Zanzibar have acute malnutrition. Life expectancy at birth is 57 years, which is significantly lower than the 2010 world average of 67.2. The general prevalence of HIV/AIDS in the population of Zanzibar aged 15–64 is 0.5 percent, with the rate much higher in females (0.9 percent) than males (less than 0.1 percent). Environment The northern part of the island presents elevated volumes of trash in the streets, beaches and the ocean—mostly plastic bottles, other plastics and cigarette butts. There is indiscriminate dumping in residential areas. Medical equipment waste is a particular problem on the island. Climate change impact Studies conducted show temperatures and wind speeds have increased strongly over the last 40 years. These climatic stressors, in addition to the changes in rainfall patterns have had significant effects on the seaweed farming, causing seaweed to rot or be destroyed in the process of yielding. Economy Ancient pottery implies trade routes with Zanzibar as far back as the time of the ancient Assyrians. Traders from the Arabian Peninsula, the Persian Gulf region of modern-day Iran (especially Shiraz), and west India probably visited Zanzibar as early as the 1st century. They used the monsoon winds to sail across the Indian Ocean to land at the sheltered harbor located on the site of present-day Zanzibar City. The clove, originating from the Moluccan Islands (today in Indonesia), was introduced in Zanzibar by the Omani sultans in the first half of the 19th century. Zanzibar, mainly Pemba Island, was once the world's leading clove producer, but annual clove sales have plummeted by 80 percent since the 1970s. Zanzibar's clove industry has been crippled by a fast-moving global market, international competition, and a hangover from Tanzania's failed experiment with socialism in the 1960s and 1970s, when the government controlled clove prices and exports. Zanzibar now ranks a distant third with Indonesia supplying 75 percent of the world's cloves compared to Zanzibar's 7 percent. Zanzibar exports spices, seaweed and fine raffia. Beside the Zanzibar State Trading Cooperation, Zanj Spice Limited, also known as 1001 Organic, is the biggest organic spice exporter in Zanzibar. Zanzibar also has a large fishing and dugout canoe production. Tourism is a major foreign currency earner. The Government of Zanzibar legalized foreign exchange bureaux on the islands before mainland Tanzania moved to do so. The effect was to increase the availability of consumer commodities. The government has also established a free port area,