Global history has changed a number of times due to agriculture. Different steps in the history of agriculture have had different impacts on the world.
Perhaps the biggest impact of agriculture came when it was invented. The invention of agriculture made civilization possible. Before agriculture was invented, all people were hunter-gatherers. They were almost all nomadic and their societies could not have large populations. Moreover, essentially no one could specialize in anything other than obtaining food. When agriculture was invented, this changed. Farmers could grow enough food to feed people other than themselves. This allowed larger populations to arise in established, permanent settlements. The people who did not need to farm could become government officials or artisans or other types of people who could make a whole civilization.
Later on, agriculture led to slavery in the New World. The Europeans started to grow sugar cane, tobacco, and eventually cotton. They needed slaves to do the work and, therefore, started the African slave trade.
In more recent times, the “Green Revolution” has helped to improve standards of living around the world. This revolution brought about plants that produced higher yields. These plants were made available in the Third World and made it possible for people there to have more food and better standards of living.
In these and many other ways, agriculture has had an impact on global history.