UNIVERSITY PARK, Pa. — Increased human activity around one of Africa’s most iconic ecosystems is “squeezing the wildlife in its core,” damaging habitat and disrupting the migration routes of wildebeest, zebra and gazelle, an international study has concluded. The findings are published this week in the journal Science.

The Serengeti-Mara ecosystem is one of the largest and most protected ecosystems on Earth, spanning 40,000 square kilometers and taking in the Serengeti National Park and Maasai Mara National Reserve in East Africa. Every year a million wildebeest, half a million gazelle, and 200,000 zebra make the perilous trek from the Serengeti park in Tanzania to the Maasai Mara reserve in Kenya in their search for water and grazing land.

Now, an international team of scientists has discovered that increased human activity along the boundaries is having a detrimental impact on plants, animals and soils.

“There is an urgent need to rethink how we manage the boundaries of protected areas to be able to conserve biodiversity,” said Michiel Veldhuis, lead author of the study from the University of Groningen in the Netherlands. “The future of the world’s most iconic protected area and their associated human population may depend on it.”

The study, led by the University of Groningen and with collaborators at 11 institutions around the world, including Penn State, looked at 40 years of data, and revealed that some boundary areas have seen a 400 percent increase in human population over the past decade, while larger wildlife species populations in key areas (the Kenyan side) were reduced by more than 75 percent.

The study reveals how population growth and an influx of livestock in the buffer zones of the parks has squeezed the area available for migration of wildebeest, zebra and gazelles, causing them to spend more time grazing less nutritious grasses than they did in the past. This has reduced the frequency of natural fires, changing the vegetation, and altering grazing opportunities for other wildlife in the core areas.

“We have long worried about the compression of protected areas due to agricultural conversion and how it affects both wildlife in protected areas and livestock in pastoral lands,” said Anna Estes, assistant research professor in the Huck Institutes of the Life Sciences at Penn State and an author of the paper. “It’s now clear that the intensification of agriculture and livestock-keeping around the borders is impacting ecosystem function even well within the protected area. This highlights the need to keep the rangelands outside protected areas productive and functioning, both for the pastoral livelihoods they support, and for the conservation of Tanzania’s flagship ecosystems and the services they provide.”

The impacts also are cascading down the food chain, favoring less palatable herbs and altering the beneficial interactions between plants and microorganisms that enable the ecosystem to capture and utilize essential nutrients.

The effects could potentially make the ecosystem less resilient to future shocks such as drought or further climate change, the scientists warn.

“We’ve been aware of the threats to migratory wildlife populations in smaller protected areas where they depend on access to increasingly human-dominated landscapes,” said Estes, “but the Serengeti-Mara ecosystem is one of our largest and best protected ecosystems, and even it is threatened by human impacts around its borders. This highlights the need to consider protected areas as integrated components in larger, shared landscapes, particularly in the face of a changing climate.”

The authors conclude that, even for reasonably well-protected areas like the Serengeti and Mara, alternative strategies may be needed that sustain the coexistence and livelihood of local people and wildlife in the landscapes surrounding protected areas. The current strategy of increasingly hard boundaries may be a major risk to both people and wildlife.

“We should re-think our protected area strategy, making sure that conservation efforts do not stop at protected area boundaries,” said Simon Mduma, director of the Tanzanian government’s Wildlife Research Institute and an author of the paper. “These results come at the right time, as the Tanzanian government is now taking important steps to address these protected areas boundary issues on a national level.”