Cuba's political and economic exile has yielded a startling upside: A pristine island preserve boasting one of the most diverse and primordial ecosystems in the region. But how will nature fare if the U.S. trade embargo ends and tourists pour in? This episode of the PBS series observes jumping crocodiles, painted snails and other famed residents while profiling the unsung scientists who are studying and protecting the creatures' idyllic habitats.

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