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Difficulty: Very hardAgricultural Systems, Crop Production, and Pastoralism in Nigeria

In evaluating agricultural systems and pastoral transhumance across Nigeria's latitudinal ecological zones, livestock herders in the northern Sudan and Sahel savannas routinely migrate southward toward the Guinea savanna and major river basins during the dry season, but return northward at the onset of the rainy season. Which of the following correctly identifies the primary environmental driver of this seasonal southward migration and the critical ecological constraint that necessitates their wet-season northward retreat?

  1. Dry-season migration is driven by acute pasture and water shortages in the northern savanna, while the wet-season retreat is necessitated by the proliferation of tsetse flies and trypanosomiasis risk in humid vegetation zones.Answer
  2. B
    Dry-season migration is driven by the harvesting labor demands of tree cash crops in the Sudan belt, while the wet-season retreat is necessitated by extensive salt flats flooding the Guinea savanna.
  3. C
    Dry-season migration is driven by the northward shift of the Inter-Tropical Discontinuity (ITD), while the wet-season retreat is necessitated by rapid soil salinization across the Benue Trough.
  4. D
    Dry-season migration is driven by severe crude oil contamination of northern rangelands, while the wet-season retreat is necessitated by extreme frost formation on the Jos Plateau.

Answer

Dry-season migration is driven by acute pasture and water shortages in the northern savanna, while the wet-season retreat is necessitated by the proliferation of tsetse flies and trypanosomiasis risk in humid vegetation zones.
The correct choice accurately reflects the ecological dynamics of transhumance in Nigeria: dry-season movement southward is driven by the search for water and pasture in the Guinea savanna and river valleys, while the wet-season movement back northward is driven by the need to avoid tsetse fly infestation (which causes trypanosomiasis in cattle) and crop land conflicts in humid southern zones.

Step-by-Step Solution

1
Identify dry-season environmental conditions in the far north of Nigeria.
The tropical continental air mass (Harmattan) brings prolonged drought, drying up streams and desiccating grasslands in the Sudan and Sahel savannas.
Faced with feed and water scarcity, pastoral Fulani herdsmen migrate southward toward wetter ecological belts (Guinea savanna and floodplains).
2
Identify wet-season environmental constraints in the middle and southern belts.
With the retreat of the dry season and arrival of the moisture-laden tropical maritime air mass, vegetation in the middle belt becomes dense and humid.
High humidity and thick foliage foster vector breeding grounds for tsetse flies (Glossina spp.), which transmit fatal nagana (trypanosomiasis) to cattle, forcing herdsmen back to drier northern zones.
3
Evaluate options against verified geographic distributions and ecological facts.
The option pairing northern dry-season pasture/water deficits with southern wet-season tsetse fly infestation correctly captures the dual mechanism of transhumance.
Distractors contain spatial misallocations, such as placing tree cash crops or crude oil fields in northern savanna zones.

Key Concept

Ecological controls of pastoral transhumance and crop zoning in Nigeria
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Topics

Agricultural Systems, Crop Production, and Pastoralism in Nigeria

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