Just south of The Hague, in the Westland region of the Netherlands, acresupon acres of greenhouses are spread across the landscape. They’ve been built by Dutch farmers as part of a 20-year movement by the country to pursue sustainable agriculture by growing indoors.

Dutch farmer H. Zwinkel grows tomatoes in two greenhouses that cover 20 acres of land. His annual harvest of two-and-a-half million pounds of tomatoes is more than double the average yield of an outdoor farm.

Growers like him achieve high yields by controlling the climate and water for their crops under glass: filtration systems allow them to collect and recycle the plants’ water supply. Crops receive direct sunlight supplemented by artificial light, and are protected from unpredictable weather events and insects, and this almost completely eliminates the use of chemical pesticides.

These growing techniques have helped foster an indoor growing boom in the Netherlands: greenhouses now produce 35 percent of the country’s vegetables–despite occupying less than one percent of its farmland.

The Netherlands’ Wageningen University has led much of the research on how to best grow crops indoors. L. Marceli, professor at the university, says that in the era of climate change the Dutch agricultural revolution needs to move beyond greenhouses, which still rely on some outside forces like sunlight. He is now experimenting with indoor vertical farming: growing plants stacked on shelves to maximize space, completely cut-off from the outside. As in many greenhouses, water for the plants is drained, collected, and reused, reducing their dependence on an outside water source, and instead of sunlight, the researchers use LEDs: light bulbs that can replicate solar light in a variety of colors and intensities.

One important part of their work is developing techniques that can be replicated anywhere, even in arid climates like the Middle East or sub-Saharan Africa. The United Nations estimates that global food demand will rise 70 percent by 2050, even as the amount of water and farmable land shrinks due to the global warming.

The Netherlands is already doing its part to feed the world: propelled by indoor farming, it’s become the second biggest food exporter in the world.