A Sharper Look at the World’s Rivers and Catchments

Rivers are the arteries of the planet, providing vital resources as they flow and pulse across landscapes in a vast global network. Rivers and streams convey sediments and nutrients to fertile valleys and river deltas, create habitat corridors and transportation routes, and deliver life-sustaining fresh water to aquatic and riparian ecosystems and to human populations. In the absence of a universally accepted digital global river network, the HydroSHEDS database has emerged in the past decade as the most frequently applied global hydrographic mapping product, supporting a large and growing community of users. Soon this community will have access to a new version of HydroSHEDS offering expanded capabilities and promising clearer views of Earth’s arteries. HydroSHEDS version 2 (also called HydroSHEDS-X), currently under development, will offer substantial revisions and improvements on version 1 while following the same design characteristics to ensure maximum compatibility between versions and to related products. The new version is derived from the TanDEM-X (TerraSAR-X add-on for digital elevation measurement) global elevation model, which was created in partnership between the German Aerospace Center (DLR) and Airbus, and is superior to the SRTM DEM in several ways. The elevation data of TanDEM-X were produced at an original resolution of 12 meters, and they cover the entire global land surface area, including northern latitudes. To enhance the quality of results while retaining spatial compatibility, HydroSHEDS-X has been created from the original, nonpublic 12-meter-resolution version of TanDEM-X, yet it will be released at the same 3-arc-second resolution as HydroSHEDS version 1. This approach ensures fully global, homogeneous coverage, including of areas above 60°N latitude, at substantially improved quality due to both the finer resolution of the underpinning DEM and the reduced need to fill data gaps compared with the SRTM data

Concordance of freshwater and terrestrial biodiversity

Efforts to set global conservation priorities have largely ignored freshwater diversity, thereby excluding some of the world\u27s most speciose, threatened, and valuable taxa. Using a new global map of freshwater ecoregions and distribution data for about 13,300 fish species, we identify regions of exceptional freshwater biodiversity and assess their overlap with regions of equivalent terrestrial importance. Overlap is greatest in the tropics and is higher than expected by chance. These high-congruence areas offer opportunities for integrated conservation efforts, which could be of particular value when economic conditions force conservation organizations to narrow their focus. Areas of low overlap-missed by current terrestrially based priority schemes-merit independent freshwater conservation efforts. These results provide new information to conservation investors setting priorities at global or regional scales and argue for a potential reallocation of future resources to achieve representation of overlooked biomes. © 2010 Wiley Periodicals, Inc

The new hydrographic HydroSHEDS database derived from the TanDEM-X DEM

Water-related applications such as hydrology, hydrodynamics, and flood inundation modelling crucially require fundamental hydrographic knowledge and monitoring as well as the tools and data that support mapping and analysis of natural river and drainage characteristics. Since its introduction in 2008, HydroSHEDS is a well-established database providing seamless hydrographic information to support hydro-ecological research and applications on a multitude of scales by offering standardized spatial units for hydrological assessments. Although being widely used, the Shuttle Radar Topography Mission (SRTM)-based version 1 of HydroSHEDS has important limitations, in particular in areas above 60° N latitude. A steadily increasing availability and accuracy of remote sensing data promotes the development of a second and refined version of HydroSHEDS, which is based on the globally consistent and highly accurate TanDEM-X dataset. In light of this, HydroSHEDS v2 is currently created in collaboration between the German Aerospace Center (DLR), McGill University, Confluvio Consulting and the World Wildlife Fund. Within the HydroSHEDS workflow, the pre-conditioning comprises multiple editing and correction steps to prepare the TanDEM-X DEM for hydrological applications. Compared to HydroSHEDS v1, the resulting hydrologically conditioned DEM ensures a more accurate derivation of HydroSHEDS v2 core products such as flow directions, river courses and catchment boundaries. By providing even clearer and more complete views of Earth’s waterways, the HydroSHEDS geospatial framework serves various management and decisionmaking applications beyond scientific research including aquatic ecosystem services, human health impacts and conservation planning

Global Dam Watch: curated data and tools for management and decision making

Dams, reservoirs, and other water management infrastructure provide benefits, but can also have negative impacts. Dam construction and removal affects progress toward the UN sustainable development goals at local to global scales. Yet, globally-consistent information on the location and characteristics of these structures are lacking, with information often highly localised, fragmented, or inaccessible. A freely available, curated, consistent, and regularly updated global database of existing dams and other instream infrastructure is needed along with open access tools to support research, decision-making and management needs. Here we introduce the Global Dam Watch (GDW) initiative (www.globaldamwatch.org ) whose objectives are: (a) advancing recent efforts to develop a single, globally consistent dam and instream barrier data product for global-scale analyses (the GDW database); (b) bringing together the increasingly numerous global, regional and local dam and instream barrier datasets in a directory of databases (the GDW directory); (c) building tools for the visualisation of dam and instream barrier data and for analyses in support of policy and decision making (the GDW knowledge-base) and (d) advancing earth observation and geographical information system techniques to map a wider range of instream structures and their properties. Our focus is on all types of anthropogenic instream barriers, though we have started by prioritizing major reservoir dams and run-of-river barriers, for which more information is available. Our goal is to facilitate national-scale, basin-scale and global-scale mapping, analyses and understanding of all instream barriers, their impacts and their role in sustainable development through the provision of publicly accessible information and tools. We invite input and partnerships across sectors to strengthen GDW’s utility and relevance for all, help define database content and knowledge-base tools, and generally expand the reach of GDW as a global hub of impartial academic expertise and policy information regarding dams and other instream barriers

The Living Planet Index (LPI) for migratory freshwater fish:Technical Report

Migratory freshwater fish (i.e. fish that use freshwater systems, either partly or exclusively) occur around the world and travel between critical habitats to complete their life cycle. They are disproportionately threatened compared to other fish groups but global trends in abun-dance, regional differences and drivers of patterns have not yet been comprehensively described. Using abundance information from the Living Planet Database, we found widespread declines between 1970 and 2016 in tropical and temperate areas and across all regions, all migration categories and all populations. Globally, migratory freshwater fish have declined by an average of 76%. Average declines have been more pronounced in Europe (-93%) and Latin America & Caribbean (-84%), and least in North America (-28%). The percentage of species represented was highest in the two temperate regions of Europe and North America (almost 50%). For the continents of Africa, Asia, Oceania, and South America, data was highly deficient, and we advise against making conclusions on the status of migratory freshwater SUMMARYfish in these areas. Potamodromous fish, have declined more than fish migrating between fresh and salt water on average (-83% vs -73%). Populations that are known to be affected by threats anywhere along their migration routes show an average decline of 94% while those not threatened at the population level have increased on av-erage. Habitat degradation, alteration, and loss accounted for around a half of threats to migratory fish, while over-exploitation accounted for around one-third. Protected, regulated and exploited populations decreased less than unmanaged ones, with the most often recorded actions being related to fisheries regulations, including fishing restrictions, no-take zones, fisheries closures, bycatch reductions and stocking (these were most com-mon in North America and Europe). Recorded reasons for observed increases tended to be mostly unknown or un-described, especially in tropical regions. This information is needed to assemble a more complete picture to assess how declines in migratory freshwater fishes could be reduced or reversed. Our findings confirm that migratory freshwater fish may be more threatened throughout their range than previously documented

Bending the curve of global freshwater biodiversity loss: an emergency recovery plan

Despite their limited spatial extent, freshwater ecosystems host remarkable biodiversity, including one-third of all vertebrate species. This biodiversity is declining dramatically: Globally, wetlands are vanishing three times faster than forests, and freshwater vertebrate populations have fallen more than twice as steeply as terrestrial or marine populations. Threats to freshwater biodiversity are well documented but coordinated action to reverse the decline is lacking. We present an Emergency Recovery Plan to bend the curve of freshwater biodiversity loss. Priority actions include accelerating implementation of environmental flows; improving water quality; protecting and restoring critical habitats; managing the exploitation of freshwater ecosystem resources, especially species and riverine aggregates; preventing and controlling nonnative species invasions; and safeguarding and restoring river connectivity. We recommend adjustments to targets and indicators for the Convention on Biological Diversity and the Sustainable Development Goals and roles for national and international state and nonstate actors

Freshwater ecoregions of the world: A new map of biogeographic units for freshwater biodiversity conservation

We present a new map depicting the first global biogeographic regionalization of Earth's freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the world's freshwaters through a new framework.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Naturales y Muse