The most important consequences of the Boer Wars for world history are the fact that the Union of South Africa was created largely as a result of this war and the fact that the Union was created as a white man's country with the beginnings of the apartheid system.
In the peace agreement that ended the wars, the Boers were to be given the right to self-government. These governments were to be set up before any discussion of black rights would be had. This meant that the Boers could set up their own forms of government without any input from the native South Africans.
By creating the Union of South Africa in these circumstances, the Boer Wars helped to create the situation that led to the creation of apartheid.