The watershed of the Toa river extends for , and has a half slope of . It takes up about 70% of the Cuchillas del Toa Biosphere Reserve. The area around the river is home to many species of endemic flora and fauna, including at least 1000 species of flowers and 145 species of ferns. Species in danger of extinction, such as the tocororo (which is also the national bird of Cuba) and the hook-billed kite, are also among the fauna of this area.