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1.
Tropical deforestation is widely believed to directly influence the climate at a number of scales. Yet while much has been written about the tropical forest-climate relationship, there is little empirical evidence showing if and how local and regional climates are modified by deforestation. This study presents the results of an analysis of deforestation and climate change in a rain forest in southern Mexico. Records from 18 climate stations in the Selva Lacandona of Chiapas, Mexico were examined and related to an analysis of deforestation based on Landsat images. The area surrounding some stations has been deforested since the stations were established, while the area surroundings others has remained forested. Strong climatic trends were generally evident at the deforested stations, including decreases in the average daily maximum temperature and temperature range. No precipitation changes were observed. A comparison of the results with microclimatic experiments and modeling studies suggests that the climatic impacts of deforestation are overgeneralized at the local scale. Landscape heterogeneity appears to influence the biophysical mechanisms linking tropical forests and climate, and should be explicitly represented in modeling studies.  相似文献   

2.
Although tropical deforestation bears a close relationship with climate change, its exact contribution to climate warming and its threshold of exerting a noticeable influence remain unknown. This study attempts to bridge this knowledge gap by analyzing deforestation data of Heilongjiang Province, China in relation to climate data. It is found that forest cover was reduced from 238,335 km2 in 1958 to 216,009 km2 in 1980, and further to 207,629 km2 in 2000. During this period the provincial annual temperature rose by 1.68 °C, against the nation-wide warming of 0.99 °C during the same period. At the provincial level the observed deforestation caused a warming in the vicinity of 0.69 °C. This warming does not bear any definite relationship with latitude and elevation. At the local scale, deforestation is related inversely to the rise in decadal temperature in the form of ΔT = −0.013ΔF + 0.4114 (R2 = 0.30). There is a positive relationship between the accuracy (R2 value) of predicting climate warming from deforestation and its severity. The critical threshold for deforestation to exert a noticeable impact on climate warming (e.g., R2 = 50%) appears to be 5 km2. The amount of forest cover at the beginning of a period can inhibit temperature rise, but its exact effect on climate warming is difficult to quantify.  相似文献   

3.
State-of-the-art impact-modeling studies in environmental and climatological sciences require detailed future deforestation scenarios that allow forest to be replaced by a mosaic of multiple successional land-cover types, rather than the simple conversion of forest to a single land-cover type, such as bare soil or cropland. Therefore, not only the amount and location of forest removal has to be known (as is typically provided by scenarios), but also knowledge about the successional land-cover types and their relative areal proportions is needed. The main objective of this study was to identify these successional land-cover types and quantify their areal proportions in regions deforested during the past 37 years around the city of Kisangani, D.R. Congo. The fallow vegetation continuum was categorized in different stages, adapted from existing classifications. Ground-truth points describing the present-day vegetation were obtained during a field campaign and used for supervised and validated land-cover classification of these categories, using the Landsat image of 2012. Areal proportions of successional land-cover types were then derived from the resulting land-cover map. The second objective of this study was to relate these areal proportions to time since deforestation, which is expected to influence fallow landscapes. Landsat images of 1975, 1990, and 2001 were analyzed. Present-day mature tree fallow is less abundant on areas deforested during 1975–1990. The relative areal proportions were used to refine a deforestation scenario and apply it to existing data-sets of LAI and canopy height (CH). Assuming a simple conversion of forest to cropland, the deforestation scenario projected a reduction of grid-cell-averaged CH from 25.5 to 7.5 m (within deforested cells), whereas the refined scenarios that we propose show more subtle changes, with a reduced CH of 13 m. This illustrates the importance of taking successional land cover correctly into account in environmental and climatological modeling studies.  相似文献   

4.
This study evaluates the dynamics and identifies the indirect biophysical and socio‐economic factors related to the recovery, degradation and deforestation of the tropical dry forest (TDF) cover in the municipality of Tehuantepec, Oaxaca, Mexico. Annual rates and transition matrices were determined to identify indirect factors; the cartographic information of 25 variables with shift points were overlaid and Generalized Linear Models (GLM) were applied. The change process with the greatest impact in TDF during the study period (1993–2011) was degradation, with 10468 ha degraded (12 per cent of the initial tropical cover); recovery of coverage was the second most important change process, with 4808 ha (5.5 per cent); and deforestation was the change process with the lowest impact, with a loss of 2800 ha (3.23 per cent). The net balance was negative, with a decrease (through land degradation and deforestation) of 8460 ha (9.75 per cent). The recovery of coverage was mainly associated with biophysical factors such as land suitability and accessibility to natural vegetation. On the other hand, deforestation and degradation of coverage were associated with both biophysical and socioeconomic factors such as land suitability, accessibility to natural vegetation, migration, marginalization, population pressure, economy, education and health. The findings of this study determined the spatial distribution of forest recovery, deforestation and degradation processes at a regional level, allowing for future researchers to focus their efforts at local and landscape levels. Also, the work allows for an approximation of the factors associated with the change processes studied, hence supporting the allocation of resources for the establishment of management, conservation, development and restoration strategies of tropical dry forests at the regional level.  相似文献   

5.
The objective of study was to explore short-term trends of processes that determine land-use change in Sierra Norte of Oaxaca (SNO), Mexico. Land use and land cover changes (LULCC) were estimated in a complex mosaic of vegetation in the SNO from 1980 to 2000, and projected them to 2020 through a Markovian model. SNO is highly vulnerable to climatic change according to a 2050 GCM scenario. However, 3% annual rate of tropical and temperate forest deforestation from agriculture and livestock encroachment, suggest the threat from land-use change is higher than that from climatic change for this study site. Productive land-use strategies are needed to reduce such high deforestation rates for tropical regions. Controlling deforestation would also reduce short-term effects of CO2 emissions to the atmosphere. Because of the necessity to evaluate anthropogenic ecosystem changes, it is imperative to separate short-term influences such as deforestation, from long-term influences such as climatic change.  相似文献   

6.
Paleorecords from multiple indicators of environmental change provide evidence for the interactions between climate, human alteration of watersheds and lake ecosystem processes at Lake Tanganyika, Africa, a lake renowned for its extraordinary biodiversity, endemism and fisheries. This paper synthesizes geochronology, sedimentology, paleoecology, geochemistry and hydrology studies comparing the history of deltaic deposits from watersheds of various sizes and deforestation disturbance levels along the eastern coast of the lake in Tanzania and Burundi. Intersite differences are related to climate change, differences in the histories of forested vs. deforested watersheds, differences related to regional patterns of deforestation, and differences related to interactions of deforestation and climate effects. Climate change is linked to variations in sediment accumulation rates, charcoal accumulation, lake level and water chemistry, especially during the arid-humid fluctuations of the latter part of the Little Ice Age. Differences between forested and deforested watersheds are manifested by major increases in sediment accumulation rates in the latter (outside the range of climatically driven variability and for the last 40 years unprecedented in comparison with other records from the lake in the late Holocene), differences in eroded sediment and watershed stream composition, and compositional or diversity trends in lake faunal communities related to sediment inundation. Variability in regional patterns of deforestation is illustrated by the timing of transitions from numerous sedimentologic, paleoecologic and geochemical indicators. These data suggest that extensive watershed deforestation occurred as early as the late-18th to the early-19th centuries in the northern part of the Lake Tanganyika catchment, in the late-19th to early-20th centuries in the northern parts of modern-day Tanzania, and in the mid-20th century in central Tanzania. Rapid increases in sediment and charcoal accumulation rates, palynological and lake faunal changes occurred in the early-1960s. We interpret this to be the result of greatly enhanced flushing of sediments in previously deforested watersheds triggered by extraordinary rainfall in 1961/62. Regional differences in deforestation histories can be understood in light of the very different cultural and demographic histories of the northern and central parts of the lake shoreline. Incursion of slaving and ivory caravans from the Indian Ocean to the central coast of Lake Tanganyika by the early-19th century, with their attendant diseases, reduced human and elephant populations and therefore maintained forest cover in this region through the late-19th to early-20th centuries. In contrast, the northeastern portion of the lakeshore did not experience the effects of the caravan trades and consequently experienced high human population densities and widespread deforestation much earlier. These studies demonstrate the importance of paleolimnological data for making informed risk assessments of the potential effects of watershed deforestation on long-term lake ecosystem response in the Lake Tanganyika catchment. Differences in sediment yield and lake floor distribution of that yield, linked to factors such as watershed size, slope, and sediment retention, must be accounted for in management plans for both human occupation of currently forested watersheds and the development of future underwater reserves.  相似文献   

7.
In spite of widely documented studies of deforestation rates and land use/cover changes in tropical dry forests in Mexico, relatively little is known about fragmentation patterns in such forests. This study defines the spatial distribution of landforms and land use/cover types the lower Papagayo River basin and examines their influence on fragmentation patterns and biological diversity in a tropical dry forest in that southern Pacific region. The land use/cover map was constructed from aerial photographs, Landsat TM imagery (2000) and fieldwork. Landform units were defined based on altitude, slope, lithology and morphology. Landscape fragmentation parameters were obtained using FRAGSTATS (version 3.3) considering the numbers of patches, mean, minimum and maximum patch size, edge density, total edge and connectivity. Results show tropical dry forest to be remnant vegetation (~11 per cent), characterized by isolation and low connectivity. Land use/cover types have different effects on fragmentation patterns. Agriculture and cattle raising produce similar numbers of patches, but with a different mean size; and human settlements have a scattered distribution pattern. The abandonment of rural agricultural livelihoods has favoured the expansion of secondary tropical dry forest characterized by continuity and high connectivity, which suggests a high regeneration potential from land abandonment. It can be concluded that tropical dry forest fragmentation and recovery at regional scales depend on such landscape attributes as lithology, slope, geomorphology and management.  相似文献   

8.
Tropical forests play a major role in storing large carbon stocks and regulating energy, and water fluxes, but such forest cover is decreasing rapidly in spite of the policy attention on reducing deforestation. High-resolution spatiotemporal maps are unavailable for the forests in majority of the tropical regions in Asia because of the persistent cloud cover and haze cover. Recent advances in radar remote sensing have provided weather-independent data of earth surface, thus offering an opportunity to monitor tropical forest change processes with relatively high spatiotemporal resolutions. In this research, we aim to examine the tropical deforestation process and develop a spatial model to simulate future forest patterns under various scenarios. Riau Province from central Sumatra of Indonesia is selected as the study area; this province has received much attention worldwide because the highest CO2 emission resulting from tropical deforestation has been recorded. Annual time series PALSAR data from 2007 to 2010 were analyzed for forest mapping and detecting land cover changes. A spatial model was calibrated using the Bayesian method. Modeling parameters were customized for the local subregions that allocate deforestation on the basis of their empirical relationships to physical and socioeconomic drivers. The model generated landscape spatial patterns mirrored the possible locations and extent of deforested areas by 2030 and provided time-series crucial information on forest landscape under various scenarios for future landscape management projects. The results suggested that the current deforestation process is in a critical stage where some subregions may face unprecedented stress on primary forest costing rivers and forest ecosystems by the end of 2020. The perspective views of Riau Province generated by the model highlighted the need for forest/environmental planning controls for the conservation of environmentally sensitive areas.  相似文献   

9.
Tropical forests have been recognized as having global conservation importance. However,they are being rapidly destroyed in many regions of the world. Regular monitoring of forests is necessary for an adaptive management approach and the successful implementation of ecosystem management. The present study analyses the temporal changes in forest ecosystem structure in tribal dominated Malkangiri district of Orissa,India,during 1973-2004 period based on digitized forest cover maps using geographic information system (GIS) and interpretation of satellite data. Three satellite images Landsat MSS (1973),Landsat TM (1990) and IRS P6 LISS III (2004) were used to determine changes. Six land cover types were delineated which includes dense forest,open forest,scrub land,agriculture,barren land and water body. Different forest types were also demarcated within forest class for better understanding the degradation pattern in each forest types. The results showed that there was a net decrease of 475.7 km2 forest cover (rate of deforestation = 2.34) from 1973 to 1990 and 402.3 km2 (rate of deforestation = 2.27) from 1990 to 2004. Forest cover has changed over time depending on a few factors such as large-scale deforestation,shifting cultivation,dam and road construction,unregulated management actions,and social pressure. A significant increase of 1222.8 km2 agriculture area (1973-2004) clearly indicated the conversion of forest cover to agricultural land. These alterations had resulted in significant environmental consequences,including decline in forest cover,soil erosion,and loss of biodiversity. There is an urgent need for rational management of the remaining forest for it to be able to survive beyond next decades. Particular attention must be paid to tropical forests,which are rapidly being deforested.  相似文献   

10.
This work describes the temperature trends of the Nuuk fjord area during the last century and analyses the spatial variability of temperature and precipitation along the coast‐inland gradient of the region. A better understanding of the climate of the coastal region of Greenland is important for ice sheet studies since significant thinning has recently been detected on local outlet glaciers with driving factors still to be identified. The glaciological reconstruction of the ice sheet mass balance has often made use of climate datasets from the coastal stations to substitute missing data from the inland areas. The information on the coast‐inland gradient of temperature and precipitation hereafter provided is of relevance in other areas around the ice sheet as it represents a mean for increasing the accuracy of historical glacier‐climate interactions. We therefore discuss climatological information from the automatic station that operated at the glacier throughout the 1980s as well as from other stations located along the fjord and with a longer coverage.  相似文献   

11.
The detection of vegetation fires using remote sensing has proven useful for highlighting areas undergoing rapid conversion in humid forests, but not in tropical dry forest (TDF). To further understand this relationship, we explored the correlation between MODIS Active Fires and forest cover change at local scales using 3 × 3 km sampling grids in three TDF landscapes in Bolivia; Mexico, and Brazil. Our analysis showed no single overall correlation among sites between the frequency of fires reported by the MODIS Active Fire Mapping product and forest cover change. Also, aggregated patterns of fire occurrence in Brazil and Bolivia did not correspond to areas with high percentage of forest loss, which indicates that the fire/deforestation relationship in TDF is not apparent in a simple fire frequency map. However, statistically significant correlations were found in sampling boxes with 50–60%, 50–70%, 50–95% forest cover at “initial state” of the time series in the Mexican site, Bolivian site and Brazilian site, respectively. Our findings suggest that complex interactions between anthropogenic fire-use, satellite-detected fires, and deforestation in highly fragmented TDF landscapes are difficult to describe at regional scales and might only be possible to analyze using finer resolution sampling grids.  相似文献   

12.
1956-2003年拉萨河流域径流变化趋势   总被引：4，自引：1，他引：3  
Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows： （1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season.  相似文献   

13.
Tropical forests have been recognized as having global conservation importance. However, they are being rapidly destroyed in many regions of the world. Regular monitoring of forests is necessary for an adaptive management approach and the successful implementation of ecosystem management. The present study analyses the temporal changes in forest ecosystem structure in tribal dominated Malkangiri district of Orissa, India, during 1973–2004 period based on digitized forest cover maps using geographic information system (GIS) and interpretation of satellite data. Three satellite images Landsat MSS (1973), Landsat TM (1990) and IRS P6 LISS III (2004) were used to determine changes. Six land cover types were delineated which includes dense forest, open forest, scrub land, agriculture, barren land and water body. Different forest types were also demarcated within forest class for better understanding the degradation pattern in each forest types. The results showed that there was a net decrease of 475.7 km2 forest cover (rate of deforestation = 2.34) from 1973 to 1990 and 402.3 km2 (rate of deforestation = 2.27) from 1990 to 2004. Forest cover has changed over time depending on a few factors such as large-scale deforestation, shifting cultivation, dam and road construction, unregulated management actions, and social pressure. A significant increase of 1222.8 km2 agriculture area (1973–2004) clearly indicated the conversion of forest cover to agricultural land. These alterations had resulted in significant environmental consequences, including decline in forest cover, soil erosion, and loss of biodiversity. There is an urgent need for rational management of the remaining forest for it to be able to survive beyond next decades. Particular attention must be paid to tropical forests, which are rapidly being deforested.  相似文献   

14.
In the 10,000 km2 San Pedro River watershed area in south-eastern Arizona, high-resolution spatial patterns of long-term precipitation and temperature were better reproduced by kriging climate data with elevation as external drift (KED) than by multiple linear regression on station location and elevation as judged by the spatial distribution of interpolation error. Mean errors were similar overall, and interpolation accuracy for both methods increased with increasing correlation between climate variables and elevation. Uncertainty in station locations had negligible effect on mean estimation error, although error for individual stations varied as much as 27%. Our future ability to examine spatial aspects of climate change at high spatial resolution will be severely limited by continuing closures of climate stations in this part of the United States.  相似文献   

15.
基于遥感和GIS的中国20世纪90年代毁林开荒状况分析   总被引：10，自引：0，他引：10  
毁林开荒过程是一种林地变为耕地的土地利用变化过程,可以通过遥感和GIS技术对这一过程进行监测。本文通过覆盖全国的TM影像数据,对20世纪90年代林地转为耕地的面积及其空间分布进行分析,从而对全国毁林开荒过程进行遥感监测。结果表明,该时期有17630km2的林地被开垦为耕地。不同面积等级的开垦过程在不同流域分布也不同:面积小于10hm2和介于10～100hm2的被开垦林地较广泛地分布于各大流域;而面积介于100～1000hm2的被开垦林地主要分布于松辽流域、黑龙江流域和东北东部流域、长江流域、珠江流域和云南省所在流域;大于1000hm2的被开垦林地则几乎全部分布于松辽流域、黑龙江流域和东北东部流域。坡度大于3°的毁林开荒地面积占总面积的295%;对土壤侵蚀背景的分析表明,土壤侵蚀强度以微度和轻度为主  相似文献   

16.
Remote sensing technologies are increasingly used to monitor landscape change in many parts of the world. While the availability of extensive and timely imagery from various satellite sensors can aid in identifying the rates and patterns of deforestation, modelling techniques can evaluate the socioeconomic and biophysical forces driving deforestation processes. This paper briefly reviews some emerging spatial methodologies aimed at identifying driving forces of land use change and applies one such methodology to understand deforestation in Mexico. Satellite image classification, change analysis and econometric modelling are used to identify the rates, hotspots and drivers of deforestation in a case study of the southern Yucatán peninsular region, an enumerated global hotspot of biodiversity and tropical deforestation. In particular, the relative roles of biophysical and socioeconomic factors in driving regional deforestation rates are evaluated. Such methodological approaches can be applied to other regions of the forested tropics and contribute insights to conservation planning and policy.  相似文献   

17.
大型人工湖气候效应观测研究——以密云水库为例   总被引：2，自引：1，他引：1  
郑祚芳  任国玉  王耀庭  窦军霞 《地理科学》2017,37(12):1933-1941
应用近5 a自动气象站观测资料,分析了华北地区最大人工湖——密云水库的局地气候效应。结果表明：① 密云水库库区相比于附近平原地带具有气温偏低、湿度偏高、风速偏弱、降水量偏大等特点。水库对区域气候的影响范围约在10 km内,离水库越近的地方,受影响越大。② 密云水库的气候效应主要体现在夏半年,尤以气温和降水最为明显。③ 水库南、北两侧受到的局地环流的影响具有明显的差异,库区东西方向的年平均局地风速约为0.14 m/s,南北方向约为 0.10 m/s。下垫面属性的热力差异及特殊地形条件使得密云水库附近同时存在山谷风和湖陆风现象,其叠加效应是导致区域内不同位置间气象要素出现季节性及日变化差异的主要原因。  相似文献   

18.
Climate change is a global phenomenon but is modified by regional and local environmental conditions. Moreover, climate change exhibits remarkable cyclical oscillations and disturbances, which often mask and distort the long-term trends of climate change we would like to identify. Inspired by recent advancements in data mining, we experimented with empirical mode decomposition (EMD) technique to extract long-term change trends from climate data. We applied GIS elevation model to construct 3D EMD trend surface to visualize spatial variations of climate change over regions and biomes. We then computed various time-series similarity measures and plot them to examine spatial patterns across meteorological stations. We conducted a case study in Inner Mongolia based on daily records of precipitation and temperature at 45 meteorological stations from 1959 to 2010. The EMD curves effectively illustrated the long-term trends of climate change. The EMD 3D surfaces revealed regional variations of climate change, while the EMD similarity plots disclosed cross-station deviations. In brief, the change trends of temperature were significantly different from those of precipitation. Noticeable regional patterns and local disturbances of the changes in both temperature and precipitation were identified. The trends of change were modified by regional and local topographies and land covers.  相似文献   

19.
Climate change is a global phenomenon but is modified by regional and local environmental conditions.Moreover,climate change exhibits remarkable cyclical oscillations and disturbances,which often mask and distort the long-term trends of climate change we would like to identify.Inspired by recent advancements in data mining,we experimented with empirical mode decomposition(EMD) technique to extract long-term change trends from climate data.We applied GIS elevation model to construct 3 D EMD trend surface to visualize spatial variations of climate change over regions and biomes.We then computed various time-series similarity measures and plot them to examine spatial patterns across meteorological stations.We conducted a case study in Inner Mongolia based on daily records of precipitation and temperature at 45 meteorological stations from 1959 to 2010.The EMD curves effectively illustrated the long-term trends of climate change.The EMD 3 D surfaces revealed regional variations of climate change,while the EMD similarity plots disclosed cross-station deviations.In brief,the change trends of temperature were significantly different from those of precipitation.Noticeable regional patterns and local disturbances of the changes in both temperature and precipitation were identified.The trends of change were modified by regional and local topographies and land covers.  相似文献   

20.
提取1960-2005年西藏自治区粮食单产数据,选取4个典型气象台站,以粮食耕作面积作为加权因子获取综合气象因子数据,采用小波分析方法分析粮食产量对气候变化的响应关系,并预测后期西藏自治区粮食产量的总体趋势。研究发现,西藏粮食单产、气温、光照、降水均具有明显的25 a特征时间尺度的周期性波动,粮食产量对气候变化响应密切,气温偏暖、光照偏长、降水偏多对粮食生产较为有利。趋势预测表明西藏自治区的粮食生产正由相对丰年向相对贫年转化,需引起重视。  相似文献   

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