^{(Photograph = elephants in area colonized by Opuntia, Shirley Strum)}

Introduction

For over 40 years Dr. Shirley Strum has been studying baboons in Kenya. During that time she also observed the people, other animals, plants, and climate. Also during that time, one of her arid research areas was invaded and colonized by Opuntia–an alien species.

The Details

Laikipia, in Kenya, was once virtually uninhabited, it’s now being steadily degraded by the incursion of land-hungry Homo sapiens and also by the spread of Opuntia stricta, otherwise known as the prickly pear (Sydney Morning Herald).

Opuntia was present in the general area for at least 50 years before it became an invasive weed, and its spread corresponded to increasing degradation of the grassland. However, there are many questions. Despite what we know, there are many facets to the story of Opuntia in Dr. Strum’s study area. How did it arrive in the general area; was it a garden plant first? Why did it spread? What are the precise roles of humans or animals in its spread? Is the invasion caused by climate change? Will it continue to invade new areas?

Opuntia stricta and O. dillenii are some of the most invasive plants in the world in arid areas. Native animals spread their seeds. Cladodes are carried to new areas by large fauna or occasional cloudbursts accompanied by flash floods. The plants themselves adeptly exploit wet periods followed by long drought. Humans often provide perfect lands to colonize when urban encroachment or agriculture denude once tightly balanced ecosystems. Moreover, Opuntia species grow well on poor soils.

Baboons spread Opuntia in Kenya as do elephants and goats; likely birds and other fauna are responsible for dispersing the plants too. Probably the invaded lands are forever altered by the factors that help the Opuntia invasion. The results of ecosystem change are yet to be fully understood.

If you want to help Dr. Strum’s conservation efforts, visit BaboonsRUS.

Additional Reading: Invasion of Opuntia in Kenya