More than 1.3m hectares of the planet under glass or plastic
Mapped Copenhagen Sources Algorithms Cropping Modern Years Satellite The Used In Land Fold About Using Of Imagery, It Of And For Four Increased Of 40 Said University Amount And Worldwide, Has Researchers Protected
Growing in glass houses or in open fields wrapped in plastic films covers at least 1.3 million hectares of the Earth's surface, nearly three times more than previous estimates.
Using algorithms and modern sources of satellite imagery, University of Copenhagen researchers mapped the amount of land used for protected cropping worldwide, and said it has increased about four-fold in 40 years.
The new figure of 3.2m acres is the equivalent of nearly 30% of Ireland's used agricultural land.
The new research revealed that the largest growth occurred in China, now home to 60% of the world’s protected cropping. The largest cluster in China, and the world, covers more than 82,000 hectares near Weifang city in northeastern China. In this part of China, fruits and vegetables are generally grown, and high-value fruits such as strawberries, grapes, kiwi, and dragon fruit, are increasing.
Greenhouses, whether under polyethylene film, polycarbonate, or glass, are an effective and relatively inexpensive way to increase yields, by extending the growing season, with control over temperature and lighting, using innovations such as drip irrigation, artificial soil, and hydroponics.
It is estimated greenhouse expansion helped Chinese growers increase production of tomatoes, cucumbers, and gherkins sixfold from 1990 to 2020.
The other clusters in four countries with the most greenhouse area are Almería, Spain; Bari, Italy; Antalya, Turkey; and Chapala, Mexico.
The researchers mapped greenhouses in 119 countries, including Spain (5.6% of the global total greenhouse area), Italy (4.1%), Mexico (3.3%), Turkey (2.4%), Morocco (2.3%), South Korea (1.8%), Japan (1.7%), the Netherlands (1.4%) and France (1.3%). They also mapped greenhouses in 22 countries in Africa, where they are primarily used for vegetable and cut flower production.
Earlier assessments of the global extent of greenhouses were based on industry reports. The researchers now say 1.3m hectares is a conservative estimate, because seasonal production with a duration of less than a year is not included.
Researcher Xiaoye Tong linked the glasshouse boom in China to its strong economic performance, the rise of an urban population with purchasing power, and government subsidies and support for farmers. Similar support for greenhouses in arid and semi-arid regions of the world have boosted local food security and alleviated poverty.
But report co-author Marianne Nylandsted Larsen said very little is known of the environmental and social consequences of greenhouse cultivation in the Global South, which can include over-exploitation of water resources, high energy consumption, contamination of groundwater, soil degradation, plastic pollution, and poor working conditions. The researchers said regulation in greenhouse cultivation needs to be addressed.
