What Landsat sees in North Dakota

North Dakota spent most of its history as an economic afterthought — food,
hunting, fishing, wide-open space. The Bakken changed that, and it changed the
landscape with it: oil and gas pads spreading across the prairie, thousands of
new residents in Williston and Watford City.

At the same time, and for unrelated reasons, the depressional wetlands of the
Prairie Pothole Region on the eastern side of the state have been growing.

Both changes are visible from orbit, because the Landsat archive is fifty
years of the same ground photographed the same way.

Energy, at 30 metres

The obvious use of a fifty-year archive is the before-and-after picture. The
more useful one is the National Land Cover Database, which sorts every
30-metre plot in the United States into a land-cover class — wetland,
cultivated crop, and so on — and re-releases nationally every two or three
years, with extra layers for things like impervious urban surface.

That turns "the Bakken has changed the landscape" into a number you can put a
date on.

Crops

Agriculture brought in more than $7.3 billion in 2020 — with processing,
7.6% of the state's GDP — and the crop list is unusually broad. In 2020 North
Dakota led the nation in **all dry edible beans, pinto beans, canola,
flaxseed, honey, rye, all sunflower and all wheat.**

Landsat is a key input to the USDA's Cropland Data Layer, which maps crop type
year by year across the lower 48. But the satellite sees more than the eye
does, and that is where the rest of the value is: infrared and near-infrared
bands make crop health measurable at scale, and the thermal sensors give
evapotranspiration — evaporation from the ground plus transpiration through
leaves, which is how much water a crop is actually using.

Wetlands that will not hold still

North Dakota's wetlands are critical habitat for migratory birds — the Prairie
Pothole Region across Minnesota, the Dakotas and Canada is breeding ground for
more than half of North America's migratory birds — and they change
constantly. Some shrink as seasonal wetlands are drained for crops. Others
grow.

High-resolution aerial survey maps them beautifully and costs too much to
repeat often. Landsat is coarser and it comes back. That lets researchers map
extent year by year, watch the trend within a single year, tell an ephemeral
lake from a permanent one, and model what happens next.

*The same prairie potholes in Stutsman County, dry and wet. The satellite
images were taken on 2 September 1992 and 23 May in a wet year.*

Sources

Written from the U.S. Geological Survey Fact Sheet North Dakota and Landsat,
a work of the United States government in the public domain. Wetland methods
from Rover and others (2011) and Vanderhoof and others (2017); migratory bird
figure from the U.S. Environmental Protection Agency (2021).