Next-generation soil information system of Africa at 250 m resolution published

Comparison of predicted soil organic carbon content (fine earth) for an area around the town of Arusha (Tanzania): SoilGrids1km (left) and AfSoilGrids250m (right).

In Africa, significant amounts of soil nutrients are lost every year due to inappropriate or unsustainable soil management practices. The Montpellier Panel has estimated that the economic loss in Africa due to poverty, climate change, population pressures and inadequate farming techniques is about 68 billion USD per year. This is considered to partially be the result of insufficient use of soil management knowledge. To help bridge the soil information gap on the African continent, ISRIC - World Soil Information, in collaboration with the Earth Institute, Columbia University, World Agroforestry Centre, Nairobi and the International Center for Tropical Agriculture (CIAT), has produced predictions of various soil properties for the whole African continent at 250 m spatial resolution at multiple standard soil depths. This product is referred to as the "AfSoilGrids250m" data set and is one of the main deliverables in 2015 of the Africa Soil Information Services project (AfSIS).

AfSIS project, funded by the Bill and Melinda Gates foundation and the Alliance for a Green Revolution in Africa (AGRA), aims at improving the way that soils are evaluated, mapped, and monitored, while at the same time significantly reducing the costs to do so.

AfSoilGrids250m is based on an automated system for soil mapping. Spatial predictions will be constantly updated as the new point data / new covariates arrive. (Click for larger picture)

The AfSoilGrids250m maps were produced using an automated system for soil mapping and make use of ISRIC's Global Soil Information Facilities framework. Spatial predictions have been generated using a combination of random forests and geostatistics (see scheme). In this framework, accuracy of predictions is constantly improved as the new data arrives (hence predictions are constantly updated in any automated system). At the heart of this crowdsourcing system is the user community that contributes new ground observations and rates the content and validates predictions. Results of the accuracy assessment of AfSoilGrids250m, have been reported in the PLOS One article (under review) Africa is now among first continents in the world for which free-access high resolution 3D soil property maps are available.

Possible uses of these maps include:

  • Soil-environmental modelling, land degradation studies, soil-landscape planning, biodiversity assessment (continental scale or country scale models);
  • General assessment of soil characteristics (baselines) for the African continent (e.g. total carbon stock),
  • Input to planning of new soil surveys / new soil sampling campaigns;
  • Downscaling and/or merging of coarse resolution maps with finer resolution maps (100 m, 30 m);

The AfSoilGrids250m data (GeoTIFFs) are available for download under the CC BY-NC. Total land area mapped is about 21 million square-kilometers. Each GeoTiff is about 29,501 columns by 31,505 rows and contains about 331 million pixel-values.

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