The spatial distribution of cropland is an important input to many applications including food security monitoring and economic land use modeling. Global land cover maps derived from remote sensing are one source of cropland but they are currently not accurate enough in the cropland domain to meet the needs of the user community. Moreover, when compared with one another, these land cover products show large areas of spatial disagreement, which makes the choice very difficult regarding which land cover product to use. This paper takes an entirely different approach to mapping cropland, using crowdsourcing of Google Earth imagery via tools in Geo-Wiki. Using sample data generated by a crowdsourcing campaign for the collection of the degree of cultivation and settlement in Ethiopia, a cropland map was created using simple inverse distance weighted interpolation. The map was validated using data from the GOFC-GOLD validation portal and an independent crowdsourced dataset from Geo-Wiki. The results show that the crowdsourced cropland map for Ethiopia has a higher overall accuracy than the individual global land cover products for this country. Such an approach has great potential for mapping cropland in other countries where such data do not currently exist. Not only is the approach inexpensive but the data can be collected over a very short period of time using an existing network of volunteers.
C. Müller, W. Cramer, W. L. Hare and H. Lotze-Campen, “Climate Change Risks for African Agriculture,” Proceedings of the National Academy of Sciences, Vol. 108, No. 11, 2011, pp. 4313-4315. doi:10.1073/pnas.1015078108
J. Knox, T. Hess, A. Daccache and T. Wheeler, “Climate Change Impacts on Crop Productivity in Africa and South Asia,” Environmental Research Letters, Vol. 7, No. 3, 2012, p. 034032. doi:10.1088/1748-9326/7/3/034032
FAO, “How to Feed the World in 2050. Report from the High-Level Expert Forum,” 2009.
J. A. Foley, N. Ramankutty, K. A. Brauman, E. S. Cassidy, J. S. Gerber, M. Johnston, N. D. Mueller, C. O’Connell, D. K. Ray, P. C. West, C. Balzer, E. M. Bennett, S. R. Carpenter, J. Hill, C. Monfreda, S. Polasky, J. Rockstrom, J. Sheehan, S. Siebert, D. Tilman and D. P. M. Zaks, “Solutions for a Cultivated Planet,” Nature, Vol. 478, No. 7369, 2011, pp. 337-342. doi:10.1038/nature10452
P. Smith, P. J. Gregory, D. van Vuuren, M. Obersteiner, P. Havlik, M. Rounsevell, J. Woods, E. Stehfest and J. Bellarby, “Competition for Land,” Philosophical Transactions of the Royal Society B: Biological Sciences, Vol. 365, No. 1554, pp. 2941-2957, Aug. 2010. doi:10.1098/rstb.2010.0127
FAO, “Land Cover and Land Use: The FAO AFRICOVER Programme,” 1998.
S. Fritz, E. Bartholomé, A. Belward, A. Hartley, H.-J. Stibig, H. Eva and P. Mayaux, “Harmonisation, Mosaicing and Production of the Global Land Cover 2000 Database (Beta Version),” Office for Official Publications of the European Communities, Luxembourg, 2003.
P. Bicheron, P. Defourny, C. Brockman, L. Schouten, C. Vancutsem, M. Huc, S. Bontemps, M. Leroy, F. Achard, M. Herold, F. Ranera and O. Arino, “GLOBCOVER,” 2008.
S. Fritz, L. See, I. McCallum, C. Schill, M. Obersteiner, M. van der Velde, H. Boettcher, P. Havlík and F. Achard, “Highlighting Continued Uncertainty in Global Land Cover Maps for the User Community,” Environmental Research Letters, Vol. 6, No. 4, 2011, Article ID: 044005. doi:10.1088/1748-9326/6/4/044005
J. Howe, “The Rise of Crowdsouring,” Wired Magazine, 2006.
“Amazon Mechanical Turk,” Wikipedia, the Free Encyclopedia, 2013.
G. Milcinski, “The Rise of Crowd-Sourcing: How Valuable Data Can We Get out of VGI,” CAPIGI, Amsterdam, 2011.
M. F. Goodchild and J. A. Glennon, “Crowdsourcing Geographic Information for Disaster Response: A Research Frontier,” International Society for Digital Earth, Vol. 3, No. 3, 2010, pp. 231-241.
D. G. Delaney, C. D. Sperling, C. S. Adams and B. Leung, “Marine Invasive Species: Validation of Citizen Science and Implications for National Monitoring Networks,” Biological Invasions, Vol. 10, No. 1, 2007, pp. 117-128. doi:10.1007/s10530-007-9114-0
D. Clery, “Galaxy Zoo Volunteers Share Pain and Glory of Research,” Science, Vol. 333, No. 6039, 2011, pp. 173-175. doi:10.1126/science.333.6039.173
M. F. Goodchild, “Citizens as Sensors: The World of Volunteered Geography,” GeoJournal, Vol. 69, No. 4, 2007, pp. 211-221. doi:10.1007/s10708-007-9111-y
P. Neis, D. Zielstra and A. Zipf, “The Street Network Evolution of Crowdsourced Maps: Open Street Map in Germany 2007-2011,” Future Internet, Vol. 4, No. 4, 2011, pp. 1-21. doi:10.3390/fi4010001
S. Fritz, I. McCallum, C. Schill, C. Perger, R. Grillmayer, F. Achard, F. Kraxner and M. Obersteiner, “Geo-Wiki.Org: The Use of Crowdsourcing to Improve Global Land Cover,” Remote Sensing, Vol. 1, No. 3, 2009, pp. 345-354. doi:10.3390/rs1030345
S. Fritz, I. McCallum, C. Schill, C. Perger, L. See, D. Schepaschenko, M. van der Velde, F. Kraxner and M. Obersteiner, “Geo-Wiki: An Online platform for Improving Global Land Cover,” Environmental Modelling & Software, Vol. 31, 2012, pp. 110-123. doi:10.1016/j.envsoft.2011.11.015
S. Fritz, L. See, M. van der Velde, R. A. Nalepa, C. Perger, C. Schill, I. McCallum, D. Schepaschenko, F. Kraxner, X. Cai, X. Zhang, S. Ortner, R. Hazarika, A. Cipriani, C. Di Bella, A. H. Rabia, A. Garcia, M. Vakolyuk, K. Singha, M. E. Beget, S. Erasmi, F. Albrecht, B. Shaw and M. Obersteiner, “Downgrading Recent Estimates of Land Available for Biofuel Production,” Environmental Science & Technology, Vol. 47, No. 3, 2013, pp. 1688-1694.
F. Albrecht, C. Perger, C. Schill, L. See, I. McCallum, R. Collins and S. Fritz, “Using Crowdsourcing to Examine Land Acquisitions in Ethiopia,” GI Forum, Salzburg, 2013.
W. Anseeuw, M. Boche, T. Breu, M. Giger, J. Lay, P. Messerli and K. Nolte, “Transnational Land Deals for Agriculture in the Global South. Analytical Report Based on the Land Matrix Database,” CDE/CIRAD/GIGA, Bern/ Montpellier/Hamburg, 1, 2012.
GOFC-GOLD, “GOFC-GOLD Reference Data Portal,” 2013. http://www.gofcgold.wur.nl/sites/gofcgold_refdataportal.php
P. Gong, J. Wang, L. Yu, Y. Zhao, Y. Zhao, L. Liang, Z. Niu, X. Huang, H. Fu, S. Liu, C. Li, X. Li, W. Fu, C. Liu, Y. Xu, X. Wang, Q. Cheng, L. Hu, W. Yao, H. Zhang, P. Zhu, Z. Zhao, H. Zhang, Y. Zheng, L. Ji, Y. Zhang, H. Chen, A. Yan, J. Guo, L. Yu, L. Wang, X. Liu, T. Shi, M. Zhu, Y. Chen, G. Yang, P. Tang, B. Xu, C. Giri, N. Clinton, Z. Zhu, J. Chen and J. Chen, “Finer Resolution Observation and Monitoring of Global Land Cover: First Mapping Results with Landsat TM and ETM+ Data,” International Journal of Remote Sensing, Vol. 34, No. 7, 2013, pp. 2607-2654.
C. Perger, S. Fritz, L. See, C. Schill, M. van der Velde, I. McCallum and M. Obersteiner, “A Campaign to Collect Volunteered Geographic Information on Land Cover and Human Impact,” In: T. Jekel, A. Car, J. Strobl and G. Griesebner, Eds., GI_Forum 2012: Geovisualisation, Society and Learning, Herbert Wichmann Verlag, Berlin/Offenbach, 2012, pp. 83-91.
W. Tobler, “A Computer Movie Simulating Urban Growth in the Detroit Region,” Economic Geography, Vol. 46, No. 2, 1970, pp. 234-240. doi:10.2307/143141
Reliefweb, “Ethiopia: Hararghe Food Security Hampered by Long-Term Drought Conditions and Economic Constraints,” 2003.