High resolution paleoenvironmental and chronological investigations of Norse landnám at Tasiusaq, Eastern Settlement, Greenland

High-resolution paleoenvironmental data from a peat profile with a small pollen source area are used to reconstruct the impacts of landnám on vegetation and soils at a Norse farm complex (∅2 at Tasiusaq) comprising two farms in the Eastern Settlement of Greenland. Analyses include the AMS ¹⁴C dating of plant macrofossil samples and the use of Bayesian radiocarbon calibration to construct improved age-depth models for Norse cultural horizons. The onset of a regional landnám may be indicated by the clearance of Betula pubescens woodland immediately prior to local settlement. The latter is dated to AD 950-1020 (2σ) and is characterised by possible burning of Betula glandulosa scrub to provide grassland pasture for domestic stock. Clearance and grazing resulted in accelerated levels of soil erosion at a westerly farm. This was followed by an easterly migration of settlement and agriculture. Site constraints prevent an assessment of the demise of the easterly farm, but pressures of overgrazing and land degradation may have been the major factors responsible for the abandonment of the earlier farm.     

Soil erosion, policy and people's perceptions in a rural community in KwaZulu-Natal, South Africa

In South Africa the science and practice of soil conservation have been dominated by a technical approach which does not take into account the perceptions, knowledge and needs of people living in rural areas. Attempts to incorporate land users into soil conservation programmes have not had much influence on conservation policies. In order to compare the scientifically-based physical appraisals of an area with the community's perceptions of soil erosion on their land, a project was established in a rural area of KwaZulu/Natal. This paper briefly reviews soil conservation policy in former homeland areas. It then considers the historical development of the community of Cornfields and their responses to changing government policies. The research indicates that rural dwellers have valuable knowledge concerning soil conservation, but that the neglest of such communities by agricultural and conservation authorities has led to the unsustainable use of the land. The area is severely eroded and soils in the area are amongst the most highly erodible in the province. Therefore levels of degradation would be high even without dense human occupation. This evidence is clearly important in future conservation planning and recommendations are made regarding a policy for the management of soil resources in rural areas.     

Human impact on the karst of the Venetian Fore-Alps, Italy

People have been exploiting the limestone massifs of the Venetian Fore-Alps since prehistory. The fluviokarstic style of the relief and the location of springs were important controls of settlement and land use. Six principal types of exploitation are recognized and overlapped in time: (1) hunting and early farming, Paleolithic to Iron Age, with the first soil erosion; (2) general deforestation for timber, charcoal, and fuel, Roman to early modern; (3) farm enclosure and improvement, with stone clearing, medieval to modern; (4) trench warfare in World War I; (5) quarrying and specialized farming (dairy, poultry, pigs) since 1950; and (6) developmnent of modern summer and winter tourist facilities. Soil erosion effects from many centuries can still be recognized, war damage remains visible and continues to pollute aquifers, and modern pressure on the karst land and water resources is often severe.     

Conservation status of wetlands in Zimbabwe: past and present

The conservation status of dambos, a particular type of wetland associated with the headwaters of rivers draining the central plateau area of Zimbabwe, is examined in terms of past and present utilisation and erosion problems. Pre- and post-1950 phases are recognized within both the commercial farming areas and the Communal Lands (or peasant farming areas). The pre-1950 phase on commercial farms was one of exploitation of dambos mainly for winter wheat production, such cultivation contributing towards locally serious erosion. Consequently legislation was passed to restrict disturbance of wetlands, especially for cultivation. The post-1950 phase on commercial farms was one of conservation, with minimal use of dambos for grazing and limited erosion. The pre-1950 phase within the Communal Lands, the former native reserves, was one involving progressive modification of the traditional farming system through, in particular, centralisation. Dambo cultivation, a well-established practice, continued throughout this place, but towards the end of this period there were localised signs of degradation associated, in part, with grazing. The post-1950 phase was one of increased pressure on land with a growing human and livestock population. Thus dambos were required to support more and more cattle throughout the year, whilst efforts to curtail dambo cultivation were not well-recieved by peasant farmers and may have compromised general conservation in the reserves.     

Pollen evidence of vegetational change following early European settlement of Monhegan Island, Maine, northeastern U.S.A.

Postsettlemcnt vegetation changes beginning in the early 17th century were studied through comparing stratigraphic peat-pollen data with available historical evidence. The isolation of the site and the relatively long historical record were ideal for the study. Human disturbance of the vegetation was readily identified in the pollen diagram with a contemporaneous increase in sediment mineral matter. The effects were much the same as the changes associated with Neolithic forest clearance in Northern Europe. Settlement resulted in the introduction and expansion of several cultural weeds after grazing and cultivation of Zea mays began on the island in the first decades of the 17th century; Rumex acetosa-acetosella, Ranunculus acris type, Plantago major-media and several new Compositae and Umbelliferae species all appeared at that time. The response of the native species to settlement was varied. Because of the limitations of the palynologic method, the area of cultivated land and detailed kind of agriculture can only be estimated. The data suggest that although agriculture was intensive from time to time, it took place on a very limited local scale; fires, grazing, and lumbering were the major factors affecting natural ecosystems.     

Assessment of erosion damage in Ndome and Ghazi, Taita Taveta, Kenya: Towards an integrated erosion management approach

Aerial photograph interpretation on erosion trends from 1961 to 1998 showed that by 1998, approximately 17 and 50% of agricultural land in Ndome and Ghazi respectively had been permanently lost due to the combined effect of rill, inter-rill, and gully erosion, and sand deposition. Although abnormally heavy rains received between 1996–98 caused much of the present land damage, the severity of the damage was enhanced by inappropriate and persistent human perturbations in the land-system notably through vegetative degradation and destruction of soil structure through inappropriate tillage practices. With soil organic matter contents of 1.6 and 1.9%, and clay ratios of 10.1 and 10.6 for Ndome and Ghazi, respectively, the areas inherent erodibility was considered as high thus pointing to the need for careful use and management of the soil resource. That farmers appreciated only land quality indicators that were visible to the naked eye and that directly affected their subsistence, revealed a knowledge gap that saw damages from intrinsic processes like rill and inter-rill erosion proceed unnoticed. This paper argues that the spread of erosion damage in rural agro-ecosystems is survival-driven. And as a remedy to this problem, there is need for the diversification of livelihood endeavours to alternative off-farm income sources to reduce pressure on the already fragile land resource. Further, being the ultimate implementers of conservation technologies and by virtue of the multiplicity and inter-relation of rural household needs, adoption of an integrated erosion management approach with food security as paramount presents the most practical entry point for sustainable land management in such rural agro-ecosystems. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国历史耕地变化及其对自然环境的影响*

农业开发已经直接或间接地影响并正在影响自然环境的许多方面,中国农业开发历史悠久,对自然环境造成的影响广泛而强烈,对认识人类活动导致的全球与区域环境变化具有代表性。文中总结了近年来基于考古和历史文献记录的中国历史耕地变化定量重建和耕地开发环境影响的研究成果。主要结论包括: (1)中国在历史耕地变化重建方面具有独特的优势,主要数据源包括田亩、税赋、人口等与耕地数量相关的数值记录,考古遗址点、聚落、路网、行政建制等与农业活动相关的信息,有关土地开发和农业生产的描述性记录等三大类。 (2)对全国尺度的耕地面积推断始于春秋战国时期,过去1000年以来已重建了省(路)域的垦殖率,过去300年基于历史记录重建的东北、华北等区域垦殖率的分辨率已到县,在重建基础上利用分配模型获得的过去300年格网化垦殖率的分辨率可达10 km×10 km甚至1 km×1 km。相比于当前广泛使用的国际数据集,这些区域定量重建结果更为准确。(3)历史时期中国耕地的3次大规模扩张分别主要出现在西汉、两宋和清中叶,与此相对应,植被破坏和水土流失从北方地区扩展到南方地区,从平原低地扩展到低山丘陵、深山地区;过去300年耕地变化导致了碳排放的增加和可辨识的区域气候变化。未来中国的历史耕地变化重建及其对环境影响研究,应与国际过去土地利用/覆盖研究衔接,研究重点为延长历史耕地重建时限、提高重建单元的空间分辨率和改进耕地格网化分配模型。     

Nebkha development and its relationship to environmental change in the Alaxa Plateau,China

Extensive nebkha areas develop mainly under the control of aeolian processes, and their sediments record information on regional environmental changes during different periods. Such areas have developed on the dry riverbeds and deserted arable lands of China’s Alaxa Plateau, Taklimakan, and Kumutage deserts. In this paper, we studied nebkhas that had developed in the Heicheng–Juyan region to determine their CaCO₃ contents, particle size distributions, and creation dates. Extensive human activities have occurred in this region since at least in the late Tang Dynasty (618–907 ad). Although historical records show that most of the region’s rivers dried up around 1372, surface water persisted in some areas until the early Qing Dynasty (1644–1911 ad). After the 1600s, extensive nebkhas began to develop due to drying of the region’s rivers. The early stages of nebkha development were controlled by both the sediment supply and the regional wind regime, whereas late stages were controlled primarily by variations in wind activity. In the Alaxa Plateau, it took about 100 years for arable lands and riverbeds to evolve into gobi deserts, and during this time, several phases occurred with different levels of wind activity. The land degradation processes in this region are mainly controlled by surface water resources, and the impact of human activities such as reclamation on land degradation appear to have been overestimated in previous studies.     

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km~2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha~(-1) yr~(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha~(-1) yr~(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(5 t ha~(-1) yr~(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.     

A geospatial model for the optimization grazing management in semi-arid rangeland of Iran

Extensive livestock grazing even in unsuitable land has increasingly grown in most parts of semi-arid rangeland. Therefore, it is of paramount importance to identify suitable land for livestock grazing for optimum utilization while causing minimum impact to the environment. This paper adapted the schematic model based on the concepts presented by the Food and Agriculture Organization of suitability analysis for optimal grazing management in semi-arid rangeland in Iran. Factors affecting extensive grazing were determined and incorporated into the model. Semi-arid rangeland with variable such as climate and other agents were examined for common types of animal grazing and the advantages and limitations were elicited. Many ecosystem components affect land suitability for livestock grazing but due to time and funding restrictions, the most important and feasible elements were investigated. Within the model parameters, three submodels including water accessibility source, forage production, and erosion sensitivity were considered. Suitable areas at four levels of suitability were determined using geographic information systems. This suitability modeling approach was adopted due to its simplicity and the minimal time required for transforming and analyzing datasets. The most important reducing factors in model suitability were found to be: (a) land use and vegetation cover (in relation to soil erosion sensitivity), (b) the amount of the available forage in comparison with the total production, and (c) the existence of less palatability plants among the pasture plant species (forage production suitability). The results of the study would be beneficial to rangeland managers in devising measures more wisely to cope with the limitations and enhance the health and productivity of the rangelands.     

Local‐scale adaptations: A modeled assessment of soil,landscape, microclimatic,and management factors in Norse home‐field productivities

Adaptation of farming practices to inherent site conditions was essential to the success of Norse colonization in pristine landscapes. A key factor in the initial success of colonization, or landnám, of Iceland was management of the area adjacent to the domestic dwelling, the home‐field, to provide fodder for over‐wintering livestock. In this paper we examine three settlement home‐fields in the Mývatn and Laxá valley area of northeast Iceland. Contemporary evidence reveals a distinct climatic toposequence together with differences in the nature of the inherent soils between sites. By considering the influence of these differences, microscale adaptations in early land management practices in the production of hay are sought within a tightly defined chronological context. Using an integrated agroecosystem modeling approach, the factors affecting long‐term sustainability of hay production in the Norse home‐field are examined. Results indicate that regional‐level climate differences will have an impact on production, especially pronounced cold periods. It is also clear that small‐scale climate factors, as well as inherent soil differences between sites influenced productivity for the Norse farmer. However, productivities overall are at subsistence level, emphasizing the need for optimized land management to sustain home‐field production. After examining different management scenarios, it is apparent that the effect of an increased rate of manuring will be most apparent during the first century of settlement; thereafter the effect is relatively diminished. © 2008 Wiley Periodicals, Inc.     

A GIS model for settlement suitability regarding disaster mitigation, a case study in Bolu Turkey

A GIS (Geographic Information Systems) model was developed for Bolu Province in Turkey primarily for earthquake disaster mitigation purposes. The model served as the basis for investigating earthquake disaster vulnerability of existing settlements and identifying areas for new settlements in the Bolu Provincial Center and its counties. The set of criteria investigated in the GIS model was the following: distance from the main fault, ground acceleration, geologic basement type and terrain slope. Based on these criteria, a settlement suitability map was created, which classified the province into low, medium and high settlement suitable areas. This map was then augmented with other criteria for refinement purposes. These included the land use capability classes map of the province, the contemporary land use map derived from satellite images and the historical and contemporary earthquake occurrences within the region. Finally, the road network of the province derived from satellite images was overlaid on the settlement suitability map so that the provincial administrators could leave an evacuation zone of 200 m around the roads. This settlement suitability map is also intended to assist provincial administrators in making plans for reinforcement of existing settlements in low settlement suitable regions and opening new areas for urbanization and industrialization in high settlement suitable regions.     

Proposal for selection of control,preventive and rehabilitation measures based on degradation land level and geoindicators in the fortaleza metropolitan region,State of Ceará, Brazil

Preventive, controlling, rehabilitative and corrective measures to improve the environmental quality of the hydrographic basins of the Fortaleza metropolitan region in the state of Ceará (Brazil) are presented based on geological and geotechnical data, land degradation rates and sources, and other geoindicators. The region is affected by coastal and stream erosion, gravitational mass movement, dunes, silting, and water pollution, sanitary landfills in inappropriate sites, decommissioned and abandoned aggregate mining, and swamp areas. Geoindicators were used to classify each of the 12 hydrographic basins as possessing low (4), intermediate (3), or high (5) degradation levels. A group of 59 environmental management measures related to ecological, bioengineering, mechanical, policy and administrative, agricultural and clean-up methods was selected. From this general group a set of 31 measures was chosen considering goals, efficacy for specific environmental problems, suitability for large or small areas, behavior under different annual climatic conditions, environmental problems of the region, geological and geotechnical limitations and degradation level of the basins. A set of the more suitable geoindicators was selected for monitoring efficiency of the measures for each basin.     

RETRACTED ARTICLE: Assessment of soil erosion using RUSLE and GIS: a case study of the Maotiao River watershed,Guizhou Province,China

Due to the existence of fragile karst geo-ecological environments, such as environments with extremely poor soil cover, low soil-forming velocity, and fragmentized terrain and physiognomy, as well as inappropriate and intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of southwestern China; evaluation of soil loss and spatial distribution for conservation planning is urgently needed. This study integrated the revised universal soil loss equation (RUSLE) with a GIS to assess soil loss and identify risk erosion areas in the Maotiao River watershed of Guizhou. Current land use/cover and management practices were evaluated to determine their effects on average annual soil loss and future soil conservation practices were discussed. Data used to generate the RUSLE factors included a Landsat Thematic Mapper image (land cover), digitized topographic and soil maps, and precipitation data. The results of the study compare well with the other studies and local data, and provide useful information for decision makers and planners to take appropriate land management measures in the area. It thus indicates the RUSLE–GIS model is a useful tool for evaluating and mapping soil erosion quantitatively and spatially at a larger watershed scale in Guizhou.     

Vegetation change,erosion risk and land management on the Nullarbor Plain,Australia

 Arid karst landscapes that have been degraded by human activities provide a challenge for rehabilitation and an opportunity to test ideas about the stability and resilience of limestone ecosystems. The Nullarbor Plain is the largest arid karst area in Australia (220 000 km²) and is divided into extensive closed karstic depressions separated by low rocky ridges, while the dominant vegetation is chenopod shrubland. Since European settlement there has been considerable change in the vegetation, with significant reduction in shrub and grass cover over large areas of the plain. These changes are related to a state and transition model of vegetation dynamics which incorporates climatic variability, fire history and grazing pressure from sheep, kangaroos and rabbits. A partial sediment budget using ¹³⁷Cs inventories reveals local and regional patterns of soil redistribution within this arid karst landscape. Rehabilitation of eroded soil in pastoral lands has been accomplished at several sites but is labour intensive and vulnerable to climatic fluctuations. Given the low stock numbers, limited number of people involved, and poor economic returns, it would be sensible to make pastoral activities on the Nullarbor secondary to conservation priorities. This would necessitate a change in land ethic to stewardship, with emphasis on rehabilitation and control of feral animals. Management of increased numbers of visitors to the caves and karst also requires that resource inventories and management plans for each area be drawn up and used. Received: 1 June 1995 · Accepted: 4 December 1995     

Land conservation campaign in China: integrated management, local participation and food supply option

In an effort to halt soil erosion, desertification and sandstorms, the Chinese government has recently launched a series of land conservation programs targeted at the country’s north, northwest and southwest areas where problems are severe. This paper provides an overview of the current status of the major land conservation projects and their environmental and social-economic significance, as well as the challenges encountered. Conflicts of interests and objectives among different administrative entities involved and problems associated with the lack of local participation are addressed. Impacts on the food economy and implications for the environment are discussed in light of the options for meeting the country’s increasing food demand. The analysis highlights the necessity of improving cooperation and integration across different administrations and the imperative of participation of local communities in the planning and management process for achieving the goals of land conservation campaign. The importance of internalizing the environmental externality of land degradation and stipulating sustainable national food supply strategies is also stressed.     

Evidence against early nineteenth century major European induced environmental impacts by illegal settlers in the New England Tablelands,south eastern Australia

Paleoenvironmental reconstructions from Little Llangothlin Lagoon have been used to argue for early European impact on the eastern Australian landscape. In particular, these studies have argued for European arrival on the New England Tablelands at about 1800 AD, with significant impacts including the clearance of one species of Casuarina before 1820 AD and significant erosion by 1836 AD (Gale et al., 1995; Gale and Pisanu, 2001; Gale and Haworth, 2002, 2005). We have re-cored the lagoon, dated the cores using ²¹⁰Pb and radiocarbon, and counted pollen and other proxies. Our ²¹⁰Pb results indicate that ²¹⁰Pb background was achieved stratigraphically later than the erosion event and we have three early Holocene radiocarbon ages in the erosion event interval. We conclude that the ‘erosion event’ predates European settlement. The ²¹⁰Pb results indicate much less erosion in response to European settlement than suggested by these earlier studies. We also find no notable decline in Casuarina in the pollen record spanning the time of initial European impact, and in fact we find very little Casuarina in the record. Instead of a Casuarina dominated vegetation we conclude that the area was dominated by open Eucalypt forest prior to European settlement. Rather than changes in the regional vegetation in the early 19th century, we attribute changes in the palynoflora spanning the ‘erosion event’ to changes within the lake/wetland and in particular to changes in the dominance of different species of Myriophyllum; most likely due to water depth fluctuation. This site has stood out as indicating an earlier European impact than other localities in eastern Australia, beyond the original limits of settlement near Sydney. Our findings suggest that a more traditional interpretation of this site is warranted and that no very early impact is discernable.     

Assessing the geoindicators of land degradation in the Kashmir Himalayan region, India

The geoindicators of land degradation such as erosion, vegetation change and wetland loss were identified in the Kashmir Himalayan region using a geospatial model. Geomatics techniques were used to generate information on landuse/landcover, NDVI, slope and the lithological formations that form inputs to map the erosion risk. The results of erosion analysis revealed that 48.27?% of the area is under very high erosion risk. The Middle Himalayan watersheds were found to be under high erosion risk compared to the Greater Himalayan watersheds. Pohru and Doodhganga watersheds of the Middle Himalayas were found to be under very high erosion risk. These two watersheds were studied in detail from 1992 to 2001 for vegetation change and wetland loss. In Pohru watershed, significant change was found in the dense forest with 10?% decrease. Wular lake, an important wetland in the Pohru watershed, has shrunk by 2.7?km² during the last decade. The vegetation change analysis of the Doodhganga watershed revealed that there has been 9.13?% decrease in the forest, 7?% increase in built up and the largest wetland in the Doodhganga, Hokarsar, has reduced by 1.98?km² from 1992 to 2001. Field studies showed that anthropogenic activities and chemically deficit soil (Karewa) along Pir Panjal ranges are the main factors responsible for high land degradation in the area. The assessment of these geoindicators provided valuable information for identifying causes and consequences of the land degradation and thus outlining potential hazard areas and designing remedial measures.     

Land cover change over the last three centuries due to human activities: The availability of new global data sets

Land use and land cover change is an important driver of global change (Turner et al., 1993). It is recognized that land use change has important consequences for global and regional climates, the global biogeochemical cycles such as carbon, nitrogen, and water, biodiversity, etc. Nevertheless, there have been relatively few comprehensive studies of global, long-term historical changes in land cover due to land use. In this paper, we review the development of global scale data sets of land use and land cover change. Furthermore, we assess the differences between two recently developed global data sets of historical land cover change due to land use. Based on historical statistical inventories (e.g. census data, tax records, land surveys, historical geography estimates, etc) and applying different spatial analysis techniques, changes in agricultural land cover (croplands, pastures) were reconstructed for the last 300 years. The two data sets indicate that cropland areas expanded from 3–4 million km² in 1700 to 15–18 million km² in 1990 (mostly at the expense of forests), while grazing land area expanded from 5 million km² in 1700 to 31 million km² in 1990 (mostly at the expense of natural grasslands). The data sets disagree most over Latin America and Oceania, and agree best over North America. Major differences in the two data sets can be explained by the use of a fractional versus Boolean approach, different modelling assumptions, and inventory data sets.     

Impacts and Timing of the First Human Settlement on Vegetation of the Faroe Islands

Stratigraphically precise AMS-radiocarbon-dated plant remains, pollen, charcoal, and microtephra analyses from the Faroe Islands were used to establish the timing and effects of the first human settlement. The first occurrence of cultivated crops from three locations dated from as early as the sixth century A.D. and was older than implied from previous archaeological and historical studies, but consistent with earlier palaeoecological investigations. The effects of settlement on the vegetation were rapid and widespread. The transformation of the flora of this fragile ecosystem was best expressed by the large assemblage of ruderal, postsettlement plants recorded as macrofossils. The earliest known introduction of domestic animals (sheep/goat) was ca. A.D. 700. Their arrival on these relatively small islands probably contributed to the widespread change in vegetation and the loss of restricted native woody cover. Settlement was the critical disturbance that transformed an ecosystem that was already stressed by climatic change, as sensed by regional marine sediments. The settlement dates conform to a pattern of older dates developing from throughout the north Atlantic region.