Wildebeest and zebras and some other ungulates migrate to better pastures in order to survive. They graze in areas in the south and then move on to the north, and end up in Masai Mara, where they give birth. Some time later, they return. Maasai don't migrate with their cattle to Masai Mara because there is a disease that cattle can get from the placentas of wildebeest who have given birth.

In it's annual migration from Ngorongoro, through the Serengeti, across the Mara River and into Kenya to the Masai Mara, the wildebeest is an important animal in several ways:

• Tourism - large numbers of tourists follow migrations every year.

• Benefit to the environment

In February, the migration passes through the south part of  Serengeti National Park and in the Ngorongoro Conservation Area. This period is the peak season for fertility for antelopes and important for the formation of the next generation. New antelopes are born during this season, and visitors may see the young walking with the herd.

Spanning across northern Tanzania is 30,000 square kilometers (12,000 sq mi) of rich grasslands. The name Serengeti is said to come from the Maasai people meaning "endless plains." Among the gazelles, zebras, and antelopes that call this place home, there is one grazer that rules them all, the blue wildebeest. As a keystone species, blue wildebeests are essential in keeping this African prairie a carbon sink.

https://www.oneearth.org/species-of-the-week-blue-wildebeest/

In the mid-20th century, the blue wildebeest population was decimated to just 300,000 individuals because of disease. Ground vegetation began to overpopulate which eventually led to wildfires that destroyed 80% of the ecosystem annually. This led to a net release of carbon dioxide into the atmosphere, making the Serengeti a producer of greenhouse gases. When disease management efforts helped the wildebeest population recover back to their historic levels of over 1.5 million, the landscape was brought back into balance and restored to being a natural storage unit for CO2 in less than a decade. 

Today, the blue wildebeest population is stable and considered of least concern by The International Union for Conservation of Nature (IUCN).  The rewilding of wildebeests in the Serengeti is considered one of the most successful rewilding stories of our time. Rewilding efforts can not only save species and restore habitats -  it is also an essential solution in the fight against the climate crisis.

The wildebeest population was 1.2 million in 1975 and 1.5 million as of 2020.

Without the Indigneous Maasai people, their land, which is a passage way for the great migration of widebeest and other grazing animals, would become a place for hunters with huge elaborate hunting lodges, many in the path of the wildlife corridors.

The Maasai people in the Ngorongoro Conservation Area are under the threat of eviction from their homeland.

Termite Mound blog

The War Against the Maasai of Loliondo and NCAA Continues

It is not a nightmare that you can wake up from. The horror is real. The threat, lobbied for by OBC, that organize hunting for Sheikh Mohammed of Dubai, of taking 1,500 km2 of grazing land from the Maasai of Loliondo - squeezing them into land with towns, agricultural areas, forest reserves, and a nasty American land grab – was last year implemented with brutality and lawlessness by the Tanzanian government. The ugly boundary beacons still stand there and the Maasai can only access their own land as thieves, risking terrible extortion by rangers, which is a risk that must be taken, since cows need grass.