Rangeland dynamics in southern Ethiopia: (3). Assessment of rangeland condition in relation to land-use and distance from water in semi-arid Borana rangelands

The condition of the semi-arid Borana rangeland in southern Ethiopia was assessed by studying different land-use systems (communal land, a government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. The assessment incorporated the soil, herbaceous and woody plant layers. Two methods were employed to evaluate the grass layer, viz. ecological condition index (ECI) and weighted palatability composition (WPC). The ECI on the government ranch was 21.7% and 26% greater than that of the traditional reserve and the communal land, respectively. The WPC on the government ranch was 83.3% and 48.6% greater than that of the communal area and the traditional reserve, respectively. Both ECI and WPC values were similar for all distance sites from water. Tree equivalent (TE) density, of all encroaching woody plants combined, was higher on the communal land (504 TE ha(-1)) than the government ranch (373 TE ha(-)1) and traditional grazing reserve (118 TE ha(-1)), but with no marked variations in the distance sites from water. Height class distribution of encroaching woody plants in the study areas showed the largest abundance (range: >50-100%) at the height class >0-2m. Tree equivalents per hectare of encroaching woody plants were negatively correlated (r = -0.60) with ECI and WPC and positively correlated (r=0.87) with percentage bare ground. The correlation (r = 0.50) between percentage bare ground and soil compaction was positive and low. Although the government ranch had a greater composition of highly palatable grass species than the other land uses, the rangeland was not in good condition due to severe bush encroachment. The communal land was generally in poor condition. In the traditional grazing reserve, bush encroachment was not a problem, but the productivity of the grass layer was poor when assessed on the basis of ecological and palatability merits. The negative interaction of TE density of all encroaching woody plants combined with ECI or WPC and the positive interaction with bare ground, may suggest that the abundance of these species is more critical in aggravating deterioration in grassland productivity. Therefore, the priority of any bush control program must be towards minimizing the abundance of these woody plants.     

Rangeland dynamics in southern Ethiopia: (1) botanical composition of grasses and soil characteristics in relation to land-use and distance from water in semi-arid Borana rangelands

The distribution and compositional pattern of the grass layer, as well as soil quality of southern Ethiopian semi-arid rangelands were examined under three land-use systems (communal land, government ranch and a traditional grazing reserve enclosure) and along a distance gradient (near, middle and far) from water sources. In total, 49 grass species were identified, 65% of which were perennials. Of the most commonly distributed highly desirable species, Chrysopogon aucheri showed the greatest frequency under the traditional grazing reserve (27.6%), and the lowest in the communal land (14.0%). The frequency of Cenchrus ciliaris was similar in all the study sites. The proportion of Lepthotrium senegalensis was low under the land-use systems (3.9%) and increased away from water sources (2.3%). Of the less desirable species, Sporobulus nervosus was extremely more abundant (<0.05) in the communal land (13.3%) than the traditional grazing reserve (3.3%) and the government ranch (1.9%). Sporobolus pyramidalis was dominant in the study sites, with similar (P>0.05) frequency percentages under the land-use systems and along the distance gradients from water. Basal cover was low and similar on all the study sites (3.3%). Concerning the soil texture, sand (71.1%) constituted the largest proportion, followed by silt (21.3%) and lastly, clay (7.7%). With regard to soil exchangeable cations, organic C and total nitrogen were generally low and did not show marked variation in all the study sites. The study showed significant differences for most of the vegetation variables between the communal land and the other land-uses. This suggested that grazing intensity was higher in the communal land and moderate in the government ranch and in the traditional grazing reserves (kallos). The lack of significant differences in most of the studied (vegetation) variables along the distance gradient from water could be ascribed to the fact that grazing disturbance has already exceeded a certain threshold of degradation. Under the present low states of soil nutrients and rainfall, cultivation is neither sustainable nor environmentally friendly and this will lead to further degradation of the soil in these marginal lands.     

Cattle-rangeland management practices and perceptions of pastoralists towards rangeland degradation in the Borana zone of southern Ethiopia

A survey was conducted in the Borana pastoral areas of southern Ethiopia to assess current livestock production systems, rangeland management practices and the perceptions of the pastoralists towards rangeland degradation. This information is considered vital to future pastoral development planning and interventions. Data were collected from a total of 20 villages that were identified from 5 peasant associations, namely Did Yabello, Moyatte, Did Harra, Dubuluk and Melbana. The average household size in the study area was 7.23. The majority of the pastoralists relied on both livestock and crop farming. The average livestock holding per household was 14 cattle, 10 goats, 6 sheep and 2 camels. Livestock holdings, with the exception of camels, has shown a declining trend over time. The two most important traditional rangeland management strategies adopted by the pastoralists included burning and mobility, but since 1974/75 burning has no longer been practised. With regard to mobility, the livestock herding falls in two categories, namely: home based and satellite herding. The former involves the herding of milking cows, calves and immature animals (<2 years) close to the encampments. The latter constitutes the herding of bulls and immatures (>2 years) further away from the encampments. Based on the pastoralists' perceptions, the major constraints on livestock production in descending order, were recurrent drought, feed and water scarcity, animal diseases, predators and communal land ownership. All the respondents considered the condition of the rangelands to have declined dramatically over time. In the past most development policies were based on equilibrium theories that opposed the communal use of the rangelands and traditional range management practices. The way in which the pastoral system affects the rangeland ecosystem functioning is contentious to this theory and the 'tragedy of the commons'. There was also a perceived problem of bush encroachment and the ban on traditional burning practices and recurrent droughts were seen as aggravating factors to this invasion process. The increasing practice of crop cultivation on the rangelands was identified as a serious threat to future livestock production and traditional resource management practices. Suggestions for possible interventions to improve the productivity and sustainable use of these rangelands are made.     

Understanding large-scale deforestation in southern Jinotega, Nicaragua from 1978 to 1999 through the examination of changes in land use and land cover

Nicaragua, home to the largest remaining extent of rainforest in Central America (total surface area) and to a significant indigenous population, has lost approximately half of its forest cover since 1950. This major and rapid loss of forest cover has been explained as the consequence of an eastward moving agricultural frontier that cuts through the region of Jinotega. If the current deforestation rate continues, the country could lose its remaining forest cover over the course of the next two decades; therefore, it is essential that the dynamics and relationships of land-use and land-cover change (LUCC) in this region are understood. To examine LUCC in Nicaragua over time, Landsat imagery from the southern portion of the region of Jinotega, taken in 1978, 1987, and 1999 was utilized. A remote-sensing method, supervised classification, which allows for the grouping of spectrally similar values for each year, followed by an image change detection analysis (postclassification comparison) was conducted. Groundtruthing (field validation) was conducted in 2006 to validate the data, which yielded increasing overall accuracy rates of 71.68% for 1978, 82.35% for 1987, and 84.38% for 1999. The classification and change detection results showed that if the agricultural cultivation overtook this region, it happened before 1978. Therefore, the possibility that either deforestation did not actually occur along an agricultural frontier or that it was located further east exists; this would be an interesting subject for future studies. There was, however, clear evidence of increased forest cover from 1987 to 1999 near the urban center, correlating with the enforced reforestation law in the city of Jinotega.     

Multivariate analysis of trace metal levels in tannery effluents in relation to soil and water: a case study from Peshawar, Pakistan

Tannery effluents and relevant ground water and soil samples collected from various tanning industries of Peshawar were analyzed for Na, Ca, K, Mg, Fe, Mn, Cr, Co, Cd, Ni, Pb and Zn by the AAS method. The metal concentration data for the three media are reported in terms of basic statistical parameters, metal-to-metal correlations and linear regression analyses. Metal distributions in the three media were quite divergent and showed non-normal distributions with high standard deviation and skewness parameters. Sodium exhibited the highest mean levels of 1,277mg/L, 881mg/L and 12,912mg/kg in the effluent, ground water and soil samples, respectively. Among other metals, Cr concentrations were 410mg/L, 0.145mg/L, 100mg/kg and Ca, 278mg/L, 64.8mg/L, and 2,285mg/kg in the effluent, ground water and soil samples, respectively. Some significant correlations were observed between effluent and soils in terms of Na, Cr, Ni, Co and Pb. The ground water-soil interrelationship suggested that Na levels in the soil and ground water were significantly correlated with each other (r=0.486, P<0.01). Similarly, Cr in the soil is strongly correlated with Ca in ground water (r=0.486, P<0.01). These results were duly supported by the linear regression analysis of data. The source identification studies conducted using Principal Component Analysis (PCA) and Cluster Analysis (CA) evidenced that ground water and soil were being contaminated by the toxic metals emanating from the tannery effluents.