226 climate and geography: Asia and the Pacific (304–30 b.c.e.), the Greek dynasty that ruled Egypt after the conquests of Alexander the Great, and then by the Romans It became as important as the Silk Road for the transfer of goods and ideas between East and West In the early Middle Ages control of this trade passed to the East African state of Axum in Ethiopia, but by the ninth century, with much of the Indian Ocean coast in Islamic hands, the monsoon trade was monopolized by Arab merchants (who greatly improved its efficiency through the invention of modern sails and riggings on their ships) After losing this trade, the empire of Axum quickly collapsed The great European trading states such as Portugal, Genoa, and Venice were highly dissatisfied with the Arab monopoly, because the high fees and taxes charged by Arab merchants and governments cut into their profits when they transshipped Indian and other oriental goods across the Mediterranean This condition was made worse as the breakup of the Mongol Empire in the late 14th and 15th centuries disrupted trade along the Silk Road An effort to break the Arab stranglehold on Far Eastern trade was behind the efforts of the European trading powers to find other sea routes to India and China Their explorations led to such discoveries as those of Vasco de Gama (who rounded the horn of Africa in 1497–98) and Christopher Columbus (who discovered America in 1492 while trying to reach the Orient) and to Ferdinand Magellan’s circumnavigation of the globe (1519–22) Southeast Asia Southeast Asia consists of a large peninsula south of eastern China and the numerous nearby islands of the Indonesian and Philippine archipelagos This includes the territory of the modern states of Myanmar (Burma), Thailand, Laos, Vietnam, Cambodia, Malaysia, Indonesia, and the Philippines as well as a number of smaller polities like the Sultanate of Brunei on the island of Borneo The region is separated from southern China by high mountains ranges that to the south give way to several broad, flat river valleys From west to east the principal rivers (most of which have their sources in the Himalayas) are the Irrawaddy, Salween, the Chao Phraya, and the Mekong The region has a tropical monsoon climate (much wetter than India, with the rainy season lasting from May to October) and was originally covered in rain forest, with mangrove swamps in the lower elevations and bamboo forests in the mountains The area has a long history of rice farming, however, and in the Middle Ages the conversion of forest to cultivated land quickly accelerated The Indonesian archipelago consists of more than 13,000 islands, including five large ones: (from west to east) Sumatra, Java, Borneo, Sulawesi, and New Guinea New Guinea and Borneo are the second- and third-largest islands in the world, respectively Located directly on the equator, they are extremely mountainous, with many peaks above 10,000 feet and more than 150 active volcanoes and frequent major earthquakes In the ninth century c.e the Mataram kingdom had to build a new capital after its former royal residence was destroyed in a volcanic eruption The Philippine archipelago to the northeast of Indonesia consists of another roughly 7,000 volcanic islands (Luzon and Mindanao being the largest), equally mountainous and sharing the tropical monsoon climate of the area One of the most expansive states in medieval Southeast Asia was the Khmer Empire Begun about 800 c.e., it reached its height in the early 13th century (controlling much of modern Thailand, Cambodia, Laos, and Vietnam) and was overthrown by 1431 Like any organized imperial state, it depended on wealth from large agricultural surpluses Rainfall was sufficient to sustain a rich production of rice agriculture in the region throughout the Middle Ages, but the complex irrigation system also needed to grow rice was neglected because the empire tended to devolve into civil war The collapse of the system for managing the climate for agriculture led eventually to the collapse of the state Australia Southwest of Asia is Australia, the second-smallest continent It extends over more than 4.5 million square miles Most of Australia is a desert, with nearly half of the continent covered by sand dunes The northern fringe is rain forest and is subject to the same tropical monsoon climate system as Southeast Asia The eastern and southern coasts, separated from the rest of the continent by the Great Dividing Range (whose highest peaks are only about 6,500 feet), enjoy a more temperate climate with abundant rainfall The world’s largest coral reef, the Great Barrier Reef, lies off the east coast of Australia Hunter-gathers from Asia either crossed then-extant land bridges from Asia or made short sea voyages to occupy Australia about 45,000 years ago These were the ancestors of the current Aborigine population, and the character and development of their culture were only minimally disturbed by outside influence (sporadic trade with island Southeast Asia) until Europeans arrived in Australia well after the medieval period (ca 1600 c.e.) Although they possessed only the simplest technology and did not practice agriculture, the Aborigines may well have had a tremendous impact on the climate of Australia By introducing campfires, they probably started grass and forest fires at a much faster rate than the fragile forest ecosystem that existed then could absorb, resulting in the deforestation and desertification of much of the continent