Because Trinidad and Tobago lies on the continental shelf of South America, and in ancient times were physically connected to the South American mainland, its biological diversity is unlike that of most other Caribbean islands, and has much more in common with that of Venezuela. The main ecosystems are: coastal and marine (coral reefs, mangrove swamps, open ocean and seagrass beds); forest; freshwater (rivers and streams); karst; man-made ecosystems (agricultural land, freshwater dams, secondary forest); and savanna. On 1 August 1996, Trinidad and Tobago ratified the 1992 Rio Convention on Biological Diversity, and it has produced a biodiversity action plan and four reports describing the country's contribution to biodiversity conservation. These reports formally acknowledged the importance of biodiversity to the well-being of the country's people through provision of ecosystem services.