Situated in the province of Tulear, at 85 km in the south of the city, the reserve is within a region composed of a calcareous plateau covered of thorny bush , the Mahafaly plateau and of the lake Tsimannampetsotsa localized at the sandy coastal plain of the Mahafaly.. With its banks, the escarpment and the Mahafaly plateau eastward , Tsimanampetsotsa is one the most beautiful southern sites of Madagascar to visit without forgeting to bring water as it is extremely rare in the region.
There is practically no permanent waterway, but soft water lakes in the plateau swallowholes . These give birth to soft water sources which become briny when in contact with the lake Tsimanampetsotsa waters .

Weak annual pluviometry (350 mm) and annual average temperature around 24° C.

The vegetation here is Malagasy sub arid thorny bush type .
However, the forest fringe comprised between the lake and the cliff (plateau Mahafaly)is composed of trees of 12m high as Cassia meridionalis, Cassia viguierella -Cesalpiniaceae , Ficus marmorata –Moraceae ... the edges of the lake are covered of halophyll vegetation constituted by Cyperus sp. Cyperaceae, and Salicornia pachystachia–Chenopodiaceae. A transect of 500m long on 2m width realized between the lake bank and the cliff of the plateau Mahafaly has underlined the presence of 36 woody species. As in the southern area, the specific diversity is weak , but the endemism is well marked as the formation of Pachypodium geayi and Adansonia fony that make the originality of this vegetation. The presence of Alluaudia montaniacii is also localized . A forest « gallery » with some great trees edge the Southeast bank of the lake .

The vertebrate fauna of Tsimanampetsotsa Reserve counts many species which distribution is limited to the sub arid south and some endemic species at this precise sector.
The particularly poor ichtyofauna in this sector is however represented by a cavernicole type , the blind Typhleotris madagascariensis which is localized in caves of the calcareous plateau between Tsimanampetsotsa and Itampolo and counted to a reduced number .
Waters of the lake Tsimanampetsotsa because of their chemical composition shelters no fish specie . Among reptiles, Pyxis arachnoides and Geochelone radiata are represented there. Its waters are poor and bit frequented by water birds even if some hundred of flamingos can be sometimes met there . A small shore bird , the Gravelot of Madagascar, nests on its banks.
Eleven species of mammals have been counted, among which one carnivorous specie ,Galidictis grandidiensis, known as being specific to the region of Tsimanampetsotsa, and 3 species of lemurs among which the lemur catta represented in great number in the region.