NEW YORK — The oil slick in the Gulf of Mexico is now about the size of Puerto Rico. It's already reached the marshes of Louisiana. Oil-covered wildlife are starting to show up along the shores. Shrimp, fish and oyster harvest areas have been closed. Residents of Mississippi and Alabama are just waiting for the oil to hit. As environmental calamity for the Gulf Coast appears imminent, GlobalPost looks at 10 other man-made environmental disasters — both forgotten and infamous — that could have been prevented.

HAVANA, Cuba — In June 1961, Fidel Castro summoned Cuba’s leading writers and intellectuals to a meeting at Havana’s Biblioteca Nacional. There, he issued a warning that would regulate speech on the island for the next 50 years. “Within the Revolution, everything. Against the Revolution, nothing,” the 34-year-old Castro famously said. In other words, public criticism of Castro’s socialist system would be allowed — but only if its intent was to support the government, not oppose it.

CARACAS, Venezuela — As an opening salvo it was pretty innocuous. But Hugo Chavez has taken Twitter by storm, clocking up nearly 95,000 followers in the 36 hours since he sent his first message. Just weeks after declaring that sites such as Twitter channel “currents of conspiracy,” Chavez launched his own account on the digital telegram site that allows users to post messages with a 140-character limit.

Photo credit: Inauguration of the first Mobile Computer Laboratory at the Grenoble elementary school in the Quinta Normal district in Santiago, May 8, 2009. (Courtesy Enlaces, Education Ministry of Chile) SANTIAGO, Chile — Chile’s government spent years and more than $200 million putting computers and internet connections in almost every classroom of the country’s public schools. The kids were more than ready — but are the teachers?