Ian Burnet has asked me to post the Prologue of his new book Where Australia Collides with Asia: The epic voyages of Joseph Banks, Charles Darwin, Alfred Russel Wallace and the origin of ‘The Origin of Species’ so here it is:
The volcanoes of Mount Agung on Bali and Mount Rinjani on Lombok, their 3000 metre peaks shrouded in cloud, stand like giant sentinels guarding the northern entrance to the Lombok Strait which separates the Indonesian islands of Bali and Lombok. The strait is only 25 kilometres wide but it plunges to a depth of 2140 metres below sea level. Crossing the strait can be hazardous and its turbulent waters are the result of a major flowthrough of water between the Pacific and Indian Oceans.
In June 1856 the English naturalist Alfred Russel Wallace crossed the narrow strait between the two islands. During the few days when he stayed on the north coast of Bali he saw several birds highly characteristic of Asian ornithology of which he was already familiar and would expect to see the same birds as soon as he crossed the Lombok Strait. After a turbulent crossing and being dumped on the shores of Lombok he never saw the same birds again. He found a totally different set of species, most of which were entirely unknown not only in Java, but also in Borneo and Sumatra. Among the commonest birds he found in Lombok were white cockatoos and honeyeaters which are characteristic of Australia and are entirely absent from the western region of the archipelago. Wallace wrote in his book The Malay Archipelago:
The great contrast between the two divisions of the Archipelago is nowhere so abruptly exhibited as on passing from the island of Bali to that of Lombok, where the two regions are in closest proximity ... The strait is here fifteen miles wide, so that we may pass in two hours from one great division of the earth to another, differing as essentially in their animal life as Europe does from America.
As a consequence of the lowering of sea levels during the various Ice Ages, the main Indonesian islands of Sumatra, Java and Borneo were connected by dry land and it was the deep Lombok Strait which separates these larger islands sitting on the Asian Continental Shelf from the smaller islands of the eastern archipelago. The Lombok Strait represents part of the biogeographical boundary between the fauna of Asia and those of Australasia which was subsequently named the Wallace Line.
On the Asian side of the Wallace Line are the Asian elephant, the rare Javanese rhinoceros, Sumatran tigers and Borneo leopards, all kinds of monkeys, the orang-utans of Sumatra and Borneo, and numerous birds that are specific to Asia. On the Australasian side are the marsupials such as the possum-like cuscus and the tree kangaroos, as well as birds specific to Australasia such as white cockatoos, honeyeaters, brush turkeys and the spectacular Birds of Paradise. By his observations Alfred Russel Wallace had made a major contribution to a new science, the science of biogeography, or of the relationship between zoology and geography.
The great arc of the Indonesian Archipelago starts north of the island of Sumatra and curves south, east and north until it reaches Papua New Guinea. This arc of islands is defined by a string of active volcanoes in Sumatra, Java, Bali, Lombok, Sumbawa and Flores that erupt as the Australian oceanic plate is subducted under the island arc. Further east the island arc has been pushed to the north and then to the west by the Australian Continent which has been relentlessly marching northward since it separated from Antarctica 50 million years ago. Papua-New Guinea is part of the Australian continent and this journey north slowed about 20 million years ago when Papua-New Guinea collided with the Pacific Ocean Plate. The huge Pacific Ocean plate is moving westward and the resulting collision rafted segments of Papua-New Guinea, hundreds of kilometres towards the west and pushed the Indonesian island arc back upon itself. The tectonic stress caused by the continuing collision of Papua-New Guinea with the Pacific Ocean Plate has thrust the Papuan-New Guinea mountains up to a height of 5000 metres above sea level, where a tropical glacier still exists only four degrees south of the equator.
Eastern Indonesia represents a unique part of the earth’s surface, because it is here that four of the earth’s great tectonic plates - the Eurasian Plate, the Australian Plate, the Philippines Plate and the Pacific Ocean Plate are in collision with each other. Three million years ago in the region of Maluku (the Moluccas), these powerful forces fused together volcanic island arcs, continental fragments sheared off from Papua-New Guinea, seafloor sediments and coral reefs to create new land, forming the unusually shaped islands of Sulawesi and Halmahera. A subduction zone then formed along the western side of Halmahera, causing volcanoes to erupt out of the sea and spreading a thick layer of volcanic ash across the adjacent islands.
Nature abhors a vacuum, and the rich volcanic soils of these newly emergent islands were quickly populated by coconut trees grown from coconuts washed up on these shores, by plants whose seeds blew with the winds, by birds and butterflies able to fly from island to island, and by animals and insects drifting on floating trees and branches. Tropical temperatures and monsoonal rains provided the environment for a diversity of plant, bird and other animal species to thrive and evolve in unique ways. The profusion of islands allowed for a separation in the evolution of different species and became an ideal natural laboratory for scientific study. Alfred Russel Wallace spent five years exploring the tropical forests of Maluku, collecting and studying the birds, butterflies, insects and other animal life of eastern Indonesia.
It was ‘continental drift’ that brought these disparate worlds together and in this book we will follow the voyage of Continent Australia after its separation from Antarctica until its collision with Asia, thus creating the biogeographic region first observed by Alfred Russel Wallace and named as Wallacea in his honour.
It was my research into Wallacea and its unique position in the natural world that led me to write about the connections between the epic voyages of Natural History taken by Joseph Banks, Charles Darwin and then Alfred Russel Wallace. Here we follow ‘The Voyage of the Endeavour’ on its voyage around the world, which brought Joseph Banks and Daniel Solander to the shores of Botany Bay, where they became the first naturalists to describe the unique flora and fauna of the Australian continent. We follow ‘The Voyage of the Beagle’ on its voyage around the world, which brought the young naturalist Charles Darwin to South America and the Galapagos Islands before reaching Australia, where he sat on the banks of the Cox’s River in New South Wales and began trying to understand the significance of his discoveries. We follow Alfred Russel Wallace when he crosses the narrow strait between the islands of Bali and Lombok, we follow him on his ‘Voyage to the Aru Islands’ in search of Birds of Paradise and his recognition of the significance of the Australian marsupials he found there. And we follow the famous ‘Letter from Ternate’ that Alfred Russel Wallace wrote to Charles Darwin in February 1858, which forced Darwin to finally publish his landmark work On the Origin of Species.