Freund, whose pictures illustrate this article, feels there is still hope for the coral triangle. 'Some fishing communities now actively protect their fishing grounds and coral reefs, and others have mangrove reforestation programs,' he said. 'Once given a chance, the sea can replenish itself. In the Sulawesi Sea northwest of Manado, fishermen can pull a ton of tuna from the sea in two hours, using only simple bamboo fishing rods and small hooks. They could easily take more, but they have a simple philosophy - why take so much when we can keep some fish in the sea for tomorrow?'