African national parks like Masai Mara and the Serengeti have seen populations of large mammals decline by up to 59 per cent, according to a study published in Biological Conservation.

The parks are each visited by thousands of tourists each year hoping to spot Africa's 'Big Five' -- lion, elephant, buffalo, leopard and rhino -- but the research shows that urgent efforts are needed to secure the future of the parks and their role in tourism.

Scientists from the Zoological Society of London (ZSL) and Cambridge University created an index of change in population abundance for a multitude of species in 78 protected areas throughout Africa.

The index revealed an average decline of almost 60 per cent in the population abundance of 69 key species including lion, wildebeest, giraffe, buffalo and zebra between 1970 and 2005 in the national parks visited by millions of tourists each year. There is great variation by region with populations increasing in southern Africa, declining by more than half in East Africa and 85 percent declines in West Africa. The massive declines in West Africa are likely due to the lack of financial and personnel resources, high rates of habitat degradation and the growing bushmeat trade.

Despite the severe losses, the rate of decline has slowed over time, indicating that management of the areas has been gradually improving -- but more support is needed.

Study leader and ZSL researcher Ian Craigie said: "Although the results indicate that African national parks have generally failed to maintain their populations of large mammals, the situation outside the parks is almost undoubtedly worse. Many species like rhino are practically extinct outside national parks."

Director of ZSL Conservation Programmes, Jonathan Baillie, added: "The results are far worse than we imagined, but the increasing population trends in southern Africa provide hope and demonstrate that protected areas can be very effective for conserving large mammals if properly resourced.''

The study was undertaken by scientists from Cambridge University, the Zoological Society of London, RSPB and UNEP World Conservation Monitoring Centre with funding from the Natural Environment Research Council.