https://orcid.org/0000-0001-9947-2945
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ABSTRACT
Exacerbated by climate change, Europe has experienced series of hot and dry summer since the beginning of the 21st century. The importance of land conditions became an international concern with a dedicated sustainable development goal (SDG), the SDG 15. It calls for developing and finding innovative solutions to follow and evaluate impacts of changing land conditions induced by various driving forces. In Switzerland, drought risk will significantly increase in the coming decades with severe consequences on agriculture, energy production and vegetation. In this paper, we used a 35-year satellite-derived annual and seasonal times-series of normalized difference water index (NDWI) to follow vegetation water content evolution at different spatial and temporal scales across Switzerland and related them to temperature and precipitation to investigate possible responses of changing climatic conditions. Results indicate that there is a small and slow drying tendency at the country scale with a NDWI mean decreasing slope of −0.22%/year for the 23% significant pixels across Switzerland. This tendency is mostly visible below 2000 m above sea level (m.a.s.l.) and in all biogeographical regions. The Southern Alps regions appear to be more responsive to changing drying conditions with a significant and slight negative NDWI trend (−0.39%/year) over the last 35 years. Moreover, NDWI values are mostly a function of temperature at elevations below the tree line rather than precipitation. Findings suggest that multi-annual and seasonal NDWI can be a valuable indicator to monitor vegetation water content at different scales, but other components such as land cover type and evapotranspiration should be considered to better characterize NDWI variability. Satellite Earth Observations data can provide valuable complementary observations for national statistics on the ecological state of vegetation to support SDG 15 to monitor land affected by drying conditions.
Acknowledgments
The views expressed in the paper are those of the authors and do not necessarily reflect the views of the institutions they belong to.
This research was funded by European Commission “Horizon 2020 Program” ERA-PLANET/GEOEssential project, grant number 689443.
Results of this publication are partly or fully relying on the Swiss Data Cube (http://www.swissdatacube.org), operated and maintained by UN Environment/GRID-Geneva, the University of Geneva, the University of Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research WSL.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The NDWI time-series data that support the findings of this study are openly available at https://doi.org/10.26037/yareta:xzczpcai2nbp5l4na7rx2oelse and https://doi.org/10.26037/yareta:bwtgg2z5cbhf3e47rugqhmhgui. Temperature (TabsM and TabsY) and precipitation (RhiresM and RhiresY) dataset from the MeteoSwiss platform – Spatial Climate Analysis data are available for registered users at: https://www.meteoswiss.admin.ch/home/climate/swiss-climate-in-detail/raeumliche-klimaanalysen.html.
Additional information
Notes on contributors
Charlotte Poussin
Charlotte Poussin is a PhD student at the University of Geneva/Institute for Environmental Sciences & GRID-Geneva. Her research topic is on assessing and monitoring the impacts of climate change in Switzerland using time series analyses in the Swiss Data Cube.
Alexandrine Massot
Alexandrine Massot is an MSc student at the University of Geneva/Institute for Environmental Sciences on Biodiversity and Climate Change.
Christian Ginzler
Dr. Christian Ginzler is a senior scientist and team leader of the Land Change Science Remote Sensing group at Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). He manages projects of remote sensing tasks of nation-wide monitoring programms (e.g., Swiss National Forest Inventory, Biotopmonitoring Switzerland). His research interests include digital photogrammetry, digital surface models and applied remote sensing.
Dominique Weber
Dominique Weber is a technical staff member of the Land Change Science Remote Sensing group at Swiss Federal Institute for Forest, Snow and Landscape Research (WSL). He is an environmental scientist with special interest in remote sensing, ecology and conservation.
Bruno Chatenoux
Bruno Chatenoux is the Swiss Data Cube project scientists and analyst. Mr. Chatenoux is a civil-engineer and geologist specialized in GIS in environmental sciences. He joined UNEP/GRID-Geneva in 2005 to model the impact of the South-East Asia Tsunami according to environmental features. He has been involved on various projects such as the water quality and quantity modelling of lake Balaton (Hungary) with SWAT software, maintenance of the PREVIEW web application, natural hazard events and exposure modelling for the main one. He also worked as a consultant for the Small Arms Survey (SHBA project), and as a GIS advisor for the French Red Cross.
Pierre Lacroix
Dr. Pierre Lacroix is a senior scientist working at University of Geneva+ in the enviroSPACE laboratory (Institute for Environmental Sciences). He is also specialist in Spatial Data Infrastructure (SDI) at the United Nations Environment Science Division. He has worked in the private and public sectors, in France and in Switzerland, and has participated in various research projects at different geographical scales, from local to international, and in different domains such as water resource management, humanitarian demining and transparency in the extractives sector. He has been work package leader in FP7 IASON (iason-fp7.eu/) and is currently the technology manager of MAPX (mapping and assessing the performance of extractive industries:mapx.org). He holds a PhD in environmental sciences and is also civil engineer (French ‘Ecole+des+Mines’).
Thomas Piller
Thomas Piller has an MSc in geology and a GIS expert at UNEP/GRID-Geneva where he is involved in the MapX project.
Liliane Nguyen
Liliane Nguyen is a PhD student at the University of Geneva/Institute for Environmental Sciences in the Nonlinerarity and Climate group.
Gregory Giuliani
Dr. Gregory Giuliani is the Head of the Digital Earth Unit and Swiss Data Cube Project Leader at GRID-Geneva of the United Nations Environment Programme (UNEP) and a Senior Lecturer at the University of Geneva’s Institute for Environmental Sciences. He is a geologist and environmental scientist who specializes in Remote Sensing, Geographical Information Systems (GIS) and Spatial Data Infrastructures (SDI). He also works at GRID-Geneva of the United Nations Environment Programme (UNEP) since 2001, where he was previously the focal point for Spatial Data Infrastructure (SDI) and is currently the Head of the Digital Earth Unit. Dr. Giuliani's research focuses on Land Change Science and how Earth observations can be used to monitor and assess environmental changes and support sustainable development.