Mapping tree cover is vital for monitoring deforestation, restoration and trends in global land cover change. Remote sensing makes it possible to observe forests on a global scale by analyzing imagery from satellites to detect where trees are and aren’t over time. It’s not just dense forests that are important; open canopy forests — which are common in drylands and in non-forested regions like in cities and on farms — are also important to map and monitor. However, doing so has proven challenging: Patches of trees may cover a smaller area than individual satellite pixels. This means trees in open canopy forests are often excluded by lower-resolution data sets, resulting in an inaccurate inventory of tree cover.
Global Forest Watch (GFW) is home to three remote sensing tree cover data sets widely used for quantifying forest trends and creating timely snapshots of the state of global tree extent. Two of these data sets — the University of Maryland GLAD Lab’s Tree Canopy Cover and Tree Cover Height — have 30-meter resolution and are derived from Landsat satellite imagery. These data sets are widely used for many applications, and they have the benefit of Landsat’s long historical archive to provide a consistent understanding of global tree cover trends over recent decades. However, one limitation of these data sets is that their resolution of 30 meters is usually not granular (high resolution) enough to map open canopy forests or small disturbances in closed canopy forests. But a newly updated data set available on GFW, Tropical Tree Cover (TTC), uses higher-resolution data to map trees inside and outside of dense forests. Using 10-meter global imagery from Sentinel-2 satellites launched in 2015, the TTC data set maps tree cover across the tropics with greater granularity, improving our ability to quantify tree cover on non-forest lands, such as urban areas and cropland, and monitor trees at small spatial scales. TTC was originally launched on GFW in 2021 and is now updated to expand from non-forest land use to total coverage of the tropics in high resolution. The updated TTC data set is now fully available to download and analyze on GFW.
