Getting better with age: Lessons from the Kenya Long-term Exclosure Experiment (KLEE)

Abstract

The Kenya long-term exclosure experiment (KLEE) was established in 1995 in semi-arid savanna rangeland to examine the separate and combined effects of livestock, wildlife and megaherbivores on their shared environment. The long-term nature of this experiment has allowed us to measure these effects and address questions of stability and resilience in the context of multiple drought-rainy cycles. Here we outline lessons learned over the last 29 years, and how these inform a fundamental tension in long-term studies: how to balance the need for question-driven research with the intangible conviction that long-term data will yield valuable findings. We highlight the value of (1) identifying experimental effects that take many years to manifest, (2) quantifying the effects of different years (including droughts) and (3) capturing the signatures of anthropogenic change. We also highlight the potential for long-term studies to create a collaborative community of scientists that brings new questions and motivates continued long-term study.

Keywords: delayed responses; drought; environmental change; herbivore exclosures; livestock; mega‐herbivores; year effects.

FIGURE 1

(a) Schematic of the Kenya Long‐term Exclosure Experiment (KLEE), showing the layout of the different herbivore treatment plots (using semi‐permeable barriers) and the multiple embedded experiments. The letters inside each plot represent the (combinations of) large mammalian herbivores allowed access: C, cattle; W, meso‐herbivores (25–800 kg); M, megaherbivores (>1000 kg); O, no large herbivores allowed. ‘Glades’ are treeless anthropogenic patches arising from long‐abandoned cattle enclosures (‘bomas’). Photos illustrate (A) cattle grazing in a C plot, with entry gate in lower right, (B) cattle and plains zebras in a recently burned WC plot, (C) KLEE crew conducting a controlled burn in one of the plots. (b) Some of the many relationships demonstrated and inferred from KLEE. Variables in red and orange boxes have been experimentally manipulated (as well as being measured as response variables). Red boxes are experimental manipulations fully embedded in and crossed with the KLEE herbivore treatments; orange boxes are separate replicated experimental manipulations associated with KLEE. Arrows indicate the direction of each demonstrated effect. Not all relationships have been represented here. For example, termite mounds strongly modify plant communities and provide refuges and stable burrows for both snakes and rodents. Interactive effects are not illustrated, like the fact the elephants mitigate the effects of cattle on other ecosystem variables (Young et al., 2022). Also not included here are the rich set of experimental and descriptive studies of anthropogenic glades associated with KLEE (Porensky & Veblen, , ; Veblen, ; Veblen & Porensky, ; Veblen & Young, 2012). This figure was updated and adapted from Young et al., .

FIGURE 2

Timeline of the Kenya Long‐term Exclosure Experiment (KLEE), highlighting some key developments and funding (the latter does not include multiple NSF GRF, DDIG, REU and ROU grants). Herbivore treatments include separate and combined exclusions of meso‐herbivores, mega‐herbivores, cattle and rodents. Dung counts are carried out to estimate herbivore use of different treatments. Drought events are highlighted in orange. Brown dots are soil surveys. An adjacent rainfall manipulation experiment was initiated in 2017. The numbers in blue beneath each date are the cumulative numbers of peer‐reviewed publications from the project. These totals do not include 33 outreach publications or 30 American and Kenyan graduate dissertations.