The park has acidic woodland, parkland, woods and ponds. It has the best ancient woodland invertebrates in the county, including the nationally rare beetle Platypus cylindrus and several nationally scarce species, and it also has a rich fungus flora.
Rye Meads is a 58.5 hectare biological Site of Special Scientific Interest (SSSI) in Rye House, Hertfordshire. It is also part of the Lea Valley RAMSAR site (a group of internationally important wetland sites) and a Special Protection Area. The SSSI is divided into three areas. North of Rye Road is the Rye Meads nature reserve, which is open to the public. The western half of this nature reserve, next to the River Lea in the Lee Valley Regional Park, is managed by the Royal Society for the Protection of Birds (RSPB). The eastern half is managed by the Hertfordshire and Middlesex Wildlife Trust (HMWT). The SSSI also includes a meadow and lagoons owned by Thames Water south of Rye Road which is not open to the public.
The RSPB reserve has ten birdwatching hides, trails and a visitor centre. Birds include kingfisher, snipe, green sandpiper, shoveler, gadwall and tufted duck.
The HMWT site is an ancient flood meadow which has a variety of habitats including reedbed, marshy grassland and fen. It is grazed by ponies and water buffalo.