why do nomadic herders move their livestock from place to place
Nomadic pastoralism Nomadic pastoralism is a form of pastoralism when livestock are herded in order to find fresh pastures on which to graze. Strictly speaking, true nomads follow an irregular pattern of movement, in contrast with transhumance where seasonal pastures are fixed.[1] However this distinction is often not observed and the term nomad used for both—in historical cases the regularity of movements is often unknown in any case. The herded livestock include cattle, yaks, sheep, goats, reindeer, horses, donkeys or camels, or mixtures of species. Nomadic pastoralism is commonly practised in regions with little arable land, typically in the developing world, especially in the steppe lands north of the agricultural zone of Eurasia.[2] Of the estimated 30–40 million nomadic pastoralists worldwide, most are found in central Asia and the Sahel region of West Africa. Increasing numbers of stock may lead to overgrazing of the area and desertification if lands are not allowed to fully recover between one grazing period and the next. Increased enclosure and fencing of land has reduced the amount of land available for this practice. There is substantive uncertainty over the extent to which the various causes for degradation affect grassland. Different causes have been identified which include overgrazing, mining, agricultural reclamation, pests and rodents, soil properties, tectonic activity, and climate change.[3] Simultaneously, it is maintained that some, such as overgrazing and overstocking, may be overstated while others, such as climate change, mining and agricultural reclamation, may be under reported. In this context, there is also uncertainty as to the long term effect of human behavior on the grassland as compared to non-biotic factors.[4]
Cattle drives in the United States The first large-scale effort to drive cattle from Texas to the nearest railhead for shipment to Chicago occurred in 1866, when many Texas ranchers banded together to drive their cattle to the closest point that railroad tracks reached, which at that time was Sedalia, Missouri. However, farmers in eastern Kansas, still concerned that transient animals would trample crops and transmit cattle fever to local cattle, formed groups that threatened to beat or shoot cattlemen found on their lands. Therefore, the 1866 drive failed to reach the railroad and the cattle herds were sold for low prices.[10] There were other drives northward without a definite destination and without much financial success. Cattle were also driven to the old but limited New Orleans market, following mostly well-established trails to the wharves of Shreveport and Jefferson, Texas. In 1868, David Morrill Poor, a former Confederate officer from San Antonio, drove 1,100 cattle from east of San Angelo into Mexico over the Chihuahua Trail. This event, the "Great Chihuahua Cattle Drive," was the largest cattle drive attempted over that trail up to that time, but the market was much better in Kansas than in Mexico, so most drives headed north.[11]