Counting the species: how DNA barcoding is rewriting the book of life

We do not know how many species live on Earth. Barcoding could change that - and open the way for incredible discoveries

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Guanacaste conservation area in north-west Costa Rica is the most DNA barcoded place on Earth. On its western frontier, jaguars hunt turtles from the mangrove swamps that line the Pacific coast. Endangered spider monkeys swing through dry tropical forest, the remnants of a rapidly disappearing ecosystem that once ran from northern Mexico to Panama.