The two main visual elements of this cartoon are the outline of Africa and the big old footprint over it. I think this cartoon is meant to symbolize how Africa has been treated, for example it looks like the Europeans came in and trampled and ruined Africa. The land under the boot print looks all infertile and cracked, just like Africa's economy and environment after the Europeans colonized most of Africa. it looks like the cartoonist feels that the Europeans "stepped all over Africa" and damaged it. He most likely has a negative opinion on imperialism. Another way he could have enhanced his message about colonialism, is he could have put images of suffering African people under the footprint or he could have shown cracks or Africa shattering.