Back to the Roots - Do Traditional Maasai Management Strategies Work towards Resilience against Unpredictable Rainfall and Grazing Pressure in Northern Tanzania?

Despite the importance for people´s livelihoods, many semi-arid African savannas are prone to heavy degradation due to overutilization by people, livestock and increased climate variability. Rangeland management, such as transhumance and deferred grazing systems, practiced by the Maasai in northern Tanzania, can be useful in combating the negative consequences of overuse and increasing rainfall variability. But little is known on how different rangeland regimes, practiced by the Maasai, impacts the productivity of these rangelands. We collected data on regrowth rates under different rangeland management regimes (rainy season grazing land, dry season grazing land, and seasonal exclosures), different harvest rates (month, season) and additional, uncontrolled grazing (fenced, open plots). We conducted the experiment for two consecutive growing seasons 2019 (GS1) and 2019/2020 (GS2). Grass regrowth rates were similar for all rangeland management regimes. During dry conditions in GS1 seasonally cut plots showed significantly higher grass regrowth compared to monthly cut plots, when fenced. Outside the fence grass regrowth was generally lower and similar for both harvest rates. During high rainfall conditions in GS2, seasonally cut plots showed higher grass regrowth independent of fencing. Regrowth rates of forbs were not impacted by any treatment during GS1. It increased by 5 times during GS2, and was significantly higher in the seasonally cut plots then. Our results suggest that recovery phases between heavy grazing events is crucial to maintain forage provision of the rangelands. Uncontrolled additional grazing can hamper the rangeland productivity during times of low rainfall, but seem not to have influence when rainfall is frequent. Traditional rangeland management is based on the concept of granting seasonal recovery periods, which seems to be an effective way to maintain rangeland productivity despite intense harvest and unpredictable rainfall pattern. Implementation and control of grazing plans are crucial, particularly during times of drought

Pre- and Post-Degradation Management of Rangelands: Implications for Sustainable Management

Rangeland degradation directly affects livestock production, resulting in food insecurity and ecological instability. A shift in vegetation from grass to woody plants has severely affected cattle production in Ethiopian rangelands. Those grass species that are perceived by the pastoralists as highly palatable and desirable are currently decreasing in both quality and quantity. A reason for this decline has been claimed to be degradation owing to overgrazing and climate change. While appropriate management of livestock density in rangelands is essential for sustainable production and grassland ecosystem health, the management of dryland ecosystems is mired in controversy due to the complexity of the ecosystem. This region is categorized as a non-equilibrium environment, though at times it experiences equilibrium characteristics, which makes the management of the Borana rangelands highly complex. A better understanding of grass productivity and its controlling factors in modern savanna ecosystems could be a key to understanding the productivity of savannas and to predict responses to future climatic changes. The development of effective management strategies for responding to climatic variability is often impeded by the lack of a systematic framework for analyzing livestock stocking policies and management practices. Further, effective decision making requires an understanding of the important biotic and abiotic components of rangeland systems, such as the response of rangeland vegetation to environmental stressors: climatic change and herbivorous population dynamics. Previous vegetation studies of the Borana rangelands focused mainly on taxonomic descriptions and rangeland condition assessments. Reseeding of degraded rangelands is a potential management option in eastern African rangelands to enhance the resilience of rangelands. Therefore, it is high time to understand how the native perennial grass individuals respond to increased herbivory under higher drought frequency after reseeding

Rangeland Management in a Changing World – Active and Passive Restoration Case Studies from Ethiopia, Tanzania, and South Africa

Rangelands cover almost 50% of the earth’s land surface and are often found in marginal areas that often face climate extremes. The production of herbaceous biomass has strongly declined over the last decades due to overgrazing and adverse climatic conditions such as frequent droughts and flooding. While different rangeland restoration methods are being used, their effect on vegetation quality and quantity over time has rarely been experimentally tested and monitored. Our research comprises experiments of various rangeland restoration tools we have used across eastern and southern Africa. We conducted passive restoration through exclosure experiments and compared vegetation in and outside of exclosures to understand regrowth patterns as well as overall forage quality. The active restoration methods we tested comprised domestic livestock species diversification, i.e., inclusion of browsers in rangeland systems. Further, we investigated how reseeding of nutritious rangeland grass species and subsequent grazing regimes can improve the rangeland health. We found that exclosures strongly improved biomass and productivity but that regular moderate grazing can further enhance those compared to no grazing. Our results further suggest that including browsers might enhance nutrients of herbaceous vegetation and soils of rangeland systems. We also claim that young grass species such as Chloris gayana and Cenchrus ciliaris, which are commonly used for reseeding of rangelands, show higher nutrient contents and productivity under light or moderate grazing pressure while mature grasses did not show this effect. We conclude that a combination of active and passive restoration methods can greatly enhance quality and quantity of African rangelands and enhance their sustainable use and resilience towards climatic shocks such as increasing drought frequencies

On the Move – Do Domestic and Wild Ungulate Species Distributions Overlap in the Mongolian Gobi?

In the Great Gobi B Strictly Protected Area (Great Gobi B), wild and domestic ungulates seasonally share the forage of the semi-desert and desert habitat. Around 130 herder families are grazing their livestock, mainly goats and sheep, in the protected area in winter. Wild ungulates of global significance in Great Gobi B include the reintroduced Przewalski’s horse (Equus ferus przewalskii),which had previously been extinct in the wild. To determine potential habitat overlaps between Przewalski’s horses and livestock, we mapped the movements of 19 livestock herds monitored via GPS collars and ranger observations of Przewalski’s horse herds over a one year period from September 2018 to August 2019. We additionally conducted focus group interviews with nomadic herders about their rangeland management. We found that pasture use in and around the Great Gobi B is still following the nomadic tradition, with herders moving camp locations on average eleven times per year, depending on forage availability. Our results show that the range of Przewalski’s horses and livestock mostly overlap around permanent and ephemeral water points. However, the same resources are used in different seasons. The protected area was recently expanded to twice its size, now also including additional herder households and traditional pastures. For the ongoing discussion about concerning the new zonation of the enlarged protected area it is important to consider both, herder and wildlife movements patterns, to meet the conservation goals of the protected area but also meet the needs of the traditional pastoral herding community

In search of the optimal management strategy for Arabian oryx

Extirpated from the wild in 1972 by overhunting, Arabian oryx (Oryx leucoryx) were re-introduced in Saudi Arabia in March 1990; 17 oryx were released into Mahazat as-Sayd, a 2244 km2 fenced reserve in westcentral Arabia, which lies at the periphery of their historical home range. The population has increased to 346 animals. The National Commission for Wildlife Conservation and Development, and those that manage the herd, have recently asked, ‘What is the optimal management strategy to assure long-term persistence of the species, given the absence of immigration and predation?’ Food resources, determinants of rates of mortality and birth, covary with unpredictable rainfall in Mahazat as-Sayd. Using data-driven assumptions, we developed a computer model that evaluated the probability of extinction (Pex) under various management strategies: no intervention, removing a fixed number of animals each year, removing a fixed percentage of animals each year, and removing all individuals above a threshold. In addition, we explored the probability that oryx populations would decline below two thresholds, called the probability of quasi-extinction (Pq-ex) under various management schemes. Our analyses suggested that, without intervention, the oryx population had a high Pex. Removing 15% of the current population provided a low Pex, but this method also produced high values for Pq-ex and, as a by-product, wide fluctuations in population size (N). Although it required an assessment of both N and carrying capacity (K), the most successful management plan consisted of removing all oryx above 70% of K. Adoption of this plan resulted in low Pex, low Pq-ex, and smaller fluctuations in N. Our study may provide a useful model for evaluating management plans for a variety of threatened animal populations in desert ecosystems.Funding for this project was received from the National Wildlife Research Center, Taif, Saudi Arabia, and from the Columbus Zoo, Columbus, OH

Moving towards the greener side: environmental aspects guiding pastoral mobility and impacting vegetation in the Dzungarian Gobi, Mongolia

Livestock grazing often intensifies around herder camps, which can lead to degradation, particularly in arid areas, where vegetation is scarce. In Mongolia, nomadic herders have covered long distances between camps and changed camps regularly for centuries. However, changing socioeconomics, rising livestock numbers, and climatic change have led to growing concerns over rangeland health. To understand travel mobility and livestock grazing patterns, we combined Global Positioning System tracking data of goats, remotely sensing pasture productivity, and ground-based vegetation characteristics in the Great Gobi B Strictly Protected Area, Mongolia. We assessed herder preferences for camp selection, followed 19 livestock herds over 20 months, determined use and nutrient contents of the most dominant plant communities, and estimated plant species richness, vegetation cover, and biomass within different grazing radii around camps. Biomass availability was key for herder decisions to move camps, but in winter, other factors like shelter from wind were more important. Camps were mainly located in Stipa spp. communities, agreeing with herder preferences for this highly nutritious species, and its dominance around camps. Herders changed their camp locations on average 9 times yearly, with a maximum distance of 70–123 km between summer and winter camps, and an average visitation period of 25–49 d per camp, depending on season. Small livestock spent > 13−17 h daily within a radius of 100 m from camp, and livestock use intensity decreased steeply with distance from camp but was remarkably similar around spring, autumn, and winter camps on the Gobi plains. However, we found little evidence for a corresponding gradient in plant species richness, biomass, and cover on the Gobi plains. The high mobility of local herders and the overriding impact of precipitation on pasture dynamics contribute to a sustainable vegetation offtake by livestock in the nonequilibrium rangelands of the Dzungarian Gobi.publishedVersio

Bionomics of the African Apefly (Spalgis lemolea) as A Potential Natural Enemy of the Papaya Mealybug (Paracoccus marginatus) in Tanzania

This research article published by MDPI, 2020The African apefly (Spalgis lemolea Druce) is a potential natural enemy of the papaya mealybug (Paracoccus marginatus Williams and Granara de Willink). We studied the life history of apeflies in the laboratory at a temperature of 25–27 °C and a relative humidity of 55%–65% under a 12 h photoperiod condition. The papaya mealybugs and apefly larvae were collected from papaya plants in Tengeru, Arusha, Tanzania. The papaya mealybugs were introduced and allowed to multiply on potted sprouting potato plants in screened cages. In order to study the life cycle and predation of apeflies, an apefly egg was placed on an open screen-covered petri dish containing a moist blotter paper and observed for larva emergence. After the apefly larva emergence, a mixture of mealybug eggs (up to 1500), nymphs (200–250) and adults (100–150) was introduced in the petri dish each day and the consumption rate by the apefly larvae was quantified until the larvae reached pupal stage. Then, the apefly adults were collected and put into cages 30 cm × 30 cm × 30 cm containing cotton wool soaked in water, for observation of pre-mating, mating, egg-laying and life span. Results indicate that the apefly completed its life cycle in 23 days. The mean development period of the eggs was four days and the development period for the larva, pre-pupa, and pupa was nine, one and ten days respectively. The adult apefly emerged after 9 days of the pupa stage with mean body lengths of 10.1 ± 0.4 mm and 11.0 ± 0.8 mm for the males and females, respectively. The female laid an average of 68 eggs in groups of two to seven at different sites after 4–5 days of emergence. In this study one apefly larva was capable of consuming about 1983 ± 117, 123 ± 6 and 80 ± 9 papaya mealybug eggs, nymphs and adults respectively during larval stage. These results reveal the predatory potential of the apefly in suppressing the population of papaya mealybugs under field conditions

Can diverse herbivore communities increase landscape heterogeneity? Comparing wild and domestic herbivore assemblages in a South African savanna

This research article published by Elsevier, 2015The structure and composition of woody and grassy vegetation in savannas is strongly influenced by herbivores. In recent decades, the proportion of browsers has declined across African savannas in favour of more grazers, triggered by large-scale human-induced cattle grazing. This has led to overgrazing and an imbalance of woody and grassy vegetation. Our study investigated mono-specific and multi-species herbivore assemblages of varying density and assessed similarities in vegetation patterns under wildlife and livestock herbivory in and around Kruger National Park, South Africa. Under mono-specific herbivory, overall tree cover was more than twice as high compared to multi-species herbivory while the branching height of small and tall trees was lowest. Small tree and bush densities were strongly elevated at mono-specific compared to multi-species herbivore sites. Tall trees were dominated by Acacia nigrescens under multi-species herbivory at low wildlife density but not at high density sites. Grass leaf nitrogen contents were almost twice as high at multi compared to mono herbivory sites, particularly beneath tree canopies. Livestock and wildlife herbivore sites showed similar patterns in their woody plant structure and grass nutrients. We conclude that a characteristic herbaceous and woody vegetation structure as well as species composition can be matched with mammalian herbivore communities, which has implications for landscape heterogeneity and grazing management in savanna systems

Spatio-temporal invasion dynamics of Maesopsis eminii in Amani Nature Forest Reserve, Tanzania

This research article published by Elsevier B.V., 2020Globally, invasive plant species cause negative impacts to human livelihoods and natural ecosystems, particularly in biodiversity hotspots. Maesopsis eminii invasion in Amani Nature Forest Reserve, Tanzania, was considered an ecological disaster in the 1980s. After >50 years have elapsed since the species was first introduced in the reserve, there is yet little information available on its invasion progress. We assessed spatio-temporal invasion dynamics using forest inventory data collected in 1998 and resurveyed 60 (20 m × 50 m) sample plots in 2018. Among resurveyed plots, 30 had been invaded by M. eminii in 1998 and other 30 sample plots as control, which had no M. eminii in the year 1998. We also assessed vegetation cover change over a 20 year period between 1998 and 2018 using Landsat satellite images. Over the last 20 years, 23% of control plots were newly invaded by M. eminii. Tree species richness was 25% lower in invaded versus control plots (U = 1490, z = 2.9, p = 0.04). Large trees (DBH ≥ 31–50 cm) of Maesopsis eminii were most abundant (62%) in invaded plots whereas small trees (DBH ≤ 10 cm) were most abundant (>50%) in control plots, indicating that the tree species might be prone to self-thinning. Woody species diversity was significantly lower in invaded (1.63 ± 0.49) vs control plots (1.87 ± 0.35; t(58) = −2.19, p = 0.03). The number of M. eminii individuals ha−1 was positively associated with higher altitudes ranging above 800 masl (ρ = 0.33, P = 0.011) but there was no correlation with distance away from the forest reserve boundary (ρ = 0.11, P = 0.394;) nor with distance away from village centers (ρ = −0.08, P = 0.502). Change detection analysis indicated about 1,108 ha of non-forest vegetation had regrown into forest over the last 20 years, particularly in the south - western region of the reserve. The region included 4 sample plots newly invaded by M. eminii. We conclude that there is an increase in spatial distribution of M. eminii individuals between the year 1998 and 2018. Furthermore, M. eminii has low regeneration potential in already invaded sites of high invasive density and only slowly invading gaps in uninvaded sites

Anthropogenic Pressure on Tree Species Diversity, Composition, and Growth of Balanites aegyptiaca in Dinder Biosphere Reserve, Sudan

This research article published by MDPI, 2021Anthropogenic disturbances, such as illegal harvesting and livestock browsing, often affect natural forests. However, the resulting tree species diversity, composition, and population structure have rarely been quantified. We assessed tree species diversity and importance value indices and, in particular, Balanites aegyptiaca (L.) Del. population structure, across 100 sample plots of 25 m × 40 m in disturbed and non-disturbed sites at the Dinder Biosphere Reserve, Sudan, from April 2019 to April 2020. We found that the tree species diversity in non-disturbed sites was more than double that of disturbed sites (p < 0.001, T = 32.6), and seedlings and saplings comprised more than 72% of the entire tree population (F2,48 = 116.4, p = 0.034; F2,48 = 163.2, p = 0.021, respectively). The tree density of B. aegyptiaca in the disturbed site was less than half that of the non-disturbed site (p = 0.018, T = 2.6). Balanites aegyptiaca was seven times more aggregated in disturbed sites compared to more regularly spaced trees in non-disturbed sites (T = 39.3 and p < 0.001). The poor B. aegyptiaca population status of the disturbed site shows that the conservation of this vulnerable species is essential for a sustainable management and utilization scheme