Bringing Space Age Technology to the Beartooth Plateau
Our project will use snow tracking and scat analysis, two of the oldest, simplest, and most effective techniques devised for learning more about animals like river otters. But how can we learn more about their environment, especially when it covers such a vast area like the Beartooth Plateau? And how can we understand what that environment was like in past decades, and how it has changed in recent years, both of which are necessary to know how and why these otters started moving there? Fortunately, there is a treasure trove of climate and landscape data collected and archived by U.S. government research agencies, available to all scientists in places like USGS EarthExplorer. These include Landsat satellite imagery, which will be especially important for this project.
The Landsat mission began in 1972 with the launching of Landsat 1. As technology improves and sensors become more sensitive--and as old equipment wears out and batteries run out of juice--additional satellites are launched: Landsat 8 took orbit in 2013, while Landsat 9 is slated to launch in 2020. As a result, we have 45-years worth of continuous Earth observation, monitoring an especially dynamic time for its people and ecosystems. Launching and running these satellites isn't cheap--Landsat 8 cost $450 million to build, while the operation cost is expected to push $1 billion by the end of next year--but the data they provide has been considered a stunning return on public investment: they've been critical for drought monitoring, agricultural analyses, disaster response, tools like Google Earth, and research like this otter project!
But the continuity of this priceless dataset almost failed when, in October 1993, the rocket carrying Landsat 6 didn't have enough oomph to propel the satellite into orbit, causing it to burn up as it fell back into the earth's atmosphere. That placed the burden of continuing the mission on Landsat 5's metallic shoulders. Designed to last 10 years, Landsat 5 carried on for nearly 30 years, earning a place in the Guinness World Records as the longest operating earth observation satellite (I didn't realize that was even a category!) as well as the esteem of scientists around the world. Let's all take a moment to thank that little (4,800-pound) satellite and the engineers who designed it for their invaluable contribution to science.
Yet the imagery alone, like any raw data, is not useful until it has been processed, analyzed, and applied. Here, for example, is an infrared image of the Beartooth Plateau taken by Landsat 5 on June 6, 2006:
Can you see all the open water and snow in this image? Can you tell how thick the lake ice is? These are important environmental parameters we need to know for our otter habitat suitability analysis, and this image alone doesn't provide them. But now, check out this image:
These might not be the colors you were expecting, but now we can clearly see the open water (black) and the snow (yellow), and we can also get some idea about ice (orange) conditions too. That's because this is a combination of the infrared, near infrared, and red wavelength bands, collected by Landsat 5 and assembled using geographic information systems (GIS). Properly interpreted, "false color images" like this reveal landscape details like those we need for the otter analysis. And thanks to the 45-year history of the Landsat mission (including the critical gap filled by Landsat 5 between 1993 and 2011), we can also observe and compare changes over time, like this:
Here we can clearly see that the previous decade had more snow and ice, while the following decade had less snow and ice. But why aren't we comparing the same dates for each decade? That's because the satellite is orbiting the Earth while the Earth rotates on its own axis, so the satellite can only pass the same spot every 16 days. And sometimes, 16 days later, that spot is covered in clouds that block the imagery. Those are limitations to the Landsat dataset, but they are a small price to pay for the valuable information it provides.
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