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1.
T. P. Burt 《CATENA》2001,42(2-4)
Until recently, ‘land use’ was regarded as a single function: in rural areas of the UK this simply meant ‘farming’ or, in the uplands, ‘forestry’. However, there is now growing recognition of the multiple use of land, and farming or forestry must compete with other functions, in particular water supply. Links between hydrological pathways and stream water quality are described as a context for understanding the transport of pollutants to the river system. The concept of landscape sensitivity is then described and applied to the topics of soil erosion and nitrate leaching. Based on these analyses, guidelines for integrated management of sensitive catchment systems are proposed. 相似文献
2.
I. Scoones 《Land Degradation \u0026amp; Development》1992,3(2):99-113
This paper considers evidence of land degradation and its impact on livestock production systems in the communal areas of southern Zimbabwe. Various measures of rangeland degradation, using both primary and secondary production indicators, are examined. An apparent contradiction emerges between the high observed levels of soil erosion and the lack of impact on livestock production, as measured by population density trends, cattle production parameters, cumulative stocking levels and extraction rates. Farmers' observations of land degradation processes support the quantitative data. A possible resolution of the contradiction lies in an assessment of the spatial and temporal dimensions of degradation patterns; this points to the fact that current erosion is concentrated in areas that are not key grazing resources for cattle. The analysis suggests an agenda for degradation research that concentrates on evaluating the time span over which economic impacts of soil erosion are felt and assessing the spatial pattern of soil loss, with a special focus on key grazing resource patches. 相似文献
3.
There has been increasing interest in potential benefits to be gained by restoring damaged peatlands, with the majority of funding currently being driven by the recovery of protected habitats. However, few data are available linking vegetation community declines with peatland drainage, and so the potential for recovery remains difficult to predict. Surprisingly, there is a similar paucity of research demonstrating the extent of drainage impacts on grazing conditions for livestock, despite this being a priority amongst land managers. We attempt to address these two knowledge gaps, first by investigating whether ditches in blanket bog habitat have improved or increased grazing for sheep, and second by assessing the impact of ditches on the condition of vegetation communities. At an extensively drained upland blanket bog in Wales, currently undergoing ditch blocking restoration, we collected vegetation and sheep occurrence data across five catchments and over 2 years. We present evidence that drained areas had remained relatively wet and were less preferred by sheep. Furthermore, our results show that while sheep preferred graminoid-rich areas, drainage did not increase the abundance of this species group. Drainage at the site has, however, resulted in some degradation in blanket bog vegetation adjacent to ditches; although at the landscape scale, historic high grazing levels appear to explain much of the current poor ecological condition of the site. We conclude that drain-blocking restoration should not reduce sheep grazing conditions beyond their current relatively poor state, and thus in this respect may not represent a threat to hill farming productivity. 相似文献
4.
Land degradation is not uniform, even in the same landscape, but nevertheless an overall consensus seems to grow on the fact that many areas are under way of rehabilitation. It is a debateable question whether the improving areas are improving because of interventions—or whether this has more to do with processes of innovation and adaptation. The international symposium ‘HighLand2006’ on land degradation and land rehabilitation, held in Mekelle (Ethiopia), from 21 to 25 September 2006, created a forum for those conducting research in East African Highlands as well as in similar regions around the globe to discuss findings. Tropical highlands (>1000 m a.s.l.) cover 4.5 million km2 with an average population density of 33 inhabitants km−2. Nearly all tropical highlands suffer from land degradation, especially medium to very high water erosion. Exchange of experiences during in-door sessions and excursions led to results which are condensed in this special issue. Studies presented tend to invalidate hypotheses on irreversibility of land degradation in tropical mountain areas. Circumstances are that in highly degraded environments, with high pressure on the land, no other alternatives are left open but to improve land husbandry; and that this is particularly successful in places where decision making processes at different levels in society give the highest priority to the implementation of soil and water conservation and other land rehabilitation, in situ and at catchment level. 相似文献
5.
Within the European Union (EU)-funded Project ‘Wind Erosion on European Light Soils’ (WEELS), a model was designed and implemented with the aim of predicting the long-term spatial distribution of wind erosion risks in terms of erosion hours and wind-induced soil loss. In order to ensure wide applicability, the model structure consists of a modular combination of different approaches and algorithms, running on available or easily collected topographic and climatological data input. Whereas the ‘WIND’, ‘WIND EROSIVITY’ and ‘SOIL MOISTURE’ modules combine factors that contribute to the temporal variations of climatic erosivity, the ‘SOIL ERODIBILITY’, ‘SURFACE ROUGHNESS’ and ‘LAND USE’ modules predict the temporal soil and vegetation cover variables that control soil erodibility. Preliminary simulations over a 29-year period for the Barnham site (UK) (1970–1998) and a 13-year period for the Grönheim site (Germany) (1981–1993) generally resulted in a higher erosion risk for the English test site, where the total mean soil loss was estimated at 1.56 t ha−1 year−1 and mean maximum soil loss at about 15.5 t ha−1 year−1. The highest rates exceeded 3 t ha−1 in March, September and November. On the northern German test site, the total mean soil loss was 0.43 t ha−1 year−1. The highest erosion rates were predicted in April when they can exceed 2.5 t ha−1. The total mean maximum soil loss at this site of about 10.0 t ha−1 year−1 corresponds to a loss of about 0.65 mm. Predictions based on a land use scenario for the German site revealed that the erosion risk could be reduced significantly by changing land use strategies. 相似文献
6.
Javier lvarez‐Martínez Amelia Gmez‐Villar Teodoro Lasanta 《Land Degradation \u0026amp; Development》2016,27(1):3-13
Spanish mountains have been affected by the expansion of shrubs and forests since the mid‐20th century. This secondary succession in vegetation has some positive effects, but also drawbacks, such as an increase in fire risk, loss of diversity in land use, a reduction in landscape and cultural value, less water available in river channels and reservoirs, constraints on livestock farming, a reduced number of local species and loss of biodiversity. This paper analyses the potential for grazing domestic goats to help control the spread of several species of shrubs such as the common broom (Cytisus scoparius), red raspberry (Rubus idaeus) and roses (Rosa sp.) that are commonly found in degraded pastures in the Cantabrian Mountains of northern Spain. Using experimental plots, the effects of two levels of stocking density (4·5 and 9 goats ha−1 y−1) are compared with other land management systems used in the region: burning, mechanical clearing and trimming. The combined use of goats with support from burning, clearing and trimming controls the spread of shrubs. The most efficient treatment was found with nine goats ha−1 y−1. Goat grazing also changes the distribution of shrubs, transforming a dense and continuous coverage into separate clumps and thereby enabling livestock to graze more easily. Maintaining a mixed structure of shrubs and pastures is the best treatment due to the low population density of the Cantabrian Mountains, as this enhances the biodiversity, controls fire risk and enriches the landscape; it also allows extensive livestock grazing as a main economic resource. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
In the Thar (Rajasthan) Desert of India, sand dunes and sandy plains dominate the landscape. Livestock raising and marginal land cultivation are the main occupations. Owing to the high growth rates of human and livestock populations and a decrease in pasture area and its primary productivity, these lands bear acute grazing pressure. Average rainfall is low and vegetation growth is restricted to the short rainy season of two to four months duration. Often there are years of lower than normal rainfall. In these circumstances, fenced areas, established to stabilize formerly active sand dunes, are increasingly opened to grazing to prevent high stock mortality during droughts. This study was conducted in four fenced and one open site, representative of the region's different vegetation types and grazing pressures. The impact of 2 and 5 per cent free grazing pressure on protected sand dune vegetation density and cover was tested in the two fenced sites. The vegetation data for grazed sites are compared with those for the two ungrazed fenced (protected) and one unfenced (open) site subjected to unlimited grazing pressure throughout the year. The vegetation sampling was carried out by the qaudrat and line-transect method before and after grazing from November 1984 to October 1986. It shows a significant reduction in the density and cover of many palatable species and an increase of unpalatable plants. The effect of vegetation degradation is greater in the unfenced area. The low grazing pressure on the fenced sand dunes sites can still cause drastic changes in the vegetation density and cover. Protection resulted in reduced sand erosion and enhanced growth of palatable plants in the fenced sites under similar climatic and edaphic conditions to the unfenced sites. The grazing pressure in the unfenced areas remains high to extreme during the year, due to low land productivity and high feed demand. The regeneration rate is very slow under the constant (3rd to 5th degree) overgrazing. Low intensity grazing pressure on the fenced sites during droughts can cause heavy utilization and mortality of palatable vegetation. 相似文献
8.
新疆天山东段南北坡土壤侵蚀调查 总被引：1，自引：0，他引：1
[目的]开展新疆维吾尔自治区天山南北坡土壤侵蚀调查,研究该区土壤侵蚀特征和影响因子,以期为该区域水土流失防治提供科学依据。[方法]在新疆天山东段南北坡选取了14个调查单元,于2019年6月25—30日,对调查单元内的土壤侵蚀类型与特征、土地利用类型和植被生长状况等进行了调查。[结果]天山南北坡土壤侵蚀主要发生在草地和开发建设项目区。草地整体退化严重,放牧导致鳞片状侵蚀和羊道侵蚀广泛存在,局部区域发生剥蚀、掏蚀和重力侵蚀。开发建设项目防护措施较少,侵蚀表现形式以堆积体沟蚀为主。[结论]过度放牧导致研究区草地生态系统恢复缓慢,开发建设项目对原生态系统的破坏,引起了严重的人为加速侵蚀,严重威胁天山区域的生态安全。在该区域迫切需要开展土壤侵蚀基础数据的监测与研究,加大水土保持工作力度,建立合理的放牧制度,加速生态系统恢复速度,减少水土流失,保障天山地区生态安全和健康发展。 相似文献
9.
Romina G. Palacio Alejandro J. Bisigato Pablo J. Bouza 《Land Degradation \u0026amp; Development》2014,25(6):594-603
Grazing has been identified as the main cause of land degradation in Patagonia. However, land degradation is highly variable among areas, even within the same paddock. This strongly suggests that different plant communities differ in their resistance to land degradation. In this study, we have evaluated soil erosion at both microsite and community scales in coexisting plant communities subject to sheep grazing in northeastern Patagonia. Three plant communities coexist in the area: two shrub steppes dominated by Chuquiraga avellanedae Lorentz and Nassauvia ulicina (Hook. f.) Macloskie, and a grass steppe dominated by Nassella tenuis (Phil.) Barkworth. At a community scale, our results indicate that shrub steppes generally experienced soil erosion, whereas the grass steppe commonly did not show signs of soil erosion/deposition. At a microsite scale, non‐vegetated soil surface types and degraded mounds never accumulated sediments, regardless of plant community. In contrast, we found that in some sites, the intact mounds and grasses entrapped sediments, but in other sites, soil erosion prevailed. Our results highlight the fact that soil erosion measurements are scale dependent, because results at microsite and community scales often differ. When comparing among communities, grass steppe is more intensely grazed, but at the same time, it shows less evidence of past and present erosion. In contrast, the N. ulicina community showed a direct relationship between grazing and soil erosion. Finally, soil erosion was not related to grazing in the C. avellanedae community. Our results demonstrate that the grass steppe is more resistant to land degradation than shrub steppes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
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 scientific 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. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
11.
Influences of continuous grazing and livestock exclusion on soil properties in a degraded sandy grassland, Inner Mongolia, northern China 总被引：10，自引：0，他引：10
Overgrazing is one of the main causes of desertification in the semiarid Horqin sandy grassland of northern China. Excluding grazing livestock is considered as an alternative to restore vegetation in degraded sandy grassland in this region. However, few data are available concerning the impacts of continuous grazing and livestock exclusion on soil properties. In this paper, characteristics of vegetation and soil properties under continuous grazing and exclusion of livestock for 5 and 10 years were examined in representative degraded sandy grassland. Continuous grazing resulted in a considerable decrease in ground cover, which accelerates soil erosion by wind, leading to a further coarseness in surface soil, loss of soil organic C and N, and a decrease in soil biological properties. The grassland under continuous grazing is in the stage of very strong degradation. Excluding livestock grazing enhances vegetation recovery, litter accumulation, and development of annual and perennial grasses. Soil organic C and total N concentrations, soil biological properties including some enzyme activities and basal soil respiration improved following 10-year exclusion of livestock, suggesting that degradation of the grassland is being reversed. The results suggest that excluding grazing livestock on the desertified sandy grassland in the erosion-prone Horqin region has a great potential to restore soil fertility, sequester soil organic carbon and improve biological activity. Soil restoration is a slow process although the vegetation can recover rapidly after removal of livestock. A viable option for sandy grassland management should be to adopt proper exclosure in a rotation grazing system in the initial stage of grassland degradation. 相似文献
12.
Landscape analysis of dynamic soil erosion in Subtropical China: A case study in Xingguo County, Jiangxi Province 总被引：1，自引：0，他引：1
K. Wang H.J. Wang X.Z. Shi D.C. Weindorf D.S. Yu Y. Liang D.M. Shi 《Soil & Tillage Research》2009,105(2):313-321
As a case study on landscape pattern analysis of soil erosion change, Xingguo County in Jiangxi Province, China, was once one of the most severely eroded regions in Subtropical China. However, its soil erosion has been completely controlled in recent years. This county was historically full of forest as well as waterways that were well protected and soil erosion was seldom seen even by the mid-19th century. However, large areas of forest were destroyed after that period due to over-logging, which resulted in excessive erosion, bare hills, and mountains devoid of vegetation. Fortunately, soil erosion in Xingguo has been controlled gradually since 1982 after the county was appointed as 1 of the 8 Key National Level Erosion Control Regions. In this study, a raster (grid) soil erosion map was collected on the basis of soil erosion intensity maps from 1958, 1975, 1982 and 2000 with the aid of GIS software (ARC/INFO). Over 10 landscape indices were calculated using FRAGSTATS software for landscape pattern analysis. A set of free spatial statistics that address a fundamental problem in GIS, and soil erosion distribution patterns and their changes in the county were quantitatively analyzed at the landscape and class levels, respectively. Moreover, transformations of soil erosion types from 1958 to 1975, 1975 to 1982, and 1982 to 2000 were also calculated using the CROSSTAB module in IDRISI software. Results showed that at the landscape level, heterogeneity of soil erosion decreased. This was supported by decreasing tendencies of patch indices SHDI (Shannon’s diversity index), SHEI (Shannon’s evenness index), and IJI (Interspersion and juxtaposition index). This indicates that most of the severely eroded soil types were transformed into non-apparently eroded or slightly eroded types. Meanwhile, at the class level, a consistent pattern was found where the surface areas of non-apparently eroded or slightly eroded lands increased, and moderately, severely, very severely and extremely eroded lands deceased. In general, soil erosion in Xingguo County experienced three pronounced phases during the study periods: the exacerbation phase (1958–1975), the alleviation phase (1975–1982), and the overall alleviation phase (1982–2000). By the year 2000, 74.6% of total territory of this county was covered by land with no significant soil loss, indicating that severe soil erosion had been substantially controlled. 相似文献
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A landscape integrated survey was carried out on the badlands area in the Upper Orcia River Valley (Siena, Italy). A methodology has been investigated to explain the soil response to dynamic and anthropic factors from an erosion hazard point of view.The Upper Orcia River Valley is one of the many neogenic basins linked to the Pliocene sea ingression, in Tuscany and all over Italy. Sediments are mainly fine silty-clay and the region is characterized by an estensive net of joints, faults and fractures due to the neotectonics in the area. The area is undergoing a fast land degradation characterized by “biancane” (domes), “calanchi” (very steep and deep gullies with a typical dendritic drainage net), gullies, several surficial erosional forms and mass movement phenomena (creeping, landslides, solifluctions and anthropic levelling).Seventeen Land Units and 46 Types were recognized according to the relationships between Elementary Landform and slope (EL), Hydrographic Net Patterns (HNP), River Bed (RB), Geomorphic Dynamics (GD), Erosion Forms (EF), Mass Movements (MM), vegetation and land use (VLU), Cultural Management systems (CM) and Morphological Sequences (MS). Lithology and soils were not taken into account as the former is to be considered almost homogeneous, while the latter are of the Entisols and Inceptisols orders (Soil Survey Staff, 1975) in the Typic Xerorthent and Xerochrept Subgroups. The soil pattern is mainly linked to geomorphic dynamics and appears extremely leopardized, every landform being characterized by various toposequences.PCA and clustering based on Euclidean distance (similarity measure) were utilized. A normalization of the variables to the standard deviation of the population was used. The previous PCA and Varimax rotation reduced the number of the variables from the original 9 to the 5 more weighing ones (1-2-5-6-7). Clusters were created to verify the Land Types groups as well as the possibility of unifying Land Units with the higher similarity level. The cluster analysis resulted in 15 groups that can well explain different land degradation patterns and which, in some cases, confirmed the Land System Analysis. The Authors came to the conclusion that multivariate analysis of landscape characteristics can only partially substitute the landscape integrated survey but can be considered a helpful means to analyse the distribution in the area of mass movements and erosion phenomena. 相似文献
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The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike peninsula was once supplied with fertile soils, in large areas desertification takes place today. Detailed analysis of soil profiles allowed the reconstruction of the history and of causes and effects of soil erosion and gullying in the context of land use history and cultural evolution. The results of the stratigraphic analysis prove that from the beginning of human settlement around AD 300/600 until AD 1280 the agriculture on Poike peninsula was characterised by sustainable land use and a traditional type of agro-forestry. Soil erosion was not significant. At around AD 1280 the woodland on Poike, dominated by the endemic palm Jubaea sp., was cleared by slashing and burning. Intensive farming on the upper slopes of the volcanic peninsula resulted in sheet erosion lasting until the 20th century. Settlements and ceremonial places which were built around AD 1300 on downslope areas were buried soon by sediments. Agriculture ceased around AD 1400 on downslope areas as the fertile soils were completely eroded. From AD 1400 until the late 19th century sheet erosion and the accumulation of fine-layered sediments migrated upslope. On average 8.6 Mg of soil per hectare and per year were reworked by erosion (eroded and accumulated within the catchment). Gullying began on Rapa Nui with the sudden increase in the number of sheep during the early 20th century. Gullies are still developing on the island and their ongoing enlargement created extended badlands on Poike which pose a significant problem for ecological and archaeological conservation strategies. Gullying rates exceed 190 Mg ha− 1 y− 1. 相似文献
17.
《Land Degradation \u0026amp; Development》2017,28(1):46-56
Soil degradation is globally concerning due to its adverse effects on the environment and agricultural production. Much of Swaziland is at risk from degradation. This paper assesses farmer perceptions and responses to soil degradation in 2002 and 2014, focusing on two land uses that underpin rural livelihoods: arable land and rangeland areas. It uses repeat household surveys and semi‐structured interviews, in two case study chiefdoms in the country's middleveld (KaBhudla and Engcayini) in the first longitudinal study of its kind. We find that observations of land degradation are perceived mainly through changes in land productivity, with chemical degradation occurring predominantly on arable land and physical degradation and erosion mainly in rangeland areas. Changes in rainfall are particularly important in determining responses. While perceptions of the causes and impacts of degradation largely concur with the scientific literature, responses were constrained by poor land availability, shorter and more unpredictable cropping seasons because of changing rains and low awareness, access to or knowledge of agricultural inputs. We suggest that sustainable arable land management can be enhanced through improved access to alternative sources of water, use of management practices that retain soil and moisture and greater access to agricultural inputs and capacity building to ensure their appropriate use. We suggest collaborative management for settlement planning that integrates soil conservation and livestock management strategies such as controlled stocking levels and rotational grazing could improve land quality in rangeland areas. Together, these approaches can help land users to better manage change. © 2016 The Authors. Land Degradation & Development published by John Wiley & Sons Ltd. 相似文献
18.
Nicholas J. Georgiadis J.G. Nasser Olwero Gordon Ojwang’ 《Biological conservation》2007,137(3):461-472
Ecosystem processes in African savannas can be better conserved if management is based on a mechanistic understanding of wildlife dynamics in livestock-dominated landscapes. For Laikipia District, a non-protected savanna region in northern Kenya, we used spatially explicit estimates of density to characterize factors influencing the dynamics of large herbivores on three land-use types: commercial ranches that favor wildlife, communal ‘group ranches’ practicing pastoralism, and the remainder (‘transitional’ properties). For 21-year time series of nine wild and two domestic species, linear model selection was used to ascribe between 45% (Grant’s gazelle) and 95% (plains zebra) of observed variation in biomass density to land use, rainfall-dependence, density-dependence, and trends over time.Strongly opposing patterns of variation across the landscape in wildlife and livestock densities affirmed the primacy of land use among factors influencing wildlife abundance in non-protected areas. Rainfall limited densities of only the dominant grazing species throughout the monitoring period (plains zebra and cattle), and of most other species while their densities were high. Regulating effects of density were detected only for the dominant wild grazing and browsing species (zebra and giraffe). All but two wild species (zebra and Grant’s gazelle) declined on at least one land-use type, for reasons that varied among land uses.Where favored, diverse and abundant wild herbivores (mean of 1.7 t km−2 on pro-wildlife ranches) can thrive even when sharing the landscape with a slightly higher biomass density of livestock (mean of 2.7 t km−2). Where not favored, only a few resilient wild species (e.g. gazelles and plains zebra) persist with high densities of livestock (mean of 4.6 t km−2 on transitional ranches). Maintaining higher wild species diversity in the landscape will depend on the creation of a network of unfenced conservation areas in which livestock densities are persistently low or zero, which are sufficiently large to act as ‘sources’ of wild species that are prone to displacement by humans and livestock, and which generate benefits to community members that exceed opportunity costs. 相似文献
19.
Sand dunes form one of the most fragile terrestrial ecosystems. in Rajasthan they have a diverse vegetation and are often utilized by considerable human and livestock populations. a thorough knowledge of the resource utilization by the human and animal populations is essential if the future potential of the ecosystem and its physical stability under changing environmental conditions are to be accurately assessed. This study examines the socio-economic aspect of land degradation at four sites in Churu and Jhunjhunu districts, northwest Rajasthan. an attempt is made to assess the socioeconomic factors leading to land degradation. Data on human use of the Rajasthan (Thar) Desert semiarid ecosystem were collected through individual interviews, group discussions and field measurements. the present exploitation of soil and vegetation resources, possible future biomass deficiency, its impact on sustainable development and role in land degradation are examined. The average number of people in each household in the study area, and the number of livestock each household maintains are too high to allow a satisfactory income to be sustained. the annual income of 50-90 per cent of households was less than 10 000 rupees ($US 1 = 17 rupees in 1987). Sale and consumption of milk, wool, surplus animals and wood provide livelihood, supplemented with income from wage labour. Rain-fed marginal land cultivation produces poor yields and the per capita production is too low to justify the huge soil erosion losses occurring. the number of goats, sheep and cattle owned by the inhabitants has increased tremendously in recent years. Stocking rates vary from 1.63 to 12.08 animals per hectare. the grazing pressure during the dry season, when forage availability decreases, reaches 34.9 animals per hectare. as a result of overgrazing, The land productivity has decreased considerably. the annual fodder deficit values in the study area are enormous. Demand for fuelwood at all the study sites is increasing, yet available forests have already largely been cut down. the distance travelled to collect fuelwood has been increasing, whereas the amount and quality of fuelwood is decreasing. Use of cattle dung to supplement fuelwood during the summer dry season and in drought periods has been decreasing due to low fodder availability and high livestock mortality. Human numbers are increasing, and livestock numbers are also multiplying (except in drought periods) and consequently the available resources are decreasing. Soil erosion and desertification will continue to increase during the next decade unless effective counter measures are undertaken. 相似文献
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