in recent history numerous terrestrial mammals birds snakes and frogs can no longer survive in the wild in targe enough populations to ensure their continued existence on earth eg myers and others brooks and others in these categories the best available evidence indicates that a taxon is facing a high to extremely high risk of extinction in the wild a review revealed that globally there around marine species andor subpopulations on the red list that are categorised as threatened since we know considerably more about the diversity of life on land than in the sea eg pimm and others and even less about threats to marine life especially in the deep sea this figure is considered conservative it should also be noted that while the trend in general is unfortunately for species to move up the threat ladder for example from near threatened to extinct in the wild there are exceptions whereby species that were vulnerable have dropped to one of least concern because numbers or populations have increased and threats have reduced