Since the release of Cuesta Roble Consulting's 2018 World Greenhouse Vegetable Statistics publication, several questions have been asked regarding the types of structures used in “greenhouse” versus “protected agriculture” statistics. The answers are related to the actual definitions used.
For greenhouse vegetable production, the most commonly used definition is: “only permanent structures covered with glass or plastic, and generally excluding simple high or low tunnels, shade houses, etc.” Other definitions add to the permanent structure requirement “with climate controls” and “with computerized irrigation systems.”
The definition of protected agricultural production includes “mulches, row covers, shade structures, greenhouses, etc. Any type of method or structure used to extend the growing season of plants."
Using these definitions, estimates of the global production area for both “greenhouse” and “protected agriculture” have been made, using government statistical references as available, updated to January 2018.
Global Greenhouse Vegetable Area: 497,815 hectares (1,230,128 acres)
Global Protected Agriculture Vegetable Area: 3,414,353 hectares (8,437,050 acres)
In some references, China alone is said to have 3 million hectares (8 million acres) of “greenhouse vegetables.” However, less than 2 percent of this total is in climate-controlled greenhouses. Other references show 8,847 ha. of “heated greenhouses” in China. Based on a detailed report from The Netherlands for one province in China, the breakdown of “protected cultivation” structures for greenhouse vegetable production has been calculated. According to this report: China: Tianjin Province: Total- 20,000 ha. “Greenhouse” – 4133 ha. “Tunnels”- 15867 ha.