1 Background
Wetlands play a major role in the availability and quality of water. They are integral components in the hydrological cycle and contain most of the water utilized to meet human needs. The wise use of wetlands is essential for the delivery of sustainable water management that also promotes sustainable economic and social development.
The Ramsar Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an intergovernmental treaty that provides the political framework for international cooperation on the preservation and sustainable development of wetlands of international importance. There are presently 164 countries that have endorsed the Convention, with 2,083 wetland sites that count for a total more than million hectares.
The Ramsar Convention addresses the importance of developing and intensifying internationally coordinated actions for the conservation and wise use of wetlands. This requires that all communities involved in the implementation of the convention have up-to-date and reliable information to understand wetland areas better, complete national inventories, perform monitoring activities, carry out assessments and put appropriate management plans in practice.
The European Space Agency is contributing to this complex and challenging task with its GlobWetland II project. GlobWetland II contributes to the establishment of a Global Wetlands Observing System (G-WOS) in accordance with Ramsar’s 2009 - 15 strategic plan. The project is implemented in partnership with Ramsar, the MedWet initiative, Mediterranean Wetlands Observatory (MWO), and 10 countries from the Southern Mediterranean Basin (from Morocco to Jordan). It provides about 1800 maps and indicators for 200 wetlands located along the 10 participating countries, and a software toolbox to all partners.
2 Methods
The GW-II thematic mapping is based on Landsat images and consists of 3 different map types - Land Use/Land Cover maps (LULC), Change maps, Water Cycle Regime maps(WCR) and 4 indicators (Change in wetland areas, Inundation of the ecosystem, Change due to agriculture and urbanization, Status and trends of wetland threats) for 3 points in time (1975, 1990, 2000).
The first step of the satellite image processing is the ortho-rectification and matching of all Landsat data per test site. In a second step the satellite data will be radiometrically adapted. The methodology for radiometric adaptation is based on CVA and MAD. The next step, the LULC classification follows a supervised and segment-based approach.
The change maps will be processed in 2 steps, an automated change/no change masking to reduce the propagation of classification errors and a post classification comparison for the change labeling.
The water cycle regime methodology uses also an segment based and supervised classification, which is applied on the infrared channels of Landsat and on additional indexes like the water and vegetation index (MNDWI and NDVI).
The minimum mapping unit for all maps is 1 ha and will be constrained through the segmentation software.
All single processing steps are implemented with newly developed software tools and the tools that have been integrated in user friendly workflows and GUI's.
The map legend comprises the Corine Land cover classes together with the Ramsar typology. The change classes of the Land Cover Flow legend indicate the conversions that happen between two classes. It has been developed by EEA and modified in GW-II to highlight changes in wetland classes and conversions from wetland classes to agriculture or urban areas.
The indicator calculation uses GIS functionalities available in ArcGIS and is based on the prior calculated mapping results that are weighted in accordance to the distance of the land cover segments to the wetland.
3 Results
The GW-II toolbox has been developed and installed at different organizations of the 10 Mediterranean partner countries as well as at the Tour du Valat, host of the Mediterranean Wetlands Observatory (MWO). It is a new ArcGIS toolbox that provides ArcGIS toolbox menus, tool help, command line input and batch processing capability as well as modeler support In addition the software is available as a stand-alone version with an independent graphical user interface.
The new GW-II Software Toolbox integrated into ArcGIS
The toolbox is currently being used to produce the 1800 thematic maps in the 10 countries. The mapping results reveal that although, in general, wetland extents have gradually decreased mainly due to agriculture and urbanization pressures, there are still unaffected areas where changes are not large or even sometimes where wetlands’ extent has increased.
An example, Egypt’s Lake Burullus which is located within the Nile River Delta, has undergone major changes in the past decades.
Wetland monitoring in Egypt, Lake Burullus
Urban settlements have flourished around the lake, and from 1973 to 1990 the area saw a sharp increase in aquaculture. As a result of increased waste water in the lake (largely due to aquaculture), there has been an overall decrease of salt marsh vegetation in the lake itself, in some parts replaced by reed beds.
4. Future perspectives
The heads of the hosted organizations and policy makers from the 10 participating countries, as well as Ramsar and MedWet secretariats, have welcomed the GlobWetland II observing system to create standard and comparable geo-information products. As an example, the GW-II observation system has been recognized by the Agadir guidelines of the Medwet symposium as a major contribution to the development of a Global Wetland Observation System (G-WOS) and as a success story that demonstrates how the use of satellite-based earth observation tools can bring cost-effective and productive solutions for inventory, assessment and monitoring of water and wetlands. In addition cooperation with GW-II has been recommended to all Ramsar participating countries in the resolutions of the 11th Conference of the Parties of the Ramsar convention (Bucharest, July 2012).
Further analytical conclusions are anticipated by the involved countries and by the MWO. The MWO recently announced that they will continue the use of the GW-II toolbox to produce wetland maps and indicators over the remaining 17 Mediterranean countries of the MedWet initiative, with the objective to publish in 2014 a special report on the status and trends of wetlands in the Mediterranean basin.
In the future the monitoring of wetlands will largely benefit from the forthcoming Sentinel-2 mission. The large swath of the Sentinel-2 satellites, along with their short revisit time and extended multi-spectral-infrared channels , will allow for seasonal and permanent changes in wetlands to be accurately monitored.
