- Crop field boundary is an essential agricultural variable, and crop field sizes are indicative of the degree of agricultural capital investment, mechanization, and labor intensity.
- Information on delineated field boundaries and field sizes are needed for land use planning, allocation of resources, and agricultural modeling.
- Field extraction is extremely challenging in smallholder regions in Asia and Africa due to small field sizes, irregularly-shaped boundaries, narrow margins, and heterogeneities within and across fields.
- With commercial high-resolution images provided by NASA and new computer-vision algorithms, crop field boundaries are produced in smallholder regions in multiple countries in Asia.
- Agrarian transitions are studied based on characterization of field/farm size changes in multiple Asian countries.
How is land cover/use changed?
Agrarian transition, which refers to the transformation from an agrarian society to one based on industrial production and services, is occurring globally. Researchers hypothesized that per capita income rises, economies diversify, workers leave agriculture, rural wages increase, capital becomes cheaper relative to land and labor, and farmers consolidate their land into larger farms [1]. The history of agriculture suggests that as economies grow, farm sizes grow, but the transition pathways can vary for different countries, and the transition may not even occur [2]. From 1960 to 2000, while the average farm size increased in some upper-middle income countries and in nearly all high-income countries, it decreased in most low- and lower-middle income countries (not including China for having no data) [3].
Fig. 1: Field extraction from Maxar WorldView-3 image in a 6 × 6 km area in Bua Pak Tha subdistrict, Nakhon Pathom, central Thailand. Extracted fields are colored by sizes (blue: > 2 ha, green: 1-2 ha, orange/red: < 1 ha).
Why is this Important?
“Farm size has become a key variable of interest in discussions surrounding food security, development, and the environment” [4]. 84% of the 570 million farms in the world are < 2 ha, mostly in Asia and Africa [3]. However, there are no publicly-available field boundary data in these regions because field extraction is hard for small fields, and also because commercial high- resolution satellite images are not freely available.
How satellite data are being used to inform decision making and Earth Action?
With multi-decade commercial satellite images provided by NASA CSDA Program, computer- vision algorithms were developed to extract crop fields in smallholder regions in Asia that will be made publicly available. Combined with surveys, agrarian transitions are studied based on characterization of field/farm-size changes in multiple countries that have different land tenure regimes and are at different transition stages.
[1] Hazell and Rahman 2014. New Directions for Smallholder Agriculture. [2] Promkhambut et al. 2023.
World Development, 169, 106309. [3] Lowder et al. 2016.
World development, 87, 16-29. [4] Ricciardi et al. 2021.
Nature Sustainability, 4(7), 651-657.
Project Investigator: Lin Yan, Michigan State University, MI, USA; Email: yanlin@edu.edu
The opinions expressed are solely the PI's and do not reflect NASA's or the US Government's views.