Here is a post based on Herdsmen and Farmers Crisis in Nigeria,

Cain was a Arable farmer while Abel was a Livestock farmer
Gen 4:2 And she again bare his brother Abel. And Abel was a keeper of sheep, but Cain was a tiller of the ground. I never read of any clash between them based on their work!
Abraham and Lot Herd's Men

Gen_13:2 And Abram was very rich in cattle, in silver, and in gold. Gen_13:5 And Lot also, which went with Abram, had flocks, and herds, and tents. Gen 13:7 And there was a strife between the herdmen of Abram's cattle and the herdmen of Lot's cattle: and the Canaanite and the Perizzite dwelled then in the land. Gen 13:8 And Abram said unto Lot, Let there be no strife, I pray thee, between me and thee, and between my herdmen and thy herdmen; for we be brethren. Their was disagreement between herd's men of Abraham and Lot. Not between herd's men and farmers!

Isaac's Herd's Men
Gen_26:20 And the herdmen of Gerar did strive with Isaac's herdmen, saying, The water is ours: and he called the name of the well Esek; because they strove with him. Disagreement between among the herd's men of Isaac and herd's men of Gerar. Not between herd's men and farmers!

Gen_32:7 Then Jacob was greatly afraid and distressed: and he divided the people that was with him, and the flocks, and herds, and the camels, into two bands;

Herd's Men
If Abraham, Isaac, Jacob etc could handle herd's men and farmers relationship in those day and we are not able to do so now, then some thing is wrong some where. The government should make sure herdsmen register with the local governments where they are located. If possible, register their cows like vehicles are registered. The government can even generate some income by issuing cow-license. Make ranches for them. If any is adamant and prefers to take his cows through the street, then let their me monthly cow-license!

There are many undergraduate project works, OND, HND, M.Sc. and Ph.D. dissertations and theses which explored the Nigerian Vegetation distribution. Get them for study. Identify grazing paths which do not pass through farm land. Organize seminars for them (Herdsmen and Farmers) in their languages to enlighten them about the paths. Do we need God to do all these for us?