Large-mammal populations have declined across Africa

Across Africa, large-mammal populations suffered major declines in recent decades.

Herds of wildebeests and zebras and prides of lions still roam Africa's national parks, but they do so in smaller number, according to a study that found that large-mammal populations in those parks shrank an average of 59 percent over 35 years.

Researchers from the Zoological Society of London and Cambridge University collected animal census data from 78 protected areas in Africa, spanning the years from 1970 to 2005. They found that 69 species had experienced a drop-off in population. "I thought there would be one or two places that weren't doing so well," said Ian Craigie, primary author of the study, which was published in the July issue of the journal Biological Conservation, "but it's a problem across the entire continent."

In addition to wildebeests, zebras and lions, the researchers reported reductions in giraffe, buffalo, elephant and rhino populations.

Results differed regionally, however. East African populations declined about 52 percent. Those in the west declined about 85 percent by 2002; there was insufficient data for later years. But in southern Africa, the overall large-mammal population either maintained its size or grew. Researchers did not know why the southern populations fared better, but suggested that hunting and habitat destruction were likely reasons for overall decline.

Although their study did not include population trends for areas surrounding the national parks, the researchers said "however bad it is inside the protected areas, it is almost undoubtedly worse outside."

When he started this research, Craigie said, he thought he would be able to demonstrate the parks were doing a good job maintaining large mammals. But "even a tourist or a non-scientist can tell ... there are (fewer) of these animals."

The reasons for the population decline, Craigie said, are complicated but primarily "human-induced." Creating more national parks would not help much, he said, unless they were well-funded and well-managed.