Understanding how predation risk and plant defenses interactively shape plant distributions is a core challenge in ecology. By combining global positioning system telemetry of an abundant antelope (impala) and its main predators (leopards and wild dogs) with a series of manipulative field experiments, we showed that herbivores' risk-avoidance behavior and plants' antiherbivore defenses interact to determine tree distributions in an African savanna. Well-defended thorny Acacia trees (A. etbaica) were abundant in low-risk areas where impala aggregated but rare in high-risk areas that impala avoided. In contrast, poorly defended trees (A. brevispica) were more abundant in high- than in low-risk areas. Our results suggest that plants can persist in landscapes characterized by intense herbivory, either by defending themselves or by thriving in risky areas where carnivores hunt.

1. Citizen science is gaining increasing prominence as a tool for science and engagement. However, despite being a potentially valuable tool for sustainable development, citizen science has little visibility in many developing countries.2. We undertook a collaborative prioritisation process with experts in conservation and the environment to assess the potential of environmental citizen science in East Africa, including its opportunities, benefits and barriers. This provided principles that are applicable across developing countries, particularly for large-scale citizen science.3. We found that there was great potential for citizen science to add to our scientific knowledge of natural resources and biodiversity trends. Many of the important benefits of citizen science were for people, as well as the environment directly.Major barriers to citizen science were mostly social and institutional, although projects should also consider access to suitable technology and language barriers. 4. Policy implications. Citizen science can provide data to support decision-making and reporting against international targets. Participation can also provide societal benefits, informing and empowering people, thus supporting the United Nations'This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

African savannas support an iconic fauna, but they are undergoing large-scale population declines and extinctions of large (>5 kg) mammals. Long-term, controlled, replicated experiments that explore the consequences of this defaunation (and its replacement with livestock) are rare. The Mpala Research Centre in Laikipia County, Kenya, hosts three such experiments, spanning two adjacent ecosystems and environmental gradients within them: the Kenya Long-Term Exclosure Experiment (KLEE; since 1995), the Glade Legacies and Defaunation Experiment (GLADE; since 1999), and the Ungulate Herbivory Under Rainfall Uncertainty experiment (UHURU; since 2008). Common themes unifying these experiments are (1) evidence of profound effects of large mammalian herbivores on herbaceous and woody plant communities; (2) competition and compensation across herbivore guilds, including rodents; and (3) trophic cascades and other indirect effects. We synthesize findings from the past two decades to highlight generalities and idiosyncrasies among these experiments, and highlight six lessons that we believe are pertinent for conservation. The removal of large mammalian herbivores has dramatic effects on the ecology of these ecosystems; their ability to rebound from these changes (after possible refaunation) remains unexplored.

Assessing the direct and indirect consequences of nonrandom species removal within guilds of strongly interacting species, such as large mammalian herbivores, is an important goal in basic and applied ecology. The ecological impacts of such perturbations are often contingent on abiotic conditions, which have hindered efforts to generalize the results of field experiments. Thus, there is a need for experiments that selectively remove different species from ecologically important guilds and that are replicated across environmental gradients. In 2008, we constructed a series of size‐selective large‐herbivore exclosures across a natural rainfall gradient in semi‐arid Kenyan savanna. This experiment (“UHURU”, for ungulate herbivory under rainfall uncertainty) aims to (a) characterize the effects of successively removing the largest size classes of herbivores from the system and (b) evaluate how the direction and magnitude of these effects are shaped by variation in precipitation regimes. UHURU consists of three electrically fenced herbivore‐exclusion treatments and an unfenced control, applied to blocks of contiguous 1‐ha plots. The three fenced treatments are: “Mega” (exclusion of elephants and giraffes only); “Meso” (exclusion of both megaherbivores and mesoherbivores, ∼40 kg and larger); and “Total” (exclusion of all herbivores ≥5 kg). Each block of treatments is replicated three times at each of three sites along the 20‐km rainfall gradient (increasing from 439 mm/yr in the north to 639 mm/yr in the south, with little background variation in soil attributes and species composition). We present data, spanning 2008–2013, from (a) biannual surveys of understory plants at 49 staked grid points within each of the 36 1‐ha plots (1764 total stakes); (b) annual woody‐plant censuses within the central 0.36 ha of each plot; (c) annual and semi‐annual monitoring of individually marked woody plants; (d) small‐mammal capture–mark–recapture sessions conducted every other month in total‐exclusion and open plots; (e) daily rainfall monitoring throughout the course of the experiment; and (f) quarterly large‐mammal dung surveys.

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