Their commitment was only to maintain the extent of forests, not their biodiversity.他们仅承诺维持现有森林面积，并不保证林区生物的多样性。The United States didn't affix its signature to the biodiversity treaty.美国没有在生物多样性条约上签字。If we don't protect biodiversity, we threaten the survival of the planet.如果我们不保护生物多样性，就会对地球的生存造成威胁。