Wetlands are among the most productive areas of the planet, but they are also among the most endangered. Indeed, because of their high productivity, they are extremely rich in biodiversity (fauna and flora) and provide a large number of services for people, called ‘ecosystem services’, divided into three categories: regulating services, supporting services, and cultural services. Many ecosystem services are related to wetlands, such as: flood protection, climate change mitigation, freshwater provision, and public involvement for recreation and tourism purposes (Burkhard et al., 2014).
Remote sensing for monitoring and conservation
Despite these proven facts, the decline in wetland surface, estimated at 50% since the 1900s in the Mediterranean region (MWO, 2012), continues today throughout the world. This surface decline leads to a loss, sometimes irreversible, of biodiversity and benefits for humans. Many national and international actions are being put in place to stop this loss, one of which is acquiring Ramsar status for the wetlands. The Ramsar Convention (1971, Iran) highlights Wetlands of International Importance according to nine criteria specific to the type of wetland, habitats, and animal populations inventoried on site (mainly waterbirds and fish). The status of a Wetland of International Importance is achieved if the proposed site meets at least one of the nine criteria defined by the Ramsar Convention.
Nevertheless, the lack of knowledge about the functionalities of wetlands and their physicochemical and ecological evolution over time makes them poorly understood ecosystems around the world. The data acquired in the field do not always make it possible to quantify the evolution of the wetland surfaces over time as well as their physicochemical parameters, nor to arrive at a complete inventory on a large scale. New technologies, such as remote sensing, are therefore involved in complementing knowledge and understanding the functioning of wetlands on a national or international scale.
Special remote sensing is a term that emerged in 1971 following the launch of the first satellite dedicated to the observation of terrestrial natural resources (Landsat-1). This discipline encompasses all the tools for acquiring, remotely, information on the Earth’s surface. The information is extracted from images of earth-orbiting satellites or aerial photos acquired from overflights by airplane. Remote sensing has the capacity to provide key information for wetland conservation, and thus many national and international projects have emerged in recent years.
Here is a quick review:
The GLOBWETLAND I project (2003-2008)
The European Space Agency (ESA), with the help of the Ramsar Convention Secretariat, launched the GlobWetland I project in 2003 to demonstrate the relevance of satellite imagery and Earth Observation technologies, integrated with geographic information systems for the inventory, monitoring and evaluation of wetland ecosystems.
This project was carried out from 2003 to 2008, in collaboration with several conservation organizations and wetland managers. A total of 52 wetlands in 21 countries on four continents were studied. The GlobWetland I project has demonstrated that satellite technologies are proving to be productive and effective tools for supporting the Ramsar Convention and the Contracting Parties.
More information here: www.globwetland.org/
The GLOBWETLAND II project (2010 – 2014)
The most important follow-up to the GlobWetland I project is the launch of GlobWetland II. This project aims at inventorying wetlands in the Mediterranean basin, identifying threats to sites, and producing maps summarizing information extracted from satellite images over three different periods (1975, 1990, 2005 ). From a large number of types of satellite images (Landsat, Sentinel-2, RapidEye and SPOT), the tool allow researchers and managers to follow several parameters:
- Changes in land use
- The evolution of the surface of both natural and artificial wetlands
- The main pressures on wetlands.
The maps were made of more than 200 selected sites on the coastal wetlands of the watersheds of the southern and eastern Mediterranean countries, from Morocco to Syria, all of them less than 100 km from the coast. The GLOBWETLAND II tool thus makes it possible to follow the evolution of the surface of wetlands, to highlight changes in land use (e.g., evolution of urban and agricultural sprawl, loss of natural habitat), and to follow the evolution of the flooded area of coastal wetlands over time.
More information here: www.globwetland.org/
Thanks to this project, the Mediterranean Wetlands Observatory (MWO) was able to analyze the maps produced and complete the study for the northern shore of the Mediterranean (from Turkey to Portugal). This work produced a report on Land Use – Spatial Dynamics from 1975 to 2005 in Mediterranean coastal wetlands. The assessment shows that Mediterranean wetlands have on average had their natural habitat area reduced by 10% between 1975 and 2005 for the following reasons: the extension of the urban and agricultural environment, the increase in water abstraction, the construction of water reservoirs (dams), and marine erosion causing the retreat of the coastline.
- The second thematic report “Land cover spatial dynamics in Mediterranean coastal wetlands from 1975 to 2005”.
- The synthesis of “High-profile wetlands: Land cover in Ramsar Sites in Metropolitan France”.
SWOS (Satellite-based Wetland Observation Service, 2015-2018)
The SWOS project, funded by the European Horizon 2020 program, aims to create a remote sensing tool for monitoring wetlands based on indicators. As a first step, the first SWOS products, available in the form of maps for selected test sites, have been made available online to the general public.
In a second step, a remote sensing tool with many functionalities and applicable on many types of satellite images (Sentinel-1, 2 and 3, Landsat 1 to 8, Enviset MERIS and MODIS), as well as several indicators, will be made available to politicians and managers, along with a tutorial on its use. The SWOS remote sensing tool, which can be used from mapping (QGis, ArcGis) and the associated indicators allow the extraction of data related to wetlands and the production of different types of maps related to the following themes:
- Changes in land use
- Physicochemical parameters of water
- The dynamics of surface waters
- Soil moisture
- The capacity of habitats to provide ecosystem services (example: flood regulation)
This tool has been tested on 25 sites, located in 19 countries spread over three continents, and has highlighted, among other things, the evolution over time of wetlands and the threats they face. These results are then intended to enable managers and policies to adapt management practices or implement restoration measures on the concerned wetlands.
Learn more about the SWOS project here.
The RhoMéO project, supported by the Rhône Méditerranée Corse Water Agency and the Auvergne-Rhône-Alpes Region, is designed to implement remote sensing tools for the monitoring of wetlands in the Rhône-Mediterranean basin. The tool was built using 13 indicators, calculated from biological and physicochemical data collected in the field and information extracted from satellite images (Landsat 5 TM and Landsat 7 ETM +), and then applied to 200 test sites in the Provence-Alpes-Côte d’Azur region. The implementation of the indicators makes it possible to identify the wetlands and to highlight their biological and physicochemical state and the pressures they undergo. The tool, which can be used from the GIS ArcGis software, is available online to managers of natural areas in the Rhône-Mediterranean Basin accompanied by tutorials for users.
Learn more about the RhoMéO project here.
Flood Project (2015-2018)
The flood project, initiated in 2015 by the Tour du Valat and currently being finalized, aims to develop a remote sensing tool enabling the completion of a comprehensive inventory of Mediterranean wetlands. The developed tool will provide information on flooded areas over time and water quality across the Mediterranean basin. When pushed to its optimum, the tool will be able to differentiate the temporarily flooded areas from the wetlands themselves. In a second step, this work will also contribute to the development of two Mediterranean Wetland Observatory indicators related to wetlands: the indicator “degree of flooding of wetlands” and the future indicator of eutrophication of the environment. The result obtained will contribute to the construction of the MWO database, gathering all the available data on the Mediterranean wetlands, intended to be made available to a part of the public via a Web Mapping site.
The new remote sensing tools bring a real plus to the conservation of wetlands. They make it possible to acquire data that are difficult to measure in the field and over large geographical scales. The outcome of the projects mentioned above is to make the tools and data produced available to politicians and managers to enable everyone to gain knowledge on the functioning and role of wetlands in order to achieve conservation objectives.
Mr Anis Guelmami, Tour du Valat
- Mediterranean Wetlands Observatory (2014). Land cover – Spatial dynamics in Mediterranean coastal wetlands from 1975 to 2005. Thematic file N° 2. Tour du Valat, France. 48 pages. ISBN: 2-910368-59-9.
- Sanchez A., Abdul Malak D., Guelmami A., Perennou C. (2015). Development of an Indicator to Monitor Mediterranean Wetlands. PLoS ONE 10 (3): e0122694.
- Brochure of Satellite-based Wetland Observation Service (SWOS)
- Globwetland II handbook: “a regional pilot project of the Ramsar Convention on Wetlands”
- Burkhard B., Kandziora M., Hou Y. and Müller F. (204). “Ecosystem Service Potentials, Flows and Demands – Concepts for Spatial Localization, Indication and Quantification”; Landscape Online, p. 32, 2014.
- Mediterranean Wetlands Observatory (MWO) (202). “Mediterranean wetlands: challenges and prospects”; Technical report, Tour du Valat, France, 128p., 2012.