Mangrove conversion and aquaculture development in Vietnam: A remote sensing-based approach for evaluating the Ramsar Convention on Wetlands

Remote sensing data have been proposed as a potential tool for monitoring environmental treaties. However, to date, satellite images have been used primarily for visualization, but not for systematic monitoring of treaty compliance. In this paper, we present a methodology to operationalize the use of satellite imagery to assess the impact of the Ramsar Convention on Wetlands. The approach uses time series analysis of landscape pattern metrics to assess land cover conditions before and after designation of Ramsar status to monitor compliance with the Convention. We apply the methodology to two case studies in Vietnam and evaluate the success of Ramsar using four metrics: (1) total mangrove extent; (2) mangrove fragmentation; (3) mangrove density; and (4) aquaculture extent. Results indicate that the Ramsar Convention did not slow the development of aquaculture in the region, but total mangrove extent has remained relatively constant, primarily due to replanting efforts. Yet despite these restoration efforts, the mangroves have become fragmented and survival rates for replanting efforts are low. The methodology is cost effective and especially useful to evaluate Ramsar sites that rely mainly on self-reporting methods and where third parties are not actively involved in the monitoring process. Finally, the case study presented in this paper demonstrates that with the appropriate satellite record, in situ measurements and field observations, remote sensing is a promising technology that can help monitor compliance with international environmental agreements.     

Hydrology and plant survival in excavated depressions near an earthen dam in north-central Texas

This investigation examined plant survival and water sources for small depressions excavated to build an earthen dam and nature trail in north-central Texas, USA. These “inadvertent wetlands” occupy part of an outdoor education facility, overlying alluvial deposits of the Trinity River. A large lake behind the earthen dam strongly influences surface water and groundwater levels in the area. Excavated depressions receive direct precipitation, runoff, and groundwater inputs, losing water by seepage and evapotranspiration. Hydroperiods varied with location and water input: excavations receiving groundwater held water year round; others periodically desiccated. Groundwater-fed depressions had higher salinity; however, the highest average value (1,304 μS/cm) was within the freshwater range. A total of 66 to 75% of emergent and floating wetland species planted in three depressions survived after 2 years. The developing wetlands appear viable under hydrologic conditions typical of the study period. Ultimately, variable hydroperiods among wetlands, and water level fluctuations within individual wetlands, may foster diverse plant-species compositions. Depressed lake levels following long-term drought or increased water demands pose the greatest threat to the developing wetlands.     

广州山水格局及其保护

广州“山水”的概念，不应仅仅理解为“云山珠水”。从越秀山、白云山起，向东北绵延200km的山脉，以及相辅的山丘台地，构成广州山的格局；广州的水，除了珠江以外，还应包括众多的河涌、湖泊、沼泽、滩涂等湿地。这些山地和湿地，对于广州的生态环境有十分重要的作用。保护和合理利用广州优越的山水条件，是建设现代化山水城市的必然要求。     

开发区建设与沿海湿地的保护──烟台夹河口沿海湿地的开发与保护剖析

湿地为陆地上常年或季节性积水以及过湿的土地，还包括低潮时水深不超过６ｍ的水域，并与其衍生的生物种群构成特有的生态系统。我国是世界上湿地类型多，分布广的国家之一，按面积是世界上第三湿地大国．我国对湿地开发利用的历史悠久，早在周代就有利用湿地植物资源的记载，然而对湿地较系统的成因、保护及资源持续利用的研究则是在本世纪６０年代才开始．近几年由于对外开放发展经济的需要，在沿海兴建经济开发区，对湿地产生了伤害。本文以烟台夹河口沿海湿地的成因及其受损情况为例，探讨沿海开发区建设与湿地保护的问题，并提出一些保护措施。     

Geochemical data as indicators of environmental change and human impact in sediments derived from downstream marshes of an ephemeral river,Northeast China

Recent sedimentary history of natural environmental change and anthropogenic influence in an ephemeral river catchment has been reconstructed using selected major and trace elements, element ratios, and their different geochemical phases (Tessier sequential extraction methods), pollen, and grain size combined with ²¹⁰Pb- and ¹³⁷Cs-dating method in marsh sedimentary cores. Attempts were made to use selected element ratios with different geochemical phases—residual phase of Ti, Al, V, Cr, Ni, Rb, K, Sr, and Ba; mobile Sr and Ba—combined with ²¹⁰Pb- and ¹³⁷Cs-chronology to interpret certain time information of environmental changes saved within the marsh sediments. Results indicate that there were two marked humid periods during 1850–1860 ad and 1890–1920 ad, and sand storm activities prevailed during 1920–1930 ad. After about 1900 ad, soil erosion has increased with the extensive agricultural activities in the Huolin River catchments, and further intensified after 1950s. After 1980, soil erosion has become even more intense, which is consistent with the reinforcement of human activities, the drastic loss of vegetation cover in the upstream lands, especially, the exploitation of the open cast coalmine in the upstream of Huolin River at that time. Influenced by the inundation of the Huolin River, the heavy metal pollution historical trends in Xianghai marsh wetland could be roughly divided into three periods by analysis of sediment enrichment factor (K_SEF) and the index of geoaccumulation (I _geo):1760–1880 ad, 1880–1980 ad, and 1980–now. Human activities accelerate the inputs of heavy metal, which leads to degradation of the marsh. This study also investigated on source of marsh sediments (by Ti/Al), redox condition [by V/Cr and V/(V + Ni)], and salinization indicators (by Sr/Ba and Rb/K). The results demonstrate that sources of sediments and redox conditions were partly similar for both riparian and depressional marshes. Besides, some differences in degree of salinization between two types of marsh were also identified, especially after 1880.     

Hydrochemical framework of the aquifer in and around East Kolkata Wetlands,West Bengal,India

The area lies between Hugli river in the northwest and Bidyadhari river in the east and includes the East Kolkata Wetlands. The East Kolkata Wetlands is included in the List of Wetlands of International Importance (“Ramsar List”), as per the Convention on Wetlands signed in Ramsar, Iran, in 1971. This wetland has been declared as a Ramsar site on the 19th August 2002 (Ramsar site no. 1208) and therefore has acquired an international status. The area is a part of the lower deltaic plain of the Bhagirathi–Ganga river system and is generally flat in nature. The sub-surface geology of the area is completely blanketed by the Quaternary fluviatile sediments comprising a succession of clay, silty clay, sand and sand mixed with occasional gravel. The Quaternary aquifer is sandwiched between two clay sequences. The confined aquifer is made up of moderately well sorted sand and reflects fluviatile environment of deposition. The regional groundwater flow direction is from east to west. Detailed geochemical investigations of 40 groundwater samples along with statistical analysis (for example, correlation and principal component analysis) on these chemical data reveal: (i) four types of groundwater quality, for example, good, poor, very poor and water unsuitable for drinking purpose, (ii) four hydrochemical facies which may be assigned to three broad types such as “fresh”, “blended”, and “brackish” waters, (iii) the evolution of the “blended” water is possibly due to hydraulic mixing of “fresh” and “brackish” waters within the aquifer matrix and/or in well mixing, and (iv) absence of Na–Cl facies indicates continuous flushing of the aquifer.     

Historical analogies as tools in understanding transformation

Historical analogies of environmental change and stress are a well-established method of examining vulnerability to the impacts of climate change. In our view historical analogies of social transformations can similarly illuminate what factors are conducive to transformation. In this paper we draw on the historical example of the environmental transformation of Aotearoa New Zealand from predominately woodlands into farmlands; a transformation which was inextricably linked with the social transformation of indigenous Māori society following European colonisation. The Aotearoa New Zealand case study illustrates how both incidental and purposeful transformations can be instigated by small groups of committed individuals working in formal or informal networks, but can also be imposed by outside experts who instituted widespread changes under notions of progress and improvement without local support or consent. Such transformations involved widespread changes to Indigenous governance regimes, agricultural systems, production and consumption patterns, lifestyles, values and worldviews, and inevitably involved both beneficial and negative outcomes for local peoples. We argue that thinking historically about transformational change provides an opportunity to assess the processes that shape both vulnerability and resilience, and the circumstances under which transformational change occurs, as well as the potential dangers of irreversible changes.     

Fine Resolution Palaeoecology Confirms Anthropogenic Impact During the Late Holocene in the Lower Hawkesbury Valley,NSW

This study reconstructs environmental conditions at Mill Creek, within the lower Hawkesbury-Nepean Valley, by the use of fine resolution palaeoecological studies of sediments. Archaeological surveys and historical accounts are used to investigate ecosystem response to known human activities. Research found that during prehistoric times (between 820 BP and the 1790s), the study area was well vegetated with dry sclerophyll communities on the valley sides, and a highly productive wetland community occupied the moist valley floor. Valley sides were generally stable, and little fire was evident in the landscape. Sediment was mainly deposited on the valley floor from the Hawkesbury-Nepean River during flood. After European settlement in the 1790s, sedimentation rates and charcoal preserved within sediments increased significantly, probably due to agricultural and clearing practices, both locally and upstream. Consequently, vegetation communities were altered. In 1967, the study area became part of Dharug National Park. Forestry and agricultural activities were excluded from the catchment, and the fire regime was reduced in frequency. Present-day vegetation communities appear to be becoming more like those that prevailed during prehistoric times. However, sedimentation rates remain elevated due to continued disturbance to the greater Hawkesbury River catchment. Recent poor water quality, coupled with a succession of floods on the Hawkesbury River, has increased wetland productivity levels, and their spatial extent, at Mill Creek.     

湿地缺水问题的研究展望

湿地是水循环的主体环节,从河流、湖泊、沼泽到河口以至近岸海区,都直接受水资源开发利用的影响。由于水资源传统的开发方式和过度利用,使湿地面临严重的缺水形势。为了保护湿地,维护流域水循环,我国已经开展了湿地生态需水研究,并取得一些成果。但是,如何保障湿地需水仍是摆在我们面前的重要课题。水权是水资源管理更加科学的分配制度,因此借助水权来探索生态需水的保障机制,使湿地生态需水得到可靠保证。