The Secret Global Sewer System

Thanks to the University of Minnesota for sponsoring this video!

Ditches and drain pipes help crops survive but can negatively impact the broader landscape.

Thanks also to our Patreon patrons and our YouTube members.
To learn more, start your googling with these keywords:
Waterlog – to saturate (a field) with water; a problem for most crops
Drainage – the removal of liquid (water) from an area
Ditch – a narrow channel dug in the ground, typically used for drainage alongside a road or the edge of a field
Drain tile – a pipe buried (beneath a field) for drainage. Originally made of ceramic tiles, now typically of corrugated plastic
Precision agriculture – putting corn seed + small dose of fertilizer/pesticides in hole in ground
Controlled drainage – the use of a water control structure to raise the depth of a drain tile outlet to hold water in the field when drainage isn’t needed
Wood chip bioreactor – an underground trench filled with wood chips that provide carbon for bacteria that denitrify the water flowing through it
Saturated buffer – a strip on the edge of a field filled with plants & bacteria that can remove some nitrogen from the water flowing onto it from drain tiles
Denitrification – the removal of nitrogen from a substance (soil, air, or water) by chemical reduction, typically via bacteria
Wetland – an area of land where water covers the soil year-round or at certain times of year
Ecosystem services – the free benefits humans get from natural ecosystems
If you liked this week’s video, you might also like:
Why plant roots need oxygen:
Restored wetlands don’t recover their original ecosystem functions:
A guide to agricultural drainage:
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Credits (and Twitter handles):
Script Writer, Script Editor and Video Narrator: Alex Reich (@alexhreich)
Video Illustrator and Director: Ever Salazar (@eversalazar)
With Contributions From: Henry Reich, Kate Yoshida, Peter Reich, David Goldenberg, Julián Gómez, Sarah Berman, Arcadi Garcia Rius
Music by: Nathaniel Schroeder:

Image Credits: Aerial view of treatment wetlands – Photo by David Hansen



Christianson, L.E. & Helmers, M.J., 2011. Woodchip Bioreactors for Nitrate in Agricultural Drainage. Agriculture and Environment Extension Publications. 85.

Davidson, N. C. 2014. How much wetland has the world lost? Long-term and recent trends in global wetland area. Marine and Freshwater Research, 65(10), 934-941.

Davidson, N. C., Fluet-Chouinard, E., & Finlayson, C. M. 2018. Global extent and distribution of wetlands: trends and issues. Marine and Freshwater Research, 69(4), 620-627.

Discovery Farms MN. November 2016. Controlling Nutrient Loss in Tile Systems.

Dolph, C. Pers. comm. June 2019

Erb, K. H., et al. 2017. Land management: data availability and process understanding for global change studies. Global change biology, 23(2), 512-533.

Feick, S., Siebert, S., & Döll, P. 2005. A digital global map of artificially drained agricultural areas.

Finlay, J. Pers. comm. June 2019

Foufoula‐Georgiou, E., et al. 2015. The change of nature and the nature of change in agricultural landscapes: Hydrologic regime shifts modulate ecological transitions. Water Resources Research, 51(8), 6649-6671.

Hansen, A. T., Dolph, C. L., Foufoula-Georgiou, E., & Finlay, J. C. 2018. Contribution of wetlands to nitrate removal at the watershed scale. Nature Geoscience, 11(2), 127.

IPBES. 2019. Summary for policymakers of the global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. S. Díaz, et al. (eds.). IPBES secretariat, Bonn, Germany. Pg 11-12.

Millennium Ecosystem Assessment. 2005. Ecosystems and human well-being: Wetlands and Water Synthesis. World Resources Institute, Washington, DC.

Mustroph, A. 2018. Improving flooding tolerance of crop plants. Agronomy, 8(9), 160.

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