The climate of Madagascar is influenced by the relief and tropical location of the island, and by the reversal of atmospheric circulation in the southwest Indian Ocean. Along the coastal lowlands average annual temperatures range from 27°C in the north and west to 23°C in the south and east. But in the central highlands the Tananarive-Fianarantsoa area has an average annual temperature of less than 18°C. The eastern coastlands receive rain virtually throughout the year from the southeast trade winds as they lift over the scarps, many sections having an annual rainfall of over 2,800 mm. The northwestern uplands have their heaviest rains in the December-March period, from the northerly monsoon and the intertropical convergence zone, the annual amount often exceeding 1,600 mm. But the central uplands around Tananarive are relatively dry with an average annual precipitation of about 1,000 mm. Dryness increases toward the southwest, where semi-arid conditions with less than 700 mm prevail.
Vegetation reflects the climatic contrasts and ranges from tropical rain forest on the eastern coastlands through tropophilous forest in the north central zone to drought resistant scrub in the southwest. But interference by man has been considerable and large areas in the interior have degenerated to tropical savanna.
About 85% of the population live in the rural areas; crops and cattle are the basis of the economy. The French encouraged the growing of commercial crops like coffee, cacao, sugar cane, vanilla, coconuts, sisal and cotton, sometimes as large-scale operations but also on the many small farms. Plantations were established, especially on the humid eastern coastlands, associated with subsistence crops of wet rice. Rice is the republic's basic food crop. In the drier south and west the cultivation of corn, potatoes, manioc, Cape peas and cotton has been maintained, along with livestock-rearing.
Though agriculture provides most of the republic's exports, it suffers from the deep-rooted conservatism of the Malagasy farmer, which has greatly hindered the spread of modern techniques.
Export crops such as coffee and sugar suffer from competition and price fluctuations in world markets, and from the ravages of the cyclones that sometimes hit the island between December and April.