The annual migration of 1.3 million wildebeest through Tanzania’s Serengeti and Kenya’s Masai Mara is a spectacle that draws hundreds of thousands of tourists and has earned a spot on Unesco’s list of World Heritage sites. This emblematic migration also plays a crucial role in maintaining the ecological balance of ecosystems.

Regrettably, such grand annual migrations are now limited to a handful of locations across Africa.

Roads, fences, farms and urban sprawl have fractured the historic migratory routes of wildebeest herds and prevented them from roaming far and wide in search of fresh grass and water. A recent study by researchers from the University of Copenhagen and published in Nature Communications Journal, says this has impacted negatively on the genetic wellbeing of wildebeest populations.

“Our results clearly show that wildebeest populations which no longer migrate, but have historically done so, are simply less genetically healthy than those that continue to migrate. And this weakens their chances of long-term survival,” says Rasmus Heller, one of the study’s lead authors.

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Scientists examined the complete genetic makeup of 121 wildebeest spanning their entire range, from South Africa to Kenya, delving into the genetic repercussions of migration in wildebeest.

“Wildebeest are dependent on migrations to support their large numbers. They can survive in resident, non-migratory populations, but their numbers simply shrink when they cannot migrate. We see this in parts of Kenya and Tanzania that have prevented them migrating and showing numbers decreased as a result,” says co-author Joseph Ogutu, senior statistician at the University of Hohenheim.

“Migrations make wildebeest a keystone species in ecosystems. Their grazing keeps vegetation healthy, transports and distributes nutrients, while they themselves serve as prey for predators and carrion for scavengers. It isn’t just the iconic animal we threaten when we prevent them migrating – but many other species as well, as it does the enormous tourism revenue that benefits governments and local communities.”

Over centuries, the populations of two wildebeest subspecies, the Western white-bearded wildebeest and the Eastern white-bearded wildebeest, have dwindled. Historically, both subspecies undertook extensive migrations, with large populations.

While the Western subspecies found protection in the Serengeti-Mara from the 1950s, human activities since the early 1900s have threatened the Eastern subspecies. Presently, only 6,000-8,000 Eastern, white-bearded wildebeest remain, divided into small, isolated groups.

In Botswana in particular, fencing to protect cattle from coming into contact with migratory wild animals was put up in recent times. Botswana’s Kalahari population declined from roughly 260,000 in the 1970’s to fewer than 15,000 in the late 1980s.