Global extent and distribution of wetlands: trends and issues

2018 ◽  
Vol 69 (4) ◽  
pp. 620 ◽  
Author(s):  
N. C. Davidson ◽  
E. Fluet-Chouinard ◽  
C. M. Finlayson
Keyword(s):  
High Spatial Resolution ◽  
Wetland Loss ◽  
Grand Challenge ◽  
Temporary Wetlands ◽  
Wetland Area ◽  
Time Period ◽  
Global Mapping ◽  
Real Increase ◽  
The Caribbean ◽  
Global Inventory

Herein we review estimates of global and regional wetland area from ‘bottom-up’ approaches of site or national wetland inventories and ‘top-down’ approaches from global mapping and remote sensing. The trend for increasing wetland extent reported in the literature over time is a consequence of improved mapping technologies and methods rather than a real increase in wetland area, because a continuing trend for natural wetland loss and conversion is documented over the same time period. The most recent high-resolution estimate of global wetland area is in excess of 12.1×106km2, of which 54% is permanently inundated and 46% is temporarily inundated. Globally, 92.8% of continental wetland area is inland and only 7.2% is coastal. Regionally, the largest wetland areas are in Asia (31.8%), North America (27.1%) and Latin America and the Caribbean (Neotropics; 15.8%), with smaller areas in Europe (12.5%), Africa (9.9%) and Oceania (2.9%). It is likely that estimates of global wetland area published to date persist in underestimating the true wetland area. The ‘grand challenge’ of a global inventory integrating all types of permanent and temporary wetlands at high spatial resolution has yet to be fully achieved.

Tsunami on Mars: Implications for the duration and timing of a northern ocean

2020 ◽  
Author(s):  
Francois Costard ◽  
José Alexis Palmero Rodriguez ◽  
Antoine Séjourné ◽  
Anthony Lagain ◽  
Steve Clifford ◽  
...  
Keyword(s):  
Climate Models ◽  
Northern Plains ◽  
The Past ◽  
Time Period ◽  
Total Inventory ◽  
Climatic Evolution ◽  
Global Inventory ◽  
The Impact ◽  
Equivalent Layer ◽  
Potential Origin

<p>The duration and timing of a northern ocean is a key issue in understanding the past geological and climatic evolution of Mars. Mars experienced its greatest loss of H<sub>2</sub>O between the Noachian and Late Hesperian (~10 m Global Equivalent Layer, Jakosky et al., 2017) roughly the same amount that is thought to have been added to the global inventory by extrusive volcanism over the same time period (Carr and Head, 2015). Thus, the total inventory of water was probably similar during these two epochs. But, the ocean during the Late Hesperian was smaller in extension than the ocean during the Noachian– with significant implications for the potential origin and survival of life. Here we examine the implications of the existence of a Late Hesperian/ Early Amazonian ocean on the planet’s inventory of water (and especially liquid water) and its variation with time. Our previous work (Rodriguez et al., 2016; Costard et al., 2017) concluded that the most plausible explanation for the origin of the Thumbprint Terrain (TT) lobate deposits, with run-ups, found along the dichotomy boundary, especially in Arabia Terra, was tsunami deposits. This supports the hypothesis that an ocean occupied the northern plains of Mars as recently as ~3 billion years ago. Furthermore, Costard et al (2017) produced a tsunami numerical model showing that the TT deposits exhibit fine-scale textural patterns due to the wave’s interference patterns resulting from interactions with the coastal topography. More recently, we suggested that the unusual characteristics of Lomonosov crater (50.52°N/16.39°E ) in the northern plains are best explained by the presence of a shallow ocean at the time of the impact (Costard et al., 2019). Interestingly, the apparent agreement between the age of the Lomonosov impact and that of the TT unit (~3 Ga), strongly suggests that it was the source of the tsunami (Costard et al., 2019). Our preliminary assessment indicates that this impact-generated tsunami required a mostly liquid ocean and because of the high latitude location of the Lomonosov crater site, our results strongly imply relatively warm paleoclimatic conditions. Our conclusions highlight the need for more sophisticated climate models.</p>

scholarly journals An evaluation of the potential of Sentinel 1 for improving flash flood predictions via soil moisture–data assimilation

2017 ◽  
Vol 44 ◽  
pp. 89-100 ◽  
Author(s):  
Luca Cenci ◽  
Luca Pulvirenti ◽  
Giorgio Boni ◽  
Marco Chini ◽  
Patrick Matgen ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Hydrological Model ◽  
High Spatial Resolution ◽  
Flash Flood ◽  
Soil Moisture Data ◽  
Time Period ◽  
The Impact

Abstract. The assimilation of satellite-derived soil moisture estimates (soil moisture–data assimilation, SM–DA) into hydrological models has the potential to reduce the uncertainty of streamflow simulations. The improved capacity to monitor the closeness to saturation of small catchments, such as those characterizing the Mediterranean region, can be exploited to enhance flash flood predictions. When compared to other microwave sensors that have been exploited for SM–DA in recent years (e.g. the Advanced SCATterometer – ASCAT), characterized by low spatial/high temporal resolution, the Sentinel 1 (S1) mission provides an excellent opportunity to monitor systematically soil moisture (SM) at high spatial resolution and moderate temporal resolution. The aim of this research was thus to evaluate the impact of S1-based SM–DA for enhancing flash flood predictions of a hydrological model (Continuum) that is currently exploited for civil protection applications in Italy. The analysis was carried out in a representative Mediterranean catchment prone to flash floods, located in north-western Italy, during the time period October 2014–February 2015. It provided some important findings: (i) revealing the potential provided by S1-based SM–DA for improving discharge predictions, especially for higher flows; (ii) suggesting a more appropriate pre-processing technique to be applied to S1 data before the assimilation; and (iii) highlighting that even though high spatial resolution does provide an important contribution in a SM–DA system, the temporal resolution has the most crucial role. S1-derived SM maps are still a relatively new product and, to our knowledge, this is the first work published in an international journal dealing with their assimilation within a hydrological model to improve continuous streamflow simulations and flash flood predictions. Even though the reported results were obtained by analysing a relatively short time period, and thus should be supported by further research activities, we believe this research is timely in order to enhance our understanding of the potential contribution of the S1 data within the SM–DA framework for flash flood risk mitigation.

How much wetland has the world lost? Long-term and recent trends in global wetland area

2014 ◽  
Vol 65 (10) ◽  
pp. 934 ◽  
Author(s):  
Nick C. Davidson
Keyword(s):  
Large Scale ◽  
Wetland Loss ◽  
Supporting Evidence ◽  
Ramsar Convention ◽  
Wetland Area ◽  
The World ◽  
Natural Wetlands ◽  
Recent Trends ◽  
National Governments

It has been frequently stated, but without provision of supporting evidence, that the world has lost 50% of its wetlands (or 50% since 1900 AD). This review of 189 reports of change in wetland area finds that the reported long-term loss of natural wetlands averages between 54–57% but loss may have been as high as 87% since 1700 AD. There has been a much (3.7 times) faster rate of wetland loss during the 20th and early 21st centuries, with a loss of 64–71% of wetlands since 1900 AD. Losses have been larger and faster for inland than coastal natural wetlands. Although the rate of wetland loss in Europe has slowed, and in North America has remained low since the 1980s, the rate has remained high in Asia, where large-scale and rapid conversion of coastal and inland natural wetlands is continuing. It is unclear whether the investment by national governments in the Ramsar Convention on Wetlands has influenced these rates of loss. There is a need to improve the knowledge of change in wetland areas worldwide, particularly for Africa, the Neotropics and Oceania, and to improve the consistency of data on change in wetland areas in published papers and reports.

scholarly journals Changes in Stream Peak Flow and Regulation in Naoli River Watershed as a Result of Wetland Loss

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Yunlong Yao ◽  
Lei Wang ◽  
Xianguo Lv ◽  
Hongxian Yu ◽  
Guofu Li
Keyword(s):  
Peak Flow ◽  
Daily Rainfall ◽  
Wetland Loss ◽  
Wetland Area ◽  
First Order ◽  
Rate Of Increase ◽  
Increasing Trend ◽  
Exponential Decay Model ◽  
Streamflow Data ◽  
Peak Streamflow

Hydrology helps determine the character of wetlands; wetlands, in turn, regulate water flow, which influences regional hydrology. To understand these dynamics, we studied the Naoli basin where, from 1954 to 2005, intensive marshland cultivation took place, and the watershed’s wetland area declined from94.4×104 ha to17.8×104 ha. More than 80% of the wetland area loss was due to conversion to farmland, especially from 1976 to 1986. The processes of transforming wetlands to cultivated land in the whole Naoli basin and subbasins can be described using a first order exponential decay model. To quantify the effects of wetlands cultivation, we analyzed daily rainfall and streamflow data measured from 1955 to 2005 at two stations (Baoqing Station and Caizuizi Station). We defined a streamflow regulation index (SRI) and applied a Mann-Kendall-Sneyers test to further analyze the data. As the wetland area decreased, the peak streamflow at the Caizuizi station increased, and less precipitation generated heavier peak flows, as the runoff was faster than before. The SRI from 1959 to 2005 showed an increasing trend; the SRI rate of increase was 0.05/10a, demonstrating that the watershed’s regulation of streamflow regulation was declined as the wetlands disappeared.

scholarly journals Analysing the Impact of Large Data Imports in OpenStreetMap

2021 ◽  
Vol 10 (8) ◽  
pp. 528
Author(s):  
Raphael Witt ◽  
Lukas Loos ◽  
Alexander Zipf
Keyword(s):  
Large Data ◽  
Heterogeneous Data ◽  
Geographical Information ◽  
Data Sets ◽  
Heterogeneous Data Source ◽  
External Data ◽  
Time Period ◽  
Global Mapping ◽  
Data Source ◽  
The Impact

OpenStreetMap (OSM) is a global mapping project which generates free geographical information through a community of volunteers. OSM is used in a variety of applications and for research purposes. However, it is also possible to import external data sets to OpenStreetMap. The opinions about these data imports are divergent among researchers and contributors, and the subject is constantly discussed. The question of whether importing data, especially large quantities, is adding value to OSM or compromising the progress of the project needs to be investigated more deeply. For this study, OSM’s historical data were used to compute metrics about the developments of the contributors and OSM data during large data imports which were for the Netherlands and India. Additionally, one time period per study area during which there was no large data import was investigated to compare results. For making statements about the impacts of large data imports in OSM, the metrics were analysed using different techniques (cross-correlation and changepoint detection). It was found that the contributor activity increased during large data imports. Additionally, contributors who were already active before a large import were more likely to contribute to OSM after said import than contributors who made their first contributions during the large data import. The results show the difficulty of interpreting a heterogeneous data source, such as OSM, and the complexity of the project. Limitations and challenges which were encountered are explained, and future directions for continuing in this field of research are given.

scholarly journals Wetland Biomass and Productivity in Coastal Louisiana: Base Line Data (1976–2015) and Knowledge Gaps for the Development of Spatially Explicit Models for Ecosystem Restoration and Rehabilitation Initiatives

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2054 ◽  
Author(s):  
Rivera-Monroy ◽  
Elliton ◽  
Narra ◽  
Meselhe ◽  
Zhao ◽  
...  
Keyword(s):  
Coastal Wetland ◽  
Net Primary Productivity ◽  
Simulation Models ◽  
Belowground Biomass ◽  
Wetland Loss ◽  
Base Line ◽  
Knowledge Gaps ◽  
Wetland Area ◽  
Research Issues ◽  
Coastal Louisiana

Coastal Louisiana hosts 37% of the coastal wetland area in the conterminous US, including one of the deltaic coastal regions more susceptible to the synergy of human and natural impacts causing wetland loss. As a result of the construction of flood protection infrastructure, dredging of channels across wetlands for oil/gas exploration and maritime transport activities, coastal Louisiana has lost approximately 4900 km2 of wetland area since the early 1930s. Despite the economic relevance of both wetland biomass and net primary productivity (NPP) as ecosystem services, there is a lack of vegetation simulation models to forecast the trends of those functional attributes at the landscape level as hydrological restoration projects are implemented. Here, we review the availability of peer-reviewed biomass and NPP wetland data (below and aboveground) published during the period 1976–2015 for use in the development, calibration and validation of high spatial resolution (<200 m × 200 m) vegetation process-based ecological models. We discuss and list the knowledge gaps for those species that represent vegetation community associations of ecological importance, including the long-term research issues associated to limited number of paired belowground biomass and productivity studies across hydrological basins currently undergoing different freshwater diversions management regimes and hydrological restoration priorities.

Loss of wetlands due to the expansion of polder in the Dongting Plain, China, AD 1368–1980

The Holocene ◽  
2020 ◽  
Vol 30 (5) ◽  
pp. 646-656
Author(s):  
Yikai Li ◽  
Yu Ye ◽  
Xiuqi Fang ◽  
Chengpeng Zhang ◽  
Zhilong Zhao
Keyword(s):  
Wetland Loss ◽  
Spatial Difference ◽  
Chronological Order ◽  
Wetland Area ◽  
The Past ◽  
Before And After ◽  
The Times ◽  
Wetland Losses ◽  
Over Time

The Dongting Plain is an area characterized by wetland losses because of long-term polder construction. The study of historical polder expansion provides an opportunity to better understand the loss of wetlands covered by polders. To reconstruct the polder expansion over time, the polder patches extracted though remote sensing were marked with the names obtained from maps and the times of construction obtained from local gazetteers, and shown in the chronological order of turning points. Then, the distribution and changes in the wetlands covered by polders during 1368–1980 were reconstructed. The following are the major findings: (1) the current polders (2010s) accumulated over many centuries. There were 5.7% of the current polder area in 1644, 14.0% in 1735, 23.4% in 1850, 55.0% in 1911, 73.6% in 1949, and 100% in 1980; (2) the wetlands were mostly lost in the northern part of the region and declined rapidly over the past two centuries. The wetland area in 1850 was 6635 km2, which in 1911, 1949 and 1980 were 73.9%, 62.7% and 40.6% of that in 1850, respectively; (3) there were differences in the rate of wetland loss. The fastest time of wetland area disappearance was in 1949–1980, and 45.8 km2 of the wetlands had been lost each year; and (4) there was a spatial difference in wetland losses caused by polder expansion. In the northern part of the area, the wetland loss was mainly in 1851–1980, and the polders constructed in this period covered 89.5% of the polder area. In contrast, in the southern part of the area, the change in the wetland area was relatively small in each period, and the polder constructed before and after 1850 covered 48.3% and 52.7% of the polder area, respectively.

scholarly journals Anthropogenic causes of wetland loss and degradation in the lower Kłodnica valley (southern Poland)

2015 ◽  
Vol 3 (4) ◽  
pp. 20-29 ◽  
Author(s):  
Krzysztof J. Wójcicki ◽  
Beata Woskowicz-Ślęzak
Keyword(s):  
Soil Erosion ◽  
Human Impact ◽  
Middle Ages ◽  
Environmental Issues ◽  
Global Scale ◽  
Wetland Loss ◽  
Water Levels ◽  
Wetland Area ◽  
Land Drainage ◽  
First Millennium

AbstractLoss and degradation of wetlands is now one of the most important environmental issues on a global scale. Previous research based on analyses of cartographic materials allow for quantification of changes in wetland area in recent centuries. The results of lithological research of peat cores, reported in this publication, have established that the processes of anthropogenic loss of wetlands can be much older and in the Kłodnica valley were initiated in the first millennium BC. As a result of increased mineral sedimentation accompanying soil erosion some peatlands have been fossilized whilst the area of others has been reduced. In total, the surface area of peat-forming wetlands in the bottom of the Kłodnica valley decreased by over 60% between the time of the Lusatian Culture settlement and the Middle Ages. Post-peatland habitats are recently used for agricultural or colonized by non-peat forming vegetation. These processes have played a more important role in the degradation of peatland ecosystems than the direct human impact in historic times. Changes in hydrographic networks, land drainage and regulation of water levels in rivers and canals in the last century have contributed to further reducing the wetland areas by almost 50% compared to the 1880s. These processes, however, have mainly affected ephemeral non-peat forming wetlands.

scholarly journals Mapping Mangrove Extent and Change: A Globally Applicable Approach

2018 ◽  
Vol 10 (9) ◽  
pp. 1466 ◽  
Author(s):  
Nathan Thomas ◽  
Peter Bunting ◽  
Richard Lucas ◽  
Andy Hardy ◽  
Ake Rosenqvist ◽  
...  
Keyword(s):  
French Guiana ◽  
High Spatial Resolution ◽  
Image Method ◽  
Total Change ◽  
Alos Palsar ◽  
Policy Makers ◽  
Mangrove Area ◽  
East Kalimantan ◽  
Time Period ◽  
Change Threshold

This study demonstrates a globally applicable method for monitoring mangrove forest extent at high spatial resolution. A 2010 mangrove baseline was classified for 16 study areas using a combination of ALOS PALSAR and Landsat composite imagery within a random forests classifier. A novel map-to-image change method was used to detect annual and decadal changes in extent using ALOS PALSAR/JERS-1 imagery. The map-to-image method presented makes fewer assumptions of the data than existing methods, is less sensitive to variation between scenes due to environmental factors (e.g., tide or soil moisture) and is able to automatically identify a change threshold. Change maps were derived from the 2010 baseline to 1996 using JERS-1 SAR and to 2007, 2008 and 2009 using ALOS PALSAR. This study demonstrated results for 16 known hotspots of mangrove change distributed globally, with a total mangrove area of 2,529,760 ha. The method was demonstrated to have accuracies consistently in excess of 90% (overall accuracy: 92.2–93.3%, kappa: 0.86) for mapping baseline extent. The accuracies of the change maps were more variable and were dependent upon the time period between images and number of change features. Total change from 1996 to 2010 was 204,850 ha (127,990 ha gain, 76,860 ha loss), with the highest gains observed in French Guiana (15,570 ha) and the highest losses observed in East Kalimantan, Indonesia (23,003 ha). Changes in mangrove extent were the consequence of both natural and anthropogenic drivers, yielding net increases or decreases in extent dependent upon the study site. These updated maps are of importance to the mangrove research community, particularly as the continual updating of the baseline with currently available and anticipated spaceborne sensors. It is recommended that mangrove baselines are updated on at least a 5-year interval to suit the requirements of policy makers.

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