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1.
Mangrove forests provide vital ecosystem services for millions of people living in coastal communities. The expansion of aquaculture production and urbanization have been identified as major causes of mangrove clearance in South-East Asia. The Ca Mau peninsula in Vietnam is leading the country in shrimp aquaculture and at the same time, the region is home to the largest remaining mangrove forests. This study aims to assess the spatial and temporal mangrove forest dynamics in Ngoc Hien district in Ca Mau. Land cover change and fragmentation are quantified using remote sensing imagery consisting of a series of SPOT5 scenes from 2004, 2009 and 2013. The results indicate a high turnover of land cover change, with close to half of the mangrove forests being affected by land cover changes between 2004 and 2014. Net changes in mangrove forest are found to average −0.34% annually, characterized by deforestation between 2004 and 2009 and afforestation of between 2009 and 2013. Fragmentation remains a plausible threat; approximately 35.4% of the mangrove forests in Ngoc Hien are part of interior ‘core’ forests. Forest zones with different regulation regimes play a significant role in shaping the geographic distribution of mangrove forest changes. The insights into recent mangrove forest dynamics facilitate the informed discussion on improving future protection of the mangrove forests abiding anthropogenic pressures. 相似文献
2.
热带森林覆被的时空动态评价——以印度Malkangiri district of Orissa为例 总被引：1，自引：1，他引：0
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
3.
Ramon Felipe Bicudo da Silva Mateus Batistella Emilio Federico Moran Dengsheng Lu 《The Professional geographer》2017,69(1):80-93
The Atlantic Forest biome has only 13 percent of its pristine vegetation cover left. This article analyzes the consequences of land changes on forest cover in the Paraíba Valley, São Paulo state, Brazil, from 1985 to 2011. Multitemporal satellite image classifications were carried out to map eight land use and land cover classes. The forest cover increased from 2,696 km2 in 1985 to 4,704 km2 in 2011, mostly over areas of degraded pastures. The highest rates of afforestation were observed within protected areas around eucalyptus plantations. On the other hand, deforestation processes were concentrated on areas covered by secondary forests. Socioeconomic changes taking place in particular Brazilian settings, such as industrialization and agricultural modernization, allied to the Paraíba Valley's natural biophysical constraints for agricultural production, have led the region to experience a remarkable case of forest transition. 相似文献
4.
José Reyes Díaz‐Gallegos Jean‐François Mas Alejandro Velázquez 《Singapore journal of tropical geography》2010,31(2):180-196
We assessed deforestation in Southeast Mexico (a surface area of 29 000 km2 in seven states) through the comparison of land use/land cover maps at a scale of 1:250 000. This facilitated mapping of the land use/land cover change (LULCC) processes and calculation of the rates of change and the change matrix for the period 1978–2000. An original method was used to assess the accuracy of the LULCC map. The verification sites were selected through a stratified random sampling and were corroborated with aerial photographs for 1978 and 2000. Error matrices were elaborated using both hard and fuzzy set approaches in order to take into account the errors related to generalization of the map in fragmented landscapes. The results showed an average annual deforestation rate of 1.1 per cent which represents an average annual loss of 190 000 ha of forest, or an estimated total reduction of 4.2 million ha over 22 years. Furthermore, deforestation processes are concentrated in some areas such as Yucatan and Chiapas states, which registered major forest conversions to grassland and slash‐burning. The overall accuracy of the LULCC map, assessed with hard and fuzzy set approaches, was 72 per cent and 88 per cent respectively. 相似文献
5.
珠江口红树林湿地演变与现状的遥感分析 总被引：1，自引：0，他引：1
1 Introduction Half of the mangrove wetlands in China are situated in Guangdong province (Wang and Chen, 1998). The province used to have various types of wild mangrove forests along its coastal areas. The rapid expansion of urban areas and the fast deve… 相似文献
6.
The planned construction of hundreds of hydroelectric dams in the Amazon basin has the potential to provide invaluable ‘clean’ energy resources for aiding in securing future regional energy needs and continued economic growth. These mega-structures, however, directly and indirectly interfere with natural ecosystem dynamics, and can cause noticeable tree loss. To improve our understanding of how hydroelectric dams affect the surrounding spatiotemporal patterns of forest disturbances, this case study integrated remote sensing spectral mixture analysis, GIS proximity analysis and statistical hypothesis testing to extract and evaluate spatially-explicit patterns of deforestation (clearing of entire forest patch) and forest degradation (reduced tree density) in the 80,000 km2 neighborhoods of the Brazil's Tucuruí Dam, the first large-scale hydroelectric project in the Amazon region, over a period of 25 years from 1988 to 2013. Results show that the average rates of deforestation were consistent during the first three time periods 1988–1995 (620 km2 per year), 1995–2001 (591 km2 per year), and 2001–2008 (660 km2 per year). However, such rate dramatically fell to half of historical levels after 2008, possibly reflecting the 2008 global economic crisis and enforcement of the Brazilian Law of Environmental Crimes. The rate of forest degradation was relatively stable from 1988 to 2013 and, on average, was 17.8% of the rate of deforestation. Deforestation and forest degradation were found to follow similar spatial patterns across the dam neighborhoods, upstream reaches or downstream reaches at the distances of 5 km–80 km, suggesting that small and large-scale forest disturbances may have been influencing each other in the vicinity of the dam. We further found that the neighborhoods of the Tucuruí Dam and the upstream region experienced similar degrees of canopy loss. Such loss was mainly attributed to the fast expansion of the Tucuruí town, and the intensive logging activities alongside major roads in the upstream reservoir region. In contrast, a significantly lower level of forest disturbance was discovered in the downstream region. 相似文献
7.
Mangrove forests have important ecological functions in protecting the environment. However, the mangrove wetlands have been largely lost because of intensified human activities in the study area. Remote sensing can be conveniently used for the inventory of mangrove forests because field investigation is very difficult. In this study, a knowledge-based system is developed to retrieve spatio-temporal dynamics of mangrove wetlands using multi-temporal remote sensing data. Radar remote sensing data are also used to provide complementary information for the quantitative analysis of mangrove wetlands. Radar remote sensing is able to penetrate mangrove forests and obtain the trunk information about mangrove structures. The integration of radar remote sensing with optical remote sensing can significantly improve the accuracies of classifying mangrove wetland types and estimating wetland biomass. 相似文献
8.
9.
Francisco Guerra‐Martínez Arturo García‐Romero Andrea Cruz‐Mendoza Laura Osorio‐Olvera 《Singapore journal of tropical geography》2019,40(3):387-409
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
10.
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
11.
利用1976—2021年共6期遥感影像获取了海口市东寨港红树林自然保护区范围内不同年代的湿地数据,基于转移矩阵、问卷调查和主成分分析,剖析了45年来保护区红树林的变化及其与周边社区的关系。结果显示：1)保护区内红树林面积由1976年的1 395.84 hm2增至2021年的1 589.28 hm2,期间呈“骤减缓升”之势。除1976—1985年红树林面积有减少外(减少了250 hm2,减少幅度为18%),其余时段红树林面积均为增长态势。2) 1976—2021年保护区红树林转出对象分别是淤泥质海滩(34.32 hm2)、河流(25.81 hm2)、海水养殖场(21.06 hm2)、其他用地(10.58 hm2)和洪泛湿地/内陆滩涂(8.26 hm2);转入为红树林的对象主要是淤泥质海滩(177.41 hm2)、河流(38.18 hm2)、其他用地(28.21 hm 相似文献
12.
我国湿地的主要生态问题及治理对策 总被引：11，自引：0，他引：11
在参阅相关文献和实地调查的基础上,分析了我国湿地面临的主要生态问题,将湿地生态系统结构与功能的退化划分为缺水萎缩、污染退化、泥沙淤积退化、疏干排水退化、生物资源过度利用与生物多样性受损、红树林破坏、生物入侵退化等7个类型。在此基础上,提出湿地生态保育与治理的若干对策。 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.
Over the past few decades, land use and land cover change has become a global concern. In the Lop Buri province of Thailand, rapid land cover change, specifically conversion of forests to agriculture, has occurred. The purpose of the study is to identify the predictors of land cover change in Lop Buri province for land that has been converted to upland crops or has undergone deforestation between 1989 and 2006. Four logistic regression models were constructed using spatially explicit biophysical and geo‐social data, to account for changes to upland crops and forest loss from1989–98 and 1998–2006. Across the four models, slope, distance to forest edge, distance to towns, distance to roads, population size, and population density in various stand‐alone and interactive forms were found to be the most consistent predictors of land cover change. 相似文献
15.
Cristian Echeverría Adrian NewtonLaura Nahuelhual David CoomesJosé María Rey-Benayas 《Applied geography (Sevenoaks, England)》2012,32(2):822-831
A comprehensive understanding of the patterns that occur as human processes transform landscapes is necessary for sustainable development. We provide new evidence on how landscapes change by analysing the spatial patterns of human processes in three forest landscapes in southern Chile at different states of alteration (40%-90% of old-growth forest loss). Three phases of landscape alteration are distinguished. In Phase I (40%-65% of old-growth forest loss), deforestation rates are < 1% yr−1, forests are increasingly degraded, and clearance for pastureland is concentrated on deeper soils. In Phase II (65%-80%), deforestation reaches its maximum rate of 1-1.5% yr−1, with clearance for pastureland being the main human process, creating a landscape dominated by disturbed forest and shrubland. In this phase, clearance for pastureland is the primary driver of change, with pastures expanding onto poorer soils in more spatially aggregated patterns. In Phase III (80%-90%), deforestation rates are again relatively low (<1% yr−1) and forest regrowth is observed on marginal lands. During this phase, clearance is the dominant process and pastureland is the main land cover. As a forest landscape is transformed, the extent and intensity of human processes vary according to the existing state of landscape alteration, resulting in distinctive landscape patterns in each phase. A relationship between spatial patterns of land cover and human-related processes has been identified along the gradient of landscape alteration. This integrative framework can potentially provide insights into the patterns and processes of dynamic landscapes in other areas subjected to intensifying human use. 相似文献
16.
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
17.
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
18.
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
19.
JAMES S. GARDNER 《Geographical review》2002,92(2):282-306
ABSTRACT. Hazardous processes, including floods, landslides, soil erosion, and debris flows, are common in the Himalaya. Deforestation has been held responsible for increasing risk from such hazards in the Indian context for more than a century. The deforestation‐hazard linkage in the Kullu District of Himachal Pradesh is examined. Evidence suggests that the extent of forest cover has altered little over 150 years and that hazardous processes recur in much the same locations, with similar frequency and magnitude, except where road construction has increased slope instability. Nonetheless, population growth and economic development, especially since 1990, have increased vulnerability to hazards. 相似文献
20.
ABSTRACT. Tropical montane forests are known for their ecological importance. Most montane forests in Ecuador have been converted to agriculture, and those that remain are concentrated on the eastern cordillera. Understanding of land‐use‐land‐cover change in this ecological zone is inadequate. Using remote sensing (Landsat tm, spot ) and fieldwork, we document land‐use‐land‐cover change in two watersheds on Ecuador's eastern cordillera (Cañar Province). During the 1990s the region experienced a 0.58 percent annual rate of deforestation, but two areas within it show active signs of re/afforestation. Although conversion of forest to pasture for cattle grazing continues, human migration to the United States is likely to affect the trajectory of future land‐use‐land‐cover change. 相似文献