Table 1. List of Nigerian states where the study was conducted.

State	Agro-climate	Source	Human population ( NASS, 2011)
Bauchi	Spans Sudan savannah (south) and Sahel savannah (north) vegetation zones	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Bauchi_State.html	4,653,066
Kaduna	Sudan savannah type	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Kaduna/Kaduna_State.html	6,113,503
Kano	Tropical savannah	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Kano/Brief-History-of-Kano.html	9,401,288
Nasarawa	Tropical with moderate rainfall. Mainly agricultural land	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Nasarawa_State.html	1,869,377
Niger	Largest Nigerian state by land area	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Niger/Niger_State.html	3,954,772
Sokoto	In dry Sahel, surrounded by sandy savannah and isolated hills	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Sokoto/Sokoto_State.html	3,702,676
Zamfara	Tropical climate	https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Zamfara/Zamfara_State.html	3,278,873