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remote sensing satellite penguin

Penguins and other strange things we study from space

How scientists use satellites to answer questions about life here on planet Earth.

Thoughts of penguin research may bring to mind Antarctic research vessels and scientists layered in puffy down coats. However, in 2012, researchers Peter Fretwell and colleagues figured out a new way to study penguin populations… from space [1].

image alt text Fig. 1 Typical emperor penguin (not as seen from space). (Source: Christopher Michel Flickr License CC By 2.0)

Using satellite images, scientists confirmed seven new Emperor Penguin colonies on the Antarctic coastline by finding their guano (another word for poo). Although guano typically appears dark against a stark white background, it can be difficult to distinguish from snow or shadows. To be sure of their detection methods, scientists ground truthed their observations, meaning they actually visited suspected penguin sites to make sure their interpretations of satellite images were correct. This ended in good news for penguin lovers as it nearly doubled the estimate of Emperor Penguins in Antarctica.

image alt text Fig. 2 Typical emperor penguin guano (as seen from space). (Source: Modified from Fretwell et al., 2012.)

If we can study penguins, you may be wondering what else is visible from space. A hostile grass takeover? Desert dust? The Great Wall of China?

In the 1800s, long before we introduced satellites into Earth’s orbit, we introduced cheatgrass (Bromus tectorum) into the western US. Since then, cheatgrass has aggressively invaded native ecosystems destroying native grassland and shrubland species. But don’t most grasses look alike? Surely we can’t identify a grass species in a satellite photo taken from over 400 miles away. It is true that we couldn’t… until we learned how we could. In 2005 researchers Bradley and Mustard figured out how cheatgrass’ response to rain would set it apart from other Great Basin species in the western US [2]. Native species in the western US are used to dry climates. In particularly rainy years, these native species are not able to take advantage of the extra water, and so their growth rates remain similar. Cheatgrass however is able use the extra water for very productive growing seasons. By examining the changes in satellite images between years in vegetation cover, Bradley and Mustard created large scale accurate maps of the current cheatgrass distribution.

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Fig. 3 Areas in the Great Basin invaded by cheatgrass show an extremely positive response to high rainfall totals (red and blue). This map was created using information from satellite images. (Source: Modified from Bradley and Mustard, 2005).

So far we have covered penguins and grass. But can we see anything smaller?

From space, the ocean is a beautiful blue color. However it can be distorted by dust particles and other aerosols in that atmosphere. For years, scientists corrected these distortions and used the resulting images to study the ocean and its properties. But in 2006, researchers Antoine and Nobileau used the color distortions to find information about the problem particles themselves. By deciphering the meaning behind ocean color inconsistencies in satellite images, Antoine and Nobileau provided further evidence that dust from the Saharan Desert was blowing over the Mediterranean Ocean at an increasing rate [3]. These dust particles can impact marine life, and even affect rain acidity .

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Fig. 4 Aerial image of Epares archipelago, Indian Ocean. (Source: NASA)

That leaves us with the Great Wall of China. While tough to see, parts of it are indeed visible from space. Though the use of satellite images in science, called remote sensing, has become increasingly popular, you don’t need to worry about satellites snapping a picture of you poolside because they can’t take detailed pictures of small individual things. However, scientists have found that we can get a better idea of what is happening here on Earth by taking a few BIG steps back.

References

[1] Fretwell, Peter T., Michelle A. LaRue, Paul Morin, Gerald L. Kooyman, Barbara Wienecke, Norman Ratcliffe, Adrian J. Fox, Andrew H. Fleming, Claire Porter, and Phil N. Trathan. “An emperor penguin population estimate: the first global, synoptic survey of a species from space.” PLoS One 7, no. 4 (2012): e33751.

[2] Bradley, Bethany A., and John F. Mustard. “Identifying land cover variability distinct from land cover change: cheatgrass in the Great Basin.” Remote Sensing of Environment 94, no. 2 (2005): 204-213.

[3] Antoine, David, and D. Nobileau. “Recent increase of Saharan dust transport over the Mediterranean Sea, as revealed from ocean color satellite (SeaWiFS) observations.”  Journal of Geophysical Research: Atmospheres 111, no. D12 (2006).

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