The Federal Republic of Nigeria occupies a total area of 923 768 km2 between latitudes 4°15' N (the southern tip of the Niger delta on the Atlantic ocean) and 13°55' N (the north-western frontier with Niger) and between longitudes 2°45' E (the southern frontier with Benin) and 14°40' E (the northern frontier with Cameroon). The straight-line distances corresponding to the latitude and longitude are, respectively, approximately 1 050 and 1 300 km. The general relief is that of a plateau culminating in the central northern part of the country (Jos region) and divided into three parts south-west, south-east and north by the Niger River and its main tributary, the Benue. Mountainous ranges, some of them culminating at more than 2 000 meters, border the central and northern sections of the frontier with Cameroon.
The vegetation of Nigeria is determined by climate, in particular by the rainfall and the severity of the dry season. Farming, fires and soil also profoundly affect it. The following main vegetation zones can be distinguished:
- The forest zone (mangrove forest and coastal vegetation, freshwater swamp forest and lowland rain forest), a belt 50 to 250 km wide along the coast corresponding to rainfall generally higher than 1 600 mm, exceeding 2 500 mm in the delta and along the eastern coast (3 600 mm, for instance, at Forcados in the delta);
- The derived savanna zone with a 1 150 to 1 500 mm rainfall and a 3-months dry season, bordering the forest zone on the north;
- The savanna zones, including:
- The median and northern Guinea zones (1 000 to 1 250 mm, 5 to 6 months dry season);
- The Sudan zone (500 to 1 500 mm, 5 to 7 months dry season), which can be subdivided in a northern, median and southern Sudan zones;
- The Sahel zone (250 to 500 mm, 7 to 8 months dry season).
The savanna zones extend in this order from south to north, with the Sahel zone covering only approximately 1% of the total area of the country along the north-eastern border with Niger.
Altitude is a dominant factor for vegetation only on higher elevations of the Bauchi plateau and in the mountainous area along the central section of the Cameroon border.
Most of Nigeria has a tropical climate with warm temperatures throughout the year. The north is generally hotter and drier than the south. The average annual temperature in the north is about 29° C, but daily temperatures may rise above 38° C. The average annual temperature in the south is about 27 °C.
Precipitation is greatest in the south. The coastal areas average about 3 800 mm per year. Parts of the north receive only about 650 mm. The rainy season lasts from April to October in most parts of Nigeria, though it can last for a longer period of time in the south.
The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.