Land Cover Map - Yukon-Charley Rivers National Preseve

The land cover of Yukon-Charley Rivers National Preserve is a complex mosaic of forests, shrublands, barren areas, and water, as shown in this view of the Charley River region.

A land cover map shows where different kinds of vegetation are located. In Yukon-Charley Rivers National Preserve these are mostly different kinds of forests, like "Upland Spruce Forest," and shrublands, like "Alpine Low Shrub." The map also displays different kinds of unvegetated areas, such as water bodies, gravel bars along rivers, and high-altitude rocky areas. Land cover maps help us understand not only the abundance and distribution of plants in the preserve, but also the wildlife that depends on the plants. They are also help us understand and predict the behavior of wildfires and evaluate off-trail travel routes. Scientists use land cover maps to understand and predict the distribution of soils and permafrost.

Why we update land cover maps

Yukon-Charley Rivers National Preserve has an older land-cover map that was made in the 1990s. About one-fifth of the preserve has burned in wildfires since that map was made, so the existing vegetation was mostly destroyed and is growing back. Another one-fifth of the preserve burned in the decades prior to the 1990s map, and vegetation has changed as the vegetation grew back. In addition, the vegetation and gravel bars along the Yukon River are in a constant state of change as islands and gravel bars grow and are eroded. Plus trees and shrubs at high elevations in the mountains have expanded uphill due to climate warming. Also, the tools and resources available to make a land cover map have improved a lot since the 1990s: now we have many more and better satellite images, from both the summer and fall seasons, new data on topography and vegetation height, over 2,000 vegetation plots that have been sampled on the ground, and improved computer-assisted techniques for mapmaking.

How the map was made

The basic geographic layers used to make the map are:

1. satellite images from the summer and fall seasons, mostly from the years 2021 and 2022. These were taken by the Sentinel-2 satellite, which has 10-meter (33-foot) pixels and registers visible and infra-red colors;
2. topographic information (elevation, slope steepness and curvature, and exposure to the south) from a digital elevation model; and
3. vegetation height, from airborne radar.

The original images were smoothed to remove unwanted noisy detail. We also hand-delineated some areas that we know have different land cover types, such as riparian areas (river floodplains) and alpine areas with limestone rock. Then we used existing vegetation plots and visual interpretation of the images to locate 2,800 training points, which are examples of known land cover. We then used a computer classification technique modified from the k-nearest neighbor method to classify unknown areas by matching them to the most similar known training points.

The land cover map (right) was made from Sentinel-2 satellite images taken in the summer (left) and fall (center), plus other map layers with information about vegetation height and topography.

How to use the new map

The new map is available as a GIS (geographic information systems) layer that can be downloaded from the NPS Data Store (see link below). A report that describes in detail how the map was made can also be downloaded from that link. The map is designed to be used at a scale of about 1:24,000, and the smallest features visible on it are about 0.5 ha (1 acre) in size. The map displays 38 land cover types, including 31 vegetation types, water bodies, and 6 different kinds of barren or sparsely vegetated areas. Options for aggregating the 38 types are suggested for users who don't need this much detail.

Get the map and report

Yukon-Charley Rivers National Preserve Land Cover Map