Southern Guyana is host to some of the most pristine expanses of evergreen forests in the northern part of South America. Most of the forests found are tall, evergreen hill-land and lower montane forests, with large expanses of flooded forest along major rivers. Thanks to the very low human population density of the area, most of these forests are still intact. The Smithsonian Institution has identified nearly 2,700 species of plants from this region, representing 239 distinct families, and there are certainly additional species still to be recorded. The diversity of plants supports diverse animal life, recently documented by a biological survey organised by Conservation International. The reportedly clean, unpolluted waters of the Essequibo watershed support a remarkable diversity of fish and aquatic invertebrates, and are home to giant otters, capybaras, and several species of caimans.