Water, Savannas, and Society

2007-Present Program Initiative

The productivity of savannas in semi-arid regions of the world and their ability to support wildlife and herds of pastoral livestock ultimately depend on water. Unfortunately, rainfall is unpredictable, and becoming more so in the face of climate change. Such uncertainty often leads to increases in livestock herd sizes by the pastoralists of the Ewaso ecosystem of Kenya as they try to cope with the resulting income fluctuations. A ‘tragedy of the commons’ often develops which, in turn, leads to habitat degradation.

This research and teaching project integrates the talents of hydrologists, ecologists, and political scientists to determine the linkages and feedbacks that connect water to vegetation production, wildlife and animal movements, and the economic and health of the pastoral peoples that share the landscape with wildlife.

We have shown that the intensity of rainfall events has increased, decreasing the amount of rain penetrating the soil and increasing runoff, removing water from the ecosystem. At the same time, as grazing has increased, native grasses have declined while inedible vegetation has increased.

Pastoral herders appear to adjust the behaviors of their herds in a way that sustains grasslands, and the majority believe that herding intensity is not too great. Under normal rainfall conditions our findings suggest that their assessment of herding pressure is likely to be true. But where environmental uncertainty is the norm and droughts are frequent, greater changes in behaviour will be required.  Our findings are identifying ways of transforming the water cycle to hopefully help the Laikipia pastoralists of central Kenya adopt more sustainable rangeland practices under a wider range of environmental conditions.

Educational Impacts

A course entitled “Water, Savannas, and Society” was developed at the start of the project for graduate students to explore how issues of water availability and use at different scales affected both the functioning of ecosystems and the development of sustainable human societies. It has also been converted into an upper-level undergraduate course centered around ‘resilience thinking,’ which has increased the number of students participating in EEB’s Kenya field semesterand continuing to work on problems posed in the course for senior thesis.

Future Directions:

As anticipated results emerge on the ways in which wildlife and livestock grazing feeds back on vegetation dynamics and water retention as well as how herding decisions impact health and economic gains both within and between pastoral communities, models capturing these complex relationships will be developed that can be used to work with pastoral herders to explore ‘what if’ alternative herding strategies and identify which rangeland outcomes are desirable and obtainable. In addition, emerging knowledge about livestock-rangeland dynamics is leading to the development of alternative herding practices and the testing of assumptions about their efficacy.

Participating Department

Collaborating Institutions

Related Media and Press Coverage


Professor, Ecology & Evolutionary Biology


Research Associates

  • Sandro Azaele Hewlett
  • Elizabeth King
  • Mahiri Mwita
  • R. Muneepeerakul
  • Corinna Riginos
  • Wilfred Odadi

Graduate Students

  • Hassan Boru, Nairobi University
  • Ryan Chisholm
  • Trenton Franz
  • Stephanie Hauk
  • Corinne Kendall
  • Joseph Kirathe, Nairobi University
  • Eva Kaye-Zwiebel
  • Alex Lester
  • Luke MacDonald
  • Blair Roberts

Undergraduate Students