to carry out trade along the Congo and Niger Rivers. They also made slavery illegal in the area. The Congo Free State was essentially declared the personal property of Leopold II.  

African nations were left completely out of the process of carving up Africa. The conference sparked increased European interest in Africa, and, by 1900, 90% of Africa was claimed by Europeans. The principle of "effective occupation" established at the conference meant that European powers had to physically establish control over areas to claim them, so the Europeans began to use force, if necessary, in their quest to gain new territories. The Congo Free State became the site of hideous crimes as Leopold II deputized forces to seize rubber, ivory, and other materials by terrorizing and brutalizing the local people. 

The main way in which the Berlin Conference of 1884-5 affected Africa was by chopping it up into areas that would be colonized by various European countries.  This had long-lasting effects on the continent.

Before the Berlin Conference, most of Africa was still in the hands of Africans.  Europeans had only colonized coastal areas.  However, this was changing.  At the conference, the European countries divided up essentially all of Africa.  They decided which European countries would get to own which parts of Africa.  This doomed the African continent to decades of colonization by European powers.

Colonization harmed Africa in two major ways.  First, colonial governments and economies were set up to help the Europeans, not the Africans.  The Europeans ran the colonial economies in ways that made money for the Europeans but did not enrich Africans and did not even train them to someday know how to do good jobs.  The colonial governments did not allow Africans to participate.  They did not really educate Africans.  This meant that when independence came, there were very few Africans with the education or the experience needed to set up their own modern governments.  These things helped make many African countries poor and chaotic after independence.

Secondly, the European governments simply divided Africa up however they wanted.  They did not take into account the human geography of Africa.  They divided up people of one ethnic group into different countries.  They made countries that had multiple ethnic groups, many of whom did not get along.  When these countries became independent, they ended up having ethnic conflicts, further weakening them.

The main effect of the Berlin Conference, then, was to colonize Africa, leading to many of the problems that the continent endures today.