The big mammals for which Africa is so famous are vanishing in staggering numbers. According to a study published last year: Africa's large mammal populations have dropped by 59% in just 40 years. But what is even more alarming was that the study only looked at mammal populations residing in parks and wildlife areas, i.e. lands that are, at least on paper, under governmental protection. Surveying 78 protected areas for 69 species, the study included global favorites such as the African elephant, giraffes, zebra, wildebeest, and even Africa's feline king, the lion.
"We weren’t surprised that populations had dropped but we were surprised by how large the drops had been," lead author Ian Craigie told mongabay.com in an interview. Craigie says that there are a number of causes behind the observed declines, including agriculture, hunting, and the bushmeat trade. But all of them are due to human actions. In fact, he points to Africa's population explosion as one of the underlying factors.
"In Africa man has successfully lived alongside large populations of wild animals for millennia but the advent of advanced technology and agriculture has lead to a 5-fold increase in African human populations since World War 2. All these extra humans are using and moving into previously natural habitats and squeezing out the wildlife," he says.
The study looked at three general regions across Africa: Southern African, East Africa, and West Africa. Wildlife in Southern African parks fared the best according to Craigie because "the level of funding for parks in Southern Africa is much greater than other regions" and the region has lower population densities. West Africa's parks came in last due to a culture of bushmeat hunting, poverty, and booming human populations. The overall decline of African mammals is likely to be worse than even the study portrays for two reasons: mammal populations have almost certainly suffered worse outside of parks than inside, and Craigie and his team were not able to include parks that didn't regularly survey their wildlife populations.
EDIT
http://news.mongabay.com/2011/0127-hance_craigie.html