The Biosphere Reserve situated in the east side of the Island is included in a perimeter limited northward by the city of Mananara North , westward by Sandrakatsy, southward by the river Anove and the village of the same name. The oriental limit follows the coast in background on 5km , from the village of Anove to North Mananara.
The National Park is divided in 2 distinct parts. The most important part that is situated in the « Great land » including various forests (Verezanatsoro, Ivontaka South, and Ivontaka North forests and that situated at the river Anove) represents an average area of 23 000 ha.
The second part , smaller, regroups the islands of Nosy Atafana (face to Sahasoa village ) and surrounding reefs . It represents 100 ha of marine park .With an altitude between 0 and 570 m, the Reserve is situated in a region composed by crystalline hills . A sand fringe borders the coast from Anove to Antanambe. Northward, beaches are rare and isolated. The steep coast faces reefs that strew the sea on near 200 m from littoral. The group of islands of Nosy Atafana present also a fringing submerged reef.

The climate is humid tropical type characterized by annual average precipitations of 3000 mm . Practically there is no dry season. (180 days of rain / year). The month of October is the most dry of the year with 101mm of precipitation . The humidity is continually high . Monthly average temperatures are between 19°C and 26°C

The vegetation is always green forest type of low altitude with at least two distinct unities :
- on coastal part : the sandy plain composed of a specific vegetation (Terminalia Catappa, Calophyllum sp., Canarium sp. And Heritiera sp.) with mangrove formation (Rhizophora Micronata and Avicennia marina)
- on laterit grounds : typical species are Weinmania, Tambourissa, Diospyros, Cryptocarya, Oncostemon, Dypsis and Crysalidocarpus. The Canopée is relatively high , it can reach until 40m high with an average of 30 – 35 m. Mananara North forests are renowned for their wealth in palm trees species . The region constitutes a rich enclave for the communities of eastern pluvial forests and coral reefs .

Among the 16 species of present reptiles : the Nile Crocodile (Crocodilus niloticis), Ithycyphus perineti and Chameleo cucullatus.
60 species of birds have been counted, some of them are rare or localized such the land Rollers (Agelastes squamiger and Brachypteracias leptosomus) or the Euryceros of prévost. It is the only protected area for the mammals Galidictis fasciata and Salanoia concolor. The lemurs are well represented with the Propithecus diadem, the Lemur vari, the Indri and the Aye Aye. The flat-nosed Hapalemur (Hapalemur simus) can exist in the South of the reserve as well as the Dugong dugon in the marine park area .