ZANZIBAR, Tanzania -- Said Ola began training early for the tourist trade in Zanzibar. As a youth he would come down to a popular park overlooking the Indian Ocean, one of the young men known as "practice boys" who learn English by chatting with visitors.
Mr. Ola used the English he picked up to work as a taxi driver and tour guide for the throngs who flock to the island each summer to snorkel among the coral reefs, explore spice plantations and wander through the ruins from the bygone days when Zanzibar was the capital of an Omani sultanate.
Like the rest of the dozen or so tour guides gathered recently at the edge of the park in historic Stone Town, Mr. Ola refused to believe that a local resident could have been behind the acid attack last month on two 18-year-old British girls, an episode that has brought unwelcome scrutiny to an island better known as a vacation paradise.
"We're not that stupid," Mr. Ola said, referring to the islanders' dependence on tourist revenues. Without the sightseers and beachgoers who throng the island, he said, "at the end of the day we're going to eat grass."
Ali Abdul Kareem, another guide, agreed. "This is our life," he said. "We depend on tourism." Murmurs of assent rippled through the group.
"If we knew who it was," said another, "we would be the first to punish them."
Zanzibaris worry that the acid attack will be declared a case of Islamist extremism and that the island, overwhelmingly Muslim, will be branded hostile territory to Westerners. The assault reinforced fears that stretch back to the discovery that one of the men behind the 1998 bombing of the United States Embassy in Dar es Salaam, Tanzania's largest city, was from Pemba, the smaller of the main two islands that make up Zanzibar.
In recent years, a group called Uamsho, or "Awakening," has called for an independent Zanzibar governed under Shariah law. Christian churches in Zanzibar have been burned and priests have been attacked in the past two years; one of them was killed. On the mainland, a radical cleric, Sheik Ponda Issa Ponda, was arrested for inciting unrest shortly after the attack against the British women. He was shot as the police apprehended him.
On Zanzibar, sunburned tourists in tank tops and shorts mingle with women shrouded in black abayas. In Stone Town, visitors consume alcohol mostly in rooftop restaurants and hotel bars known for their sunset views, but also strategically out of sight for pious locals. There have been attacks in the past against the small bars serving local neighborhoods, but the tourist haunts, and the tourists themselves, were always off limits.
"It was a shock, to be honest," said Ismail Jussa, a sixth-generation Zanzibari who represents Stone Town in the Zanzibar House of Representatives. "Never before had a foreigner been involved in such an incident."
Zanzibar, situated in the middle of Indian Ocean shipping routes, attracted Africans, Persians and Arabs to its coasts for centuries. The Portuguese, the Omanis and the British ruled the islands successively before Zanzibar achieved independence in 1963. The next year, the island entered into a union with mainland Tanganyika. (The name Tanzania is a portmanteau of Tanganyika and Zanzibar.)
The push for independence, or at least greater autonomy from the mainland, gained new impetus after politicians and jurists began work last year on a new constitution. At first, the status of the union was off the table, enraging Zanzibari nationalists.
"When the constitutional review process started, Zanzibaris thought, 'This is the right time to have this devil to rest,' " said Mr. Jussa, who said he favors a Zanzibar with its own currency, a seat at the United Nations and an Olympic team, but a common defense and security policy with the mainland. "The more you keep suppressing this issue, the more anger builds in the younger generation."
Many residents say that with the right leadership, an independent Zanzibar could develop into a model for East Africa -- a Singapore, Hong Kong or Dubai. Young people lament the lack of manufacturing jobs and other opportunities outside of tourism. They say the hotels take a greater share of the revenues and that better-trained outsiders from Kenya or Uganda get the best jobs.
"They feel that when we are in autonomy as Zanzibar their wealth can rise and there will be many jobs," said Muhiddin Zubeir, the executive secretary of the Zanzibar Imams Association. But mainland politicians, he argued, "don't want Zanzibar to be free."
The Rev. Cosmas A. Shayo, who came to Zanzibar in 1976 and was ordained as a Roman Catholic priest the next year, said that in the days of one-party rule few people in Zanzibar differentiated between local residents and those on the mainland, where Muslims are a minority. That changed as multiparty reforms began in 1992, and the distinctions have only deepened.
"The way Muslims talk about it in public rallies, they're speaking openly against Christianity," said Father Shayo, now parish priest of St. Joseph's Catholic Cathedral in Stone Town. Some people think "getting rid of the priests and bishops will get rid of the union," he said.
Two churches were set ablaze in May 2012 in the midst of rioting after the police arrested leaders of the separatist group Uamsho. On Christmas Day last year, a priest was shot in the jaw but survived. Another priest, the Rev. Evaristus Mushi, was shot and killed on Feb. 17.
During a recent Sunday service in Swahili at St. Joseph's, young men stood outside keeping watch over strangers. "Add up all of these things and there's something," said Father Shayo. "It could be religiously motivated. It can even be political."
But the troubles in Zanzibar had not attracted much attention beyond Tanzania until the attack on Aug. 7 against the two young teaching volunteers from London. Two men on a moped doused the teenagers with acid as they walked in Stone Town, severely burning their faces, chests and hands. The men reportedly smiled before speeding off.
Abdulsamad Ahmed, chairman of the Zanzibar Association of Tourism Investors, received a call shortly after the attack and rushed to the hotel where the young women had been taken. He said that as an individual he was chilled by the cruelty. As a businessman, he was terrified of the consequences.
While most of his family sought opportunities abroad in the Middle East, Britain and Canada, Mr. Ahmed began renting rooms in the family's three-story stone building in 1995 to backpackers for as little as $5 a night. He invested his earnings in a beachside resort, which opened in 1998 with six thatched huts but no electricity or running water. His resort now has 70 rooms, with air-conditioning and Internet service.
The association says tourism officially accounts for a little more than a quarter of the island's economic activity, but 70 percent of its foreign-exchange earnings. Fifteen thousand people work directly in tourism, and 50,000 are employed indirectly -- as money-changers, artists painting in the traditional Tinga Tinga style or fishermen whose catch ends up at hotel restaurants.
Like many Zanzibaris, Mr. Ahmed was unwilling to accept that rising extremism could be to blame, saying he believed the attack was personal. "It's not religious persecution, not Muslims don't like Christians," he said.
The guides in the park theorized that a conspiracy to drive tourists away from Zanzibar could have been hatched by competitors on the Kenyan coast, or by mainland Tanzanians to derail independence efforts.
"This issue could be based in politics, how to wound the image of Zanzibar," Mr. Ola said. "If you want to control people, let them suffer," he said. "That's what's happening."
This article originally appeared in The New York Times.