This study focuses on community-based knowledge to analyze the impacts of range enclosures, crop farming, fire suppression and bush encroachment on the communal rangelands of Borana, southern Ethiopia. The knowledge of local herders is the basis for decision making in the utilization and management of grazing lands. We used Borana oral history associated with the period of the gada system to reconstruct environmental change that spans a period of 48 years. Our results show that the use of communities' perceptions as a basis for evaluating the impacts of land use change on the environment makes an important methodological contribution. Communities' responses to changing land use resulted in the development of range enclosures, the expansion of crop farming and the fragmentation of the communal rangelands, while the suppression of fire contributed to the expansion of bush encroachment. The overall impact was forage scarcity and greater vulnerability of stock during drought years. We conclude that policymakers could use communities' knowledge of environmental change to improve the use of the rangelands. We propose that sustainable use of the southern rangelands in the future will require a greater focus on regulating the expansion of enclosures, crop farming and ranching, as well as reintroducing fire where necessary, to control the expansion of bush cover.

Summary 1.The relationship between biomass and species richness in temperate vegetation has been described as a hump-back response model. The hump-back model predicts that herbaceous species richness is highest at an intermediate level of biomass. However, this has not been investigated in arid-zone grazing lands. 2. We tested the hump-back prediction in an arid tropical grazing region in northern Kenya where a seasonal grazing exclosure system is practised. We compared vegetation structure, species richness and composition on an open range and exclosures at five sites to elucidate the potential mechanisms behind variation in species richness. 3. More biomass was accumulated within seasonal exclosures than in continuously grazed areas. Species richness in exclosure plots varied from 5·3 to 8·3 species m -2 , while that in open plots varied from 5·1 to 7·5 species m -2 . A pair-wise test showed no difference in two of the five sites with respect to both total and herbaceous species richness. 4. The primary floristic gradient illuminated through ordination was related to biomass, while the secondary gradient was related to species richness. The exclosure plots had more abundant species, especially compared with open plots, which had more rare and occasional species. A total of 37 herbaceous species was recorded; 22% were indifferent to grazing, 30% grazing intolerant and 48% promoted by grazing. 5. The relationship between biomass and herbaceous species richness showed (i) no trend within the exclosures (maximum biomass 800 g m -2); (ii) a positive trend in the open grazing land (maximum of 500 g m -2 ); and a hump-back pattern when (i) and (ii) were analysed together. Optimum richness corresponded to a biomass level of 400 -500 g m -2 . Species richness declined with increase in age of exclosures. 6. We confirmed that species richness will decline when biomass exceeds 500 g m -2, as predicted by the hump-back model, even in arid grazing lands. Seasonal grazing exclosures may increase species richness to a certain level, but the decline in species richness with age of exclosures indicates that long-term exclusion of grazing may not necessarily increase species richness in arid-zone grazing lands.

This paper compares land degradation assessment techniques using indigenous ecological knowledge (IEK) of the Booran pastoralists and techniques used by ecologists. The study was conducted at landscape and regional levels in southern Ethiopia, where the Booran pastoral production system comprised the // / Golbo (lowlands), the // Dirre (Plateau) and the // / Liiban production systems (hereafter also referred to as regions). The study, by involving traditional range scouts in evaluating landscape and regional level environmental changes, challenges the notion that IEK is mythical and could not meet scienti®c rigour. We show that the use of common soil and vegetation indices allows comparisons of land degradation assessments between the IEK of the pastoralists and ecological techniques. Evaluation by traditional range scouts (TRSCs) and range ecologists (REs) on changes in range conditions and trends showed high correlations. Indigenous ecological knowledge was effectively used to determine landscape suitability and potential grazing capacity of individual landscapes and at regional levels. We show different perceptions in interpreting grazing suitability and potential grazing capacity. Management did not change the latter, which is an inherent property of individual landscapes, while the former could be altered. Both TRSCs and REs made comparable predictions on threats to range conditions and trends, but interpreted landscape stability differently. We suggest that integrating IEK in the ecological methods would help identify important perceptions of the pastoralists on effects of land use on local landscapes. Moreover, the value of IEK should also be considered when monitoring landscape level changes as well as when assessing degradation of the grazing lands. We hope the information in this paper will motivate policy-makers to incorporate the IEK of the pastoralists into decisions on landscape level range rehabilitation.

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Sacred groves, some as old as several centuries, may have contributed to the preservation of some plant species in Tanzania. This has led conservationists to consider whether sacred groves could be used for in situ conservation. Eight sacred groves of the Ugunda chieftaincy of the Wanyamwezi in central Tanzania representing burial sites that varied from 6-300 years old were inventoried to compare woody species richness and taxonomic diversity with those of forest plots in a state managed Forest Reserve. Although they occupied a relatively small area the sacred groves had greater woody species richness and taxonomic diversity than the state managed Forest Reserve. The forest plots and the groves shared a species similarity index of 45%, suggesting that the sacred groves contributed to in situ conservation of the miombo woodland biodiversity. Some of the woody species were absent in the forest plots, also suggesting that groves served as a refuge for some species. An inventory of all existing sacred groves could provide important information on their role in in situ conservation. In order to promote them for community-based conservation of biodiversity the government should declare sacred groves as preservation sites, and incorporate them into modern conservation systems.