Hi, this is Alex from MinuteEarth. Farmers
are obsessed with water. It makes sense – their livelihoods depend on crops that will die
without enough water. So lots of farmers buy expensive equipment to pump tons of water
to their fields. In fact, of all the water humans use, 70% is for agriculture. But here’s
an even crazier thing – lots of farmers also spend tons of effort and tons of money de-watering
their fields. That’s because too much water is also deadly
for crops. All plant cells need oxygen to function: the cells above the ground take
it from photosynthesis or from the air around, and the cells underground take it from tiny
air pockets in the soil. But if the soil is too wet for too long, the roots can literally
drown, killing the entire plant. Plus, wet fields cause tractors to get stuck and to
compact the soil, which reduces both the amount of air in the soil and the space for roots
to grow. To save their crops from these problems, farmers
around the world have dug ditches and installed special underground pipes to drain excess
water away. As a result, the soil has enough space in it for roots to grow and enough air
for roots to breathe; crops survive, tractors don’t get stuck and overall productivity
increases. However, draining water away more quickly
means that it reaches nearby streams and rivers more quickly, where it can speed up the flow
and contribute to floods. And floods can damage infrastructure and erode river banks and river
bottoms, creating deep channels and muddying the water downstream. Plus, the water coming
from the fields can carry chemicals – from fertilizer and pesticides – which end up polluting
rivers, lakes and eventually, oceans. These problems caused by drainage can be mitigated
somewhat by applying fertilizer and pesticides precisely where and when the crops need them.
We can also send the water through trenches filled with wood chips or buffers of native
plants, both of which can filter out some of the chemicals before the water flows into
a nearby stream. And we can also retrofit the underground pipes to slow down the flow
of water when it’s ok to have a wet field, like when we’re not growing crops. But there is another huge problem with drainage:
it’s helped us turn wetlands into farms. Wetlands are incredibly valuable, because in addition
to providing habitat for fish, birds, and other creatures, they also act like giant
sponges that prevent floods and filter the water – making it cleaner for everyone downstream. In the last 200 years, over half – and maybe
even over ¾ – of the world’s wetlands have disappeared and been replaced mostly with
farmland. So, thanks to drainage we get new and more
productive farmland, which helps us grow lots of extra crops. But we also lose wetlands
and gain some new problems. And unfortunately, gaining the benefits without
any of the downsides may be a pipe dream. This video was sponsored by the University
of Minnesota, where students, faculty and staff across all fields of study are working
to solve the Grand Challenges facing society. One of these challenges is Assuring Clean
Water and Sustainable Ecosystems, and part of the solution is to reduce the pollution
from agricultural runoff. Professor Jacques Finlay and post-doc Christy Dolph in the College
of Biological Sciences, along with collaborators, have found that if we restored wetlands in
strategic locations where they could intercept lots of water, they’d be three times more
effective at removing pollution than wetlands restored elsewhere. Professor Michael Sadowsky
in the Department of Soil, Water, and Climate is identifying the bacteria that remove chemicals
from water sent through woodchip trenches. And Adjunct Professor Heidi Peterson in the
Department of Bioproducts and Biosystems Engineering is collaborating on a project to filter and
retain drainage water using a wetland at the edge of a field. Thanks, University of Minnesota!