Geography and Climate Nerd-Out Session!!!—All About Liberian Agriculture—Part 2

Liberia is located on the west coast of Africa just less than 500 miles north of the equator. It is bordered on the west by Sierra Leone, on the north by Guinea, on the east

Liberia sits on the west coast of Africa with the Saharan desert to the north and the Atlantic Ocean to the south.

Liberia sits on the west coast of Africa with the Saharan desert to the north and the Atlantic Ocean to the south.

by Côte d’Ivoire, and on the south by the Atlantic Ocean. The Saharan desert is well north of Liberia, but it still has an effect on the country’s weather and climate.

The total land area is about 24.2 million acres, half of which is tropical forest (Table 1). Tillable land, comprising of uplands (41%) and lowlands (6%) cover about 47% of the total land area. Liberia is almost cut in half with the uplands being considered the land area farthest away from the

Land use in Liberia

Land use in Liberia

coastline and the lowlands being the half of the country that starts at the coast and meets the uplands in the middle. Pasture land is about 450,000 acres.

The soils range from weakly developed muds and flooded, anaerobic clays along the coast and the inland swamps, to shallow soils on the plateaus and mountains.Liberia topo map

The topography comprises mainly flat rolling coastal plains running into some interior
plateaus, and then mountains in the north-eastern part of the country as can be seen in the map below. There are four distinct relief zones or belts parallel to the coast – the coastal plains (up to 100 m above sea level), rolling hills (100-300 m), plateaux (300-600 m), and northern highlands (in excess of 600 m).

Liberia has a tropical and humid climate. Throughout the year, temperatures stay hot, with high temperatures averaging between 78 degrees F and 88 degrees F. Monrovia TempsThere are two distinct seasons—a rainy season and a dry season. The rainy season starts in May and ends in October, whereas the dry season starts in November and ends in April. In Kakata, the city where we will be living, we expect to get about 120-140 inches of rainfall in a year’s time. Interestingly, Monrovia, lying on the coast about 1.5 hours away from Kakata, is well known as the wettest capital city in the world!Monrovia Rainfall

Here is where it really gets interesting to my fellow science nerds (don’t be afraid to admit it!). The rainy season (and dry season for that matter) is the result of the African monsoon—yeah you heard me right. We will be living through a monsoon! For further explanation of the Liberian weather I’ll give you two options: (1) monsoons and weather patterns for dummies; (2) Monsoon Nerd-out (you’ve been warned)!!

Option #1: Monsoons and Weather Patterns for the Laymen

Basically Liberia’s is in the middle of two bullies—the Saharan desert to the North, and the equatorial Atlantic Ocean to the south—which take turns winning their fight during the year. When the Saharan desert wins the fight (Dry season: November-April) Liberia has dry air moving through its land which produces very little rainfall, but brings with it a lot of dust and high winds. When the Atlantic Ocean wins (Rainy season: May-October), moisture-filled air comes up from the ocean and quite literally rains over the country…and it rains a lot. Right before the rainy season begins (March and April) are the hottest times of the year, sometimes exceeding 105 degrees F. It’s at this time that I will be hoping that my humid and sticky Maryland summers have prepared me for a dry 105!African monsoon map

Option #2: Monsoon Nerd-out!

Now bear with me as I nerd out in trying to explain how the monsoon comes about. All around the circumference of the earth, near the equator, prevailing and dominant winds converge head-on—a place that I will call the convergence zone (see map) from now on. The prevailing winds on the northern side of the convergence zone go from north east to south east, and on the southern side of the convergence zone, the prevailing winds go from south east to north east (the opposite). The convergence zone moves north of the equator when it is the northern hemisphere’s summer, and the convergence zone of these prevailing winds moves south when it is the southern hemisphere’s summer (Side note: if you wondering why it moves, it’s because the change in temperature throughout the year on land makes low pressure and high pressure zones between land and water, which causes movement because, as you already know, high pressure always wants to move to a lower pressure area). In the month of May, the convergence zone has moved north of Liberia, causing the prevailing wind to come from the southeast rather than the normal northeasterly wind. This wind coming from the southeast, and the Atlantic Ocean, brings moisture-filled air that gets heated up once it reaches land. Hot air will then do what we know it always to do—it rises. When it rises it gets cooled because of higher altitudes, and cool air has a much lower water holding capacity. Thus, it rains…and it rains….and it rains some more…until October. There is a lull in the rain in August because for a short time the rainy front moves north with the convergence zone, but it quickly makes its way back down through Liberia in September and October.

Conversely, when the convergence zone has moved south of Liberia (into the Atlantic Ocean), we will be experiencing the “normal” prevailing winds which are very dry and dusty because they are coming from the Saharan desert. From December to February, these Saharan desert prevailing winds turn it up a notch, and can be very strong. The temperatures in Liberia are at their highest in March and April, right before the convergence zone passes over and the rainy season begins. Temperature during this time can exceed 105 degrees F. It’s at this time that I will be hoping that my humid and sticky Maryland summers have prepared me for a dry 105!

Agro-ecological zones

Table 4 summarizes the land coverage, location and vegetation of the major agro-ecological zones (AEZ), and Figure 6 shows the main vegetation zones. Broadly, three main AEZ can be identified: 1) coastal plain or swamp, 2) forest, and 3) savannah. Each AEZ has its own unique vegetation determined by rainfall pattern, altitude, topography, temperature and human interference. Kakata, the city where we will be, fits into the upper high land agro-ecological zone from the table below, but is definitely not in a forest area. It is more like the “farm bush” zone which is the transition from coastal plains to closed forest.

 

AEZ Land coverage Counties Agro-Climate Vegetation and Farming Systems
Coastal Plains Commences from sea level and extends to a height of 30 masl inland as well as savannah up to 25 km into the interior of the country. Bomi, Cape Mount, Grand Bassa, Margibi and River Cess Very high levels of rainfall (4,450- 4,550mm), high humidity (85-95%), longer sunshine hours with high and wider temperature ranges Vegetation: swampy along rivers and creeks, mangroves, scattered patches of both low and high bushes and savannah woodland belt up to 25km inland.
Farming system: rice on upland and lowland, cassava intercropped with vegetables and sugarcane. Rubber, coffee and cocoa are cultivated. Grassland a potential pasture resource.
Upper Highland Tropical Forest (Agric. Belt) Composed of the plateau (tablelands) about 30m above sea level and mountain ranges (600m) behind rolling hills. Upper Cape Mount, Lofa, Bomi, Margibi, Bong, Grand Bassa, River Cess and most of Nimba Bi-modal rainfall (sub-divided by short dry spell of 2 weeks) more evenly spread of 2,900mm from Lofa to Nimba, 1,265mm in Bong and 3,200 maximum (overall). Temperature variation is 5 degrees Vegetation: closed semi-deciduous forest and transition zone or secondary forest (‘farmbush’).

Farming system: excellent for cocoa and coffee typical of Lofa, Bong and Nimba, as well as rubber, citrus and oil palm are the main cash crops. Upland and lowland rice in the forest (upper and lower region), plus yams, cocoyam, plantains, potatoes and vegetables.

Lower Tropical Forest Mid-altitude rolling hills composed of valleys, hills and numerous water courses. Sinoe, Maryland, Grand Kru, Grand Gedeh and parts of Nimba County Average rainfall from 3,000mm in Maryland to 4,100 mm in Sinoe. Long and dry spell and two distinct peaks of rainy seasons. Vegetation: mostly evergreen rainforest in south-eastern part of the affected counties.

Farming systems: upland and lowland rice cultivation in the forest (upper and lower regions), plus yams, cocoyam, plantains, potatoes and vegetables. Rubber, cocoa, coffee and sugarcane are the major cash crops.

Northern Savannah Northern Lofa and Northern Nimba High elevation with average rainfall between 700 mm -1,750 mm Vegetation: dense elephant grass (Pennisetum purpureum) of up to 1.5m, scattered trees and patches of forests. It consists of the derived and guinea savannahs which in addition to the coastal savannah are the main pastoral resources

Thanks for bearing with me as I nerded-out about Liberia’s climate and geography. Every part of this post goes into making agricultural decisions and teaching about an agricultural world that is very different than our own. Every part of this post will help us to understand the environment in which we will be living. Hope you learned a lot, just as I did. Stay tuned for part 3 of this 3-part post on Liberian agriculture where we take a more in-depth look at Liberia’s major crops. So long!

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