共查询到20条相似文献，搜索用时 15 毫秒
1.
Gilles Bezançon Jean-Louis Pham Monique Deu Yves Vigouroux Fabrice Sagnard Cédric Mariac Issoufou Kapran Aïssata Mamadou Bruno Gérard Jupiter Ndjeunga Jacques Chantereau 《Genetic Resources and Crop Evolution》2009,56(2):223-236
Changes in the diversity of landraces in centres of diversity of cultivated plants need to be assessed in order to monitor
and conserve agrobioversity—a key-element of sustainable agriculture. This notably applies in tropical areas where factors
such as increased populations, climate change and shifts in cropping systems are hypothesized to cause varietal erosion. To
assess varietal erosion of staple crops in a country subjected to various anthropogenic and natural environmental changes,
we carried out a study based on a comparison of the diversity of pearl millet and sorghum varieties collected in 79 villages
spanning the entire cereal-growing zone of Niger over a 26 year period (1976–2003). For these two crops, the number, name
and type of varieties according to important traits for farmers were considered at different spatial scales (country, region,
village) at the two collection dates. The results confirmed the high diversity of millet and sorghum varieties in Niger. No
erosion of varietal diversity was noted on a national scale during the period covered. Some changes were observed but were
limited to the geographical distribution of certain varieties. This highlights that farmers’ management can preserve the diversity
of millet and sorghum varieties in Niger despite recurrent and severe drought periods and major social changes. It also indicates
that rainfed cereal cropping systems in Niger should remain to be based on millet and sorghum, while reinforcing farmers’
seed systems. 相似文献
2.
Recent attempts to address land degradation have seen calls for greater integration of scientific expertise with local knowledges. In this paper we investigate the potential for such combined understandings to enhance the accuracy, coverage and relevance of land degradation assessment. We followed a participatory approach, using methods from a variety of disciplines, to elicit potential land degradation indicators from communities in Botswana and Swaziland. These indicators were then assessed according to local and scientific understandings. We noted a significant overlap between scientific and local knowledges about land degradation in most instances. Where discrepancies occurred, the integrated participatory approach we used allows appropriate explanation to be reached, supporting the case that such an iterative process can lead to both accurate and relevant monitoring of land degradation. However, the incorporation of integrated knowledges into national policy has not been widespread in either country, suggesting that much greater efforts are required to institutionalise participatory land degradation assessment methodologies. Powerful, often neo‐Malthusian narratives of degradation continue to dominate policy discourse and limit the extent to which hybrid combined local and scientific knowledges can enhance land degradation assessment on a national and regional scale. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
Land degradation is a gradual, negative environmental process that is accelerated by human activities. Its gradual nature allows degradation to proceed unnoticed, thus reducing the likelihood of appropriate and timely control action. Presently, there are few practical frameworks to help countries design national strategies and policies for its control. The study presented here developed a framework for the national assessment of land degradation. This framework is envisaged to support governments in formulating policies on land degradation. It uses time‐series remote sensing data to identify the rate and extent of land degradation, local experts to identify prevalent degradation types and drivers of the degradation and field observations to validate the overall assessment. Its simplicity, use of freely downloadable input data and self‐triangulation of the assessment methods make it suitable for rapid assessment of land degradation on a national scale. It was tested in Somalia, where it exhibited accuracy greater than 60 per cent when assessing land degradation. This framework is relevant for designing national strategies and policies that address land degradation and provides an opportunity for accurate identification of areas to target with comprehensive local assessment. Testing of the framework in Somalia showed that about one‐third of the country was degraded because of loss of vegetation cover, topsoil loss and to the decline of soil moisture. Overgrazing, excessive tree cutting and poor agronomic practices in agricultural areas were identified as the primary drivers of the country's land degradation. These drivers are encouraged by the prevailing communal land tenure practices, poor governance and civil war. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
Karst rocky desertification (KRD) is a type of land degradation especially prominent in southwest China. This article analyzes the anthropogenic driving forces of KRD at two scales: rural locality and its macro socio‐economic circumstances. At the rural locality scale, the intensive human pressure on land because of a large and fast growing population and unsustainable land use are identified to be the reason for KRD. However, more radical driving forces lie in the farmers' disadvantages in social‐economic circumstances, which compel them to overuse rural land. Hukou system, coastal development strategy, and household responsibility system are verified as three important factors in social‐economic circumstances. At last, a two‐scale framework is constructed to explain how anthropogenic driving forces lead to KRD in southwest China. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
L. C. Stringer C. Twyman D. S. G. Thomas 《Land Degradation \u0026amp; Development》2007,18(2):163-177
Maize production in Swaziland's middleveld is being increasingly threatened by the Striga asiatica weed (also called witchweed). It parasitises the maize crop to provide itself with water and nutrients, preventing the crop from growing properly. In this paper we examine the impacts of this bio‐indicator of land degradation on rural livelihoods, investigating how farmers and policy makers are responding to the problem. Our results show that farmers' ability to control weed infestations is determined by a number of environmental, social and political‐economic drivers and that national policies to reduce land degradation offer little assistance. Low‐technology methods employed by farmers are an important step in alleviating the problem, but farmers' understandings of why these methods work are limited and they often neglect to combine control strategies. At the local level, there is a need to support farmer‐to‐farmer learning and education programmes to broaden and deepen farmer knowledge about S. asiatica. At the national level a more supportive policy context is necessary that recognises weeds as an indicator of a more serious overall land degradation problem, and which uses broader criteria to determine what constitutes land degradation. Without this attention, the threat from S. asiatica could increase in both area and intensity, with profound effects on both food security and the sustainability of rural livelihoods. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
6.
Lanqing Hong Zhi-Sheng Ye Ran Ling 《Journal of Agricultural, Biological & Environmental Statistics》2018,23(3):390-409
The degradation behavior of an emerging contaminant is a key factor in its environmental risk assessment. Existing risk assessment methods based on EC degradation data commonly neglect the time-varying volatility of the degradation, the possible correlations in degradation between different ECs, and the estimation errors. To fill the gaps, this paper proposes an EC risk assessment framework based on the Wiener process. We first focus on degradation data from competitive experiments, which are adopted to evaluate a useful risk indicator, i.e., the bimolecular rate constant of a degradation reaction. A two-dimensional Wiener process model is developed to capture the degradation behaviors of the target EC and a reference contaminant in the experiment. Point and interval estimations of desired quantities, including the rate constant and the degradation half-life, are developed. We further extend the model to the multivariate case, which is applicable to waste water treatment where multiple ECs degrade in a mixed solution. A risk indicator for the mixed solution is proposed, based on which a minimal treatment time can be determined. Both point and interval estimation procedures of the risk indicator and the minimal treatment time are proposed. Two EC degradation datasets are used to demonstrate the proposed methodologies. Supplementary materials accompanying this paper appear on-line. 相似文献
7.
Aaron KK 《Journal of agricultural safety and health》2005,11(2):127-134
The Niger Delta region of Nigeria is richly endowed with both renewable and non-renewable natural resources. It contains 20 billion of Africa's proven 66 billion barrels of oil reserves and more than 3 trillion cubic meters of gas reserves. Oil and gas resources of the Niger Delta account for over 85% of the nation's gross domestic product (GDP), over 95% of the national budget, and over 80% of the nation's wealth. Paradoxically, the Niger Delta remains the poorest region, due largely to the ecologically unfriendly exploitation of oil and gas and state policies that expropriate the indigenous peoples of the Niger Delta of their rights to these natural resources. The ecological devastation occasioned by the activities of oil transnational corporations (TNCs) have rendered farming and fishing useless, previously the main occupations of these rural people. The people of the Niger Delta are deprived of their share of the wealth on which the entire nation depends; they "benefit" only from compensation for incidents of oil pollution. At the same time, occurrences of oil spills in the Niger Delta region have increased. In this article, it is argued that the ecologically unfriendly activities of oil TNCs, and the state's petroleum development policies, lead to poverty in the Niger Delta, and poverty in turn leads to environmental degradation. It is the dynamics of this interconnectedness that we wish to explore. 相似文献
8.
Soil structure and pedotransfer functions 总被引：3，自引：0，他引：3
Accurate estimates of soil hydraulic properties from other soil characteristics using pedotransfer functions (PTFs) are in demand in many applications, and soil structural characteristics are natural candidates for improving PTFs. Soil survey provides mostly categorical data about soil structure. Many available characteristics such as bulk density, aggregate distribution, and penetration resistance reflect not only structural but also other soil properties. Our objective here is to provoke a discussion of the value of structural information in modelling water transport in soils. Two case studies are presented. Data from the US National Pedon Characterization database are used to estimate soil water retention from categorical field‐determined structural and textural classes. Regression‐tree estimates have the same accuracy as those from textural class as determined in the laboratory. Grade of structure appears to be a strong predictor of water retention at ?33 kPa and ?1500 kPa. Data from the UNSODA database are used to compare field and laboratory soil water retention. The field‐measured retention is significantly less than that measured in the laboratory for soils with a sand content of less than 50%. This could be explained by Rieu and Sposito's theory of scaling in soil structure. Our results suggest a close relationship between structure observed at the soil horizon scale and structure at finer scales affecting water retention of soil clods. Finally we indicate research needs, including (i) quantitative characterization of the field soil structure, (ii) an across‐scale modelling of soil structure to use fine‐scale data for coarse‐scale PTFs, (iii) the need to understand the effects of soil structure on the performance of various methods available to measure soil hydraulic properties, and (iv) further studies of ways to use soil–landscape relationships to estimate variations of soil hydraulic properties across large areas of land. 相似文献
9.
H.&#x;J. Knig L. Zhen K. Helming S. Uthes L. Yang X. Cao H. Wiggering 《Land Degradation \u0026amp; Development》2014,25(4):385-396
The goal of China's sloping land conversion programme (SLCP) is to combat soil erosion and to reduce rural poverty. An ex‐ante assessment of possible SLCP impacts was conducted with a focus on rural sustainability, taking the drought‐prone region of Guyuan in Western China as an example. The Framework for Participatory Impact Assessment (FoPIA) was used to conduct two complementary impact assessments, one assessing SLCP impacts at regional level and a second one assessing alternative forest management options, to explore possible trade‐offs among the economic, social and environmental dimensions of sustainability. Regional stakeholders assessed the SLCP to be capable of reducing soil erosion but felt it negatively affected rural employment, and a further continuation of the Programme was advocated. Assessment of three forest management scenarios by scientists showed that an orientation towards energy forests is potentially beneficial to all three sustainability dimensions. Ecological forests had disproportionate positive impacts on environmental functions and adverse impact on the other two sustainability dimensions. Economic forests were assessed to serve primarily the economic and social sustainability dimensions, while environmental impacts were still tolerable. The FoPIA results were evaluated against the available literature on the SLCP. Overall, the assessment results appeared to be reasonable, but the results of the regional stakeholders appeared to be too optimistic compared with the more critical assessment of the scientists. The SLCP seems to have the potential to tackle soil erosion but requires integrated forest management to minimize the risk of water stress while contributing to economic and social benefits in Guyuan. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
11.
Land degradation is considered to be a major environmental problem by scientific and political institutions in Iceland. In past years, land degradation problems related to sheep and horse grazing have gradually come to the fore in public discussion of environmental questions. However, land degradation is often evaluated in different ways by different groups of people. This has led to a lack of consensus regarding rates and severity of land degradation. Therefore, it is important to study differences in environmental perception, and how these differences can be dealt with in the context of sustainable management. This paper aims to highlight farmers' perception of land degradation in Iceland, as perceptions of the environment determine the basis for human activities related to the land. A total of 100 farmers in NE Iceland were questioned and interviewed for their opinions on land degradation, its history, causes and severity. The results indicate that farmers consider land degradation to be a slow process, and not a catastrophic phenomenon. The understanding of the general ecological processes by the users affects their practices and concern for their environment. This feeds back on the land‐use system and ultimately causes changes in land‐cover. Therefore, if we are to increase our understanding of the processes that lead to land‐cover changes we have to integrate the perceptions of land users and technical experts. In this way we may improve conservation practices and land‐resource management policies. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
12.
Sustainable agricultural development in sub-Saharan Africa: the case for a paradigm shift in land husbandry 总被引：1，自引：0，他引：1
In order to tackle poverty and hunger in sub‐Saharan Africa (SSA) there is a strong case for a focus of effort on improving rainfed agricultural systems. The challenge is to deliver a transformation of agricultural productivity in such systems without adverse impacts on environmental goods and services. We examine the growing advocacy of ‘conservation agriculture’ (CA) as the desired approach and assess the evidence to support the assertion that it can deliver sustainable agricultural development in SSA. We examine in particular the evidence which derives from experience with ‘zero tillage sustainable agriculture’ in Brazil. We ask the question, is there a case for a paradigm shift in land husbandry? The case for a paradigm shift hangs on the premise that conventional practice promotes land degradation, while adoption of CA practice delivers a range of benefits through promoting soil ecosystem health. The guiding principle is to promote biological tillage through minimizing mechanical soil disturbance and maintaining permanent organic soil cover. We examine evidence of benefits in the context of the wider debate on low‐external‐input technology. We conclude that CA does not overcome constraints on low‐external‐input systems and will deliver the productivity gains that are required to achieve food security and poverty targets only if farmers have access to fertilizers and herbicides. We conclude also that widespread adoption of the new paradigm amongst millions of small farmers in order to achieve the ‘doubly green revolution’ in SSA is subject to the familiar constraints of knowledge transfer and success will depend upon creating innovation networks. Further, we conclude that amongst small‐scale farmers partial adoption will be the norm and it is not clear that this will deliver soil health benefits claimed for full adoption of the new paradigm. 相似文献
13.
B. C. Oinam W. Marx T. Scholten S. Wieprecht 《Land Degradation \u0026amp; Development》2014,25(5):483-500
Land use practices and vegetation cover distribution are considered to be the most important dynamic factors that influence the land degradation or the soil erosion of a region. In this study, a Soil Protection Index (SPI) is defined as a function of land use practices and intensity of vegetation cover. This index is used to map the relative degree of protection of topsoil from being eroded by external effects such as rainfall and overland flow. A fuzzy rule‐based model integrated within ArcGIS® has been set‐up and tested with the aim to develop SPI maps. The amount of vegetation cover distribution, that is, Normalized Difference Vegetation Index as proxy parameter and Land Use–Land Cover map are chosen as fuzzy input parameters for the SPI as the desired system output. The approach was tested in the Upper Awash basin in Ethiopia. The output SPI map was qualitatively evaluated against the expert‐defined land degradation risk class, and it was found that locations that are mapped with ‘low and very low’ SPI classes at different time periods of the year have a high potential land degradation risk. Furthermore, socio‐economic data (‘population and livestock densities’) and environmental parameters (‘altitude and soil erodibility’) for the region are used to correlate with the SPI map as an indirect method of evaluation. It is found that population and livestock density explained 68 per cent of the spatial distribution pattern of predicted SPI and an adjusted R‐squared value of 0·681 (p < 0·05) was obtained. It was also found that the SPI distribution over the region for two different time periods, that is, January and July 2001, correlated positively (R2 = 0·41 and R2 = 0·51) with the soil erodibility of the region. The transferability and applicability of the model for different environmental settings or landscapes were tested by mapping the SPI of Italy. This SPI map of Italy was compared with the soil erosion map of Italy produced by the European Soil Bureau. It can be concluded that the SPI map reflects the potential land degradation risk distribution of the case‐study region. Results show that a fuzzy rule‐based model can provide useful preliminary information even without detailed and precise data information for developing appropriate strategies for land degradation assessment vital for sustainable land use management. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
15.
A. A. Berhe 《Land Degradation \u0026amp; Development》2007,18(1):1-15
Landmines are one of the most environmentally destructive aftermaths of war facing the world today. The barely chronicled global landmine problem has transcended both humanitarian and sociological concerns to bring about environmental damage. Disruption of land's stability, pollution and loss of biodiversity constitute major ecological repercussions of landmine crisis. This review qualitatively integrates ecological, social, economic and political variables that play a role in creating and perpetuating a serious land degradation problem in landmine‐affected regions. Through a mail survey and interview with professionals working in areas related to landmines, peace research, environmental management and law and extensive archival research this review tries to unravel the many facets and causal links in the ecological and socio‐politico‐economic problems. This paper highlights the complexity of the landmine problem and interrelationships between the issues surrounding the degradation and management of landmine‐affected environments. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
16.
This paper examines the ways in which a policy aiming to improve both use of an extensive dryland natural resource, and the well‐being of rural peoples in Botswana, has impacted on the environment and upon indigenous land‐use activities. The impacts of the Tribal Grazing Land Policy (TGLP) have been spatially and temporally variable. Previous assertions about its contribution to desertification may have been overstated, although environmental changes have certainly resulted from policy impacts. Effects upon traditional indigenous population coping strategies for environmental variability are considered both in terms of subsistence activities and the ability to respond to drought events. It is concluded that the policy has not met its environmental, pastoral production or societal objectives, largely because it was founded on unestablished assumptions. Large‐scale environmental degradation and desertification, however, cannot yet be attributed to the TGLP, but it can be contended that the policy has reduced both environmental and societal resilience to natural environmental variability. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
17.
《Land Degradation \u0026amp; Development》2017,28(7):2062-2073
Large‐scale forest loss and degradation have dire consequences for biodiversity maintenance and provision of vital ecosystem services. Despite recent increasing efforts for forest restoration and sustainable management, there have been no comparative studies of biological taxonomy and multiple ecosystem functions to assess the effectiveness of forest restoration programmes, and how they vary through space and time. Here, we provided a quantitative assessment of the recovery of biodiversity and ecosystem functions by forest restoration in China using a meta‐analysis of 172 studies. We found that biodiversity and ecosystem functions were substantially increased in restored forests comparing with the degraded states. However, these restoration effects varied considerably by degradation origin, restoration approach, restoration age, ecological domains, taxonomic group and ecosystem function that is measured. Results also revealed that forest restoration from degraded states could not lead to full recovery of biodiversity and ecosystem functions, highlighting the irreplaceability of primary forests. We advocate allowing for natural or passive recovery, especially where biophysical conditions are favourable for spontaneous succession, or too harsh for human‐aided restoration, and choosing a combination of passive and active restoration measures based on adaptive management strategies. Our meta‐analysis provided fundamental insights into bridging the gap between small‐scale experiments and broad‐scale management needs towards highly effective and sustainable forest ecosystem restoration. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
18.
Hydrological extremes are major weather related disasters, but little is known about their long‐term patterns in the context of environmental change. Better understanding of damaging rainfall (e.g. rainfall‐erosivity events) occurring at different time‐scales has important implications for hydrological and land degradation management. The study of the interdecadal variations may help in understanding some of the consequences of abrupt environmental changes over long time periods. Thus, a decadal‐scale rainfall erosivity model (DREM), comparable with the Revised Universal Soil Loss Equation (RUSLE), was developed based on a parsimonious interpretation of rain aggressiveness (95th percentile of rainfalls). The DREM was parameterised to capture interdecadal erosivity variability at the Ukkel station (Belgium), which has the longest RUSLE‐based rain‐erosivity series in Europe (1898–2007). The DREM performed well against decadal RUSLE data, with a coefficient of determination (R2) of 0·72 and a Nash–Sutcliffe efficiency index of 0·71. The model outperformed three well‐established models used in this study (R2 ~ 0·4). For a spatial evaluation of the DREM, a pattern of decadal rainfall erosivity was provided for an area around Ukkel, which includes the western part of Germany bordering Belgium, and was compared with maps from the RUSLE approach for 1961–1990. The 95th percentile of June–September rainfalls proved to be a better predictor of decadal rainfall erosivity than yearly based precipitation amount. These results lay the foundation for estimating decadal erosivity in the surrounding areas of Ukkle as well as for historical reconstructions where detailed hydrological data are unavailable, and assumptions cannot be met, for physically based models. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
Degradation of isoproturon in earthworm macropores and subsoil matrix—a field study The objective is to compare the time scale of microbial degradation of the herbicide Isoproturon at the end of earthworm burrows with the time scale of microbial degradation in the surrounding soil matrix. To this end, we developed a method which allows the observation of microbial degradation on Isoproturon in macropores under field conditions. Study area was the well‐investigated Weiherbach catchment (Kraichgau, SW Germany). The topsoil of a 12 m2 large plot parcel was removed, the parcel was covered with a tent and instrumented with TDR and temperature sensors at two depths. After preliminary investigations to optimize application and sampling techniques, the bottom of 55 earthworm burrows, located at a depth of 80–100 cm, was inoculated with Isoproturon. Within an interval of 8 d, soil material from the bottom of 5–6 earthworm burrows was taken into the laboratory and analyzed for the Isoproturon concentration for investigation of the degradation kinetics. Furthermore, the degradation of Isoproturon in the soil matrix, that surrounded the macropores at the field plot, was observed in the laboratory. Microbial degradation of Isoproturon at the bottom of the earthworm burrows was with a DT‐50‐value of 15.6 d almost as fast as in the topsoil. In the soil matrix that closely surrounded the center of the earthworm burrows, no measurable degradation was observed within 30 d. The clearly slower degradation in the soil matrix may be likely explained by a lower microbial activity that was observed in the surrounding soil matrix. The results give evidence that deterministic modeling of the fate of pesticides once transported into heterogeneous subsoils by preferential flow requires an accuracy of a few centimeters in terms of predicting spatial locations: time scales of microbial degradation in the subsoil drop almost one order of magnitude, in case the herbicides dislocates from the bottom of an earthworm burrow a few centimeter into the surrounding soil matrix. If at all, predictions of such an accuracy can only be achieved at locations at sites where the soil hydraulic properties and the macropore system are known at a very high spatial resolution. 相似文献
20.
Crossing the thresholds: human ecology and historical patterns of landscape degradation 总被引：2，自引：0，他引：2
In discussions of landscape sensitivity, human activities have generally been regarded as external forces contributing to landscape change, with a focus on the impacts of cultivation methods, fertiliser practices, grazing pressures and atmospheric pollution. However, there has been comparatively little study undertaken that integrates physical and social systems in a historic context to explain the basis of human activity in sensitive landscapes. Where such attempts have been made, the manner of common land management has figured prominently, with ‘tragedy of the commons’ concepts used to explain land degradation and to provide a foundation for policy response. This has also been the case in Southern Iceland and in this paper we assess the extent to which common land domestic grazing pressures were the primary external force causing soil erosion and land degradation during the period of occupation from ca. 874 AD. We first provide field observation of soil erosion, temporally defined by tephrochronology, to highlight the extent of land degradation during this period. The ‘tragedy of the commons’ explanation of degradation is then assessed by evaluating historic documentary sources, and by environmental reconstruction and modeling of historic grazing pressures. These analyses indicate that regulatory mechanisms were in place to prevent overgrazing from at least the 1200s AD and suggest that there was sufficient biomass to support the numbers of domestic livestock indicated from historic sources. We suggest that failure to remove domestic livestock before the end of the growing season and an absence of shepherding were more likely to contribute to land degradation than absolute numbers. Lack of appropriate regulation of domestic livestock on common grazing areas can be attributed to limited cultural knowledge of changing and rapidly fluctuating environmental conditions. 相似文献