HINT:  Clicking on any map on this page will open a higher resolution PDF version, which can then be zoomed, printed, or downloaded. PDF map files posted to this website are designed to reveal excellent detail when zoomed to 400%.

The Invasion Risk Modeling data are now displayed in our new Interactive Map application; both the Invasion Risk Modeling and Remote Sensing Mapping data can also be downloaded HERE



The Yampa River and its associated agricultural water delivery systems are spreading leafy spurge seeds downstream from large areas of infestation that have occupied floodplain areas between Hayden and Craig for several decades. The presence of leafy spurge in these difficult-to-treat riparian environments presents an especially difficult challenge to land managers.


The YRLSP seeks to address this problem through scientific research complementing local knowledge, aimed at the development of effective and sustainable leafy spurge management practices. To this end, the YRLSP developed a relationship with Dr. Dan Tekiela, invasive weed scientist with the Department of Plant Science at the University of Wyoming, who recruited two graduate students—Hannah Kuhns and Chloe Mattilioto work on three leafy spurge research projects in the Yampa River Basin. 

Both Hannah and Chloe have now completed their respective projects. We are happy to report that Hannah successfully defended her thesis in late July 2021, and has received her Master's degree. A copy of her Master's thesis, which also serves as the final report on her project for the YRLSP, can be downloaded HERE.


Hannah also presented a Zoom seminar on a portion of her Master's thesis research, on April 9, 2021. To view the video recording of her very informative presentation click HERE

In the fall of 2021, Chloe completed Chapter 3 of her PhD dissertation—the final comprehensive report on her mapping application projects for the YRLSP. A downloadable PDF of Chapter 3 is available HERE. Chloe's complete dissertation is also now in the final editing stages, and will be available in the spring of 2022 (when it will also be made available for download from the YRLSP website).

If you are looking for a quick overview of Chloe Mattilio's work with leafy spurge mapping, take a look at the update on her the remote-sensing mapping and invasion risk modeling applications that she presented at the August 2021 YRLSP Working Group meeting. A downloadable PDF of her PowerPoint presentation is available HERE.


Integrated Weed Management

Leafy spurge is an extremely difficult species to effectively manage and many standard herbicide management options produce less than satisfactory results. In riparian areas, the problem is more complicated because several of the herbicides used to control leafy spurge in upland areas are not labelled for use near water. Because eradication is nearly impossible for well-established invasions, reducing seed production and the resulting spread of seed to new areas is an important use of management resources to protect the Yampa River corridor, irrigated agricultural lands, and associated uplands.


University of Wyoming graduate student Hannah Kuhns, under the direction of Dr. Tekiela, began working on a project in 2019 to quantify the impacts of sheep grazing, herbicide applications, or a combination of the two on leafy spurge seed production. In 2020 Hannah extended her research to include an examination of the effect of various environmental variables on leafy spurge seed germination rates, as well as the potential for root fragments (such as might be eroded from a river bank during spring floods) to propagate in new downstream environments. Collectively, Hannah's investigations provide new insight into the optimum timing and best management practices for the control of leafy spurge populations in riparian areas.

A leafy spurge root propagule sprouts in Hannah's lab.


Remote Sensing Mapping

University of Wyoming graduate student Chloe Mattilio, under the direction of Dr. Tekiela, has developed a mapping application that will contribute to the control of leafy spurge in the Yampa River Basin. Chloe's remote sensing mapping application detects potential existing leafy spurge infestations using high spatial resolution, multispectral satellite imagery. 


Chloe’s work began in 2019 with searching out appropriate satellite photography (recent, little or no cloud cover, inclusive of our areas of interest in the Yampa River corridor . . . and reasonably priced!). She then applied a number of sophisticated processes to further refine the pixel resolution of the photography, before processing it into multiple spectral band combinations. These were further tweaked by applying different contrast, brightness and gamma values—all in an attempt to tease out the subtle spectral differences recorded in each photographic pixel.


The end goal was to develop an algorithm that can effectively classify each enhanced photographic pixel as to whether it recorded light that was, or was not, reflected from a patch of leafy spurge on the ground. (To see a brief, but more technical description of this stage of Chloe's work, click HERE.)


Chloe's development of the remote-sensing application included correlation with the field mapping data collected by YRLSP in 2019–20. Chloe then conducted further groundtruthing work during the summer of 2021, with the goal of further refining the accuracy of the classification algorithm. The result has been a comprehensive dataset for remotely sensed leafy spurge infestations in the Yampa River corridor.

Unfortunately, the high resolution of this dataset has some practical consequences. It's just too large a set of files to load efficiently into our interactive map as a map layer, so we can only make it available as a downloadable shapefile on our GIS Data page, or displayed in a series of static PDF maps. Below is an example of the remote sensing map series that will soon be available for viewing and downloading from this web page.


An example of remote sensing data displayed in three classes of "confidence" for leafy spurge identification. 


Invasion Risk Modeling

The leafy spurge invasion in the Yampa River Basin is still in progress—what we see today does not define the potential extent of future infestations. Under the direction of Dr. Tekiela, University of Wyoming graduate student Chloe Mattilio has also developed a leafy spurge invasion risk model for Moffat and Routt counties.

A primary resource for this model is the extensive spatial dataset that has been developed in nearby Fremont County, Wyoming. Locations of leafy spurge populations have been recorded by Fremont County Weed & Pest for years, resulting in a robust dataset cataloging over 14,000 individual populations. By correlating environmental data for the Fremont County and Yampa River study area infestations (including soil type, texture, and pH; annual and monthly mean climate temperature and precipitation; location slope, elevation, and aspect; as well as infestation proximity to roads and developed areas), Chloe has built a predictive model for the Yampa River Basin, which will facilitate monitoring potential habitats for the arrival of new leafy spurge infestations in the future.

Using ecological niche model (ENM) algorithms, Chloe created a raster (image) file that predicts habitat suitability for leafy spurge in Moffat and Routt counties, at a resolution of 1km x 1km pixels. Each pixel in the raster represents a unique value along a continuous scale from 0 to 1 (least suitable to most suitable leafy spurge habitat). For ease of display in the YRLSP interactive map application, the original raster pixels were then reclassified into four discrete categories of risk, before conversion to shapefile format.


Invasion risk data for Moffat and Routt counties, displayed in four classes of habitat suitability for potential leafy spurge invasion.