Satellites can give us a wealth of data about the world, but until recently, this data gave us only the very big picture.
Working with remote sensing data, scientists have now developed a way to look at the change in species across a landscape, transforming their ability to analyze the spread of invasive species.
Cheatgrass is a Hardy Invasive
The focus of their study was cheatgrass, an invasive species that that “cheats” cattle of nutrients.
Jennifer Balch of Penn State’s Department of Geography has studied the grass, which likely arrived in the United States with settlers who are thought to have brought it in contaminated wheat. Cheatgrass germinates in the fall and grows early in the spring, getting a jump on the surrounding plants. Its large root systems allow it to draw moisture from a larger area than other grasses, while its abundant seeds make it a super producer.
Cheatgrass is well-placed to be a successful invader, and it easily forms mats between the plants in native sagebrush and saltbrush ecosystems.
Native Ecosystems and Human Developments
The current extent of the cheatgrass invasion is massive: over 15,000 square miles, or 100 times the size of Salt Lake City. The grass has invaded the salt brush and sagebrush ecosystems that are indigenous to the Great Basin. It’s a natural firestarter, and its presence increases the frequency of fires in an area. While the native plants in the Great Basin are adapted to fire, they’re not used to experiencing it at such a high frequency.
Due to its propensity to catch on fire, cheatgrass poses a danger to some animals that rely on native ecosystems, such as the sage grouse. It’s also dangerous to people: in areas where housing developments rub shoulders with native ecosystems; the invasion of cheatgrass can cause fires near human infrastructure.
Observing Invasive Species via Remote Sensing
While it was already possible to observe the spread of cheatgrass by looking at local ecosystems across Nevada, California, Oregon, and Utah, the satellite photos brought this analysis to a landscape scale. Using techniques developed by her colleague Bethany Bradley, Balch was able to detect cheatgrass on remotely-sensed images, which opened up a new way to monitor the extent of species. The study analyzed twenty years of remote sensing data, deepening knowledge of the spread of the grass. Balch told Decoded Science that grassland managers had observed an increase in fire in areas dominated by cheatgrass, but studying the satellite photos revealed just how closely-linked fire and cheatgrass really are.
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