Sumaco is isolated from the Cordillera Oriental by the lowland valley of the Cosanga and Quijos Rivers. There are more than 6000 species of vascular plants, including more than 90 endemic species. There are also a number of endemic animals, including toad Osornophryne sumacoensis only known from the eastern slopes of Sumaco, and robber frog Pristimantis ernesti only known from the summit of Sumaco.