This dataset shows annual tree cover extent,gain, and loss from the year 2001 to 2014, at 30 meter resolution, as colored layers that can be seen together or one at a time as individual layers that can be toggled on and off. Green is used to represent tree cover in 2000, red shows tree cover loss between 2001-2014, blue shows tree cover gain between 2001-2014, and purple is gain and loss together due to replanting after loss has occurred.
“Tree cover” is defined as all vegetation greater than 5 meters in height, and may take the form of natural forests or plantations across a range of canopy densities. “Loss” indicates the removal or mortality of tree cover and can be due to a variety of factors, including mechanical harvesting, fire, disease, or storm damage. As such, “loss” does not directly equate to deforestation.
The dataset is a collaboration between by Global Forest Watch partners at GLAD (Global Land Analysis & Discovery) lab at the University of Maryland, Google, USGS and NASA. The data were generated using Landsat imagery and algorithms to measure where tree cover patterns extend, or are lost, each year. When the algorithm sees the pattern of tree cover is missing or existing after one year, it places a pixel where this occurred. The tree cover extent data is used to measure against the loss or gain, thus giving us a sense of where the trees were to begin with or where they have been planted.
Trees grow much faster in warmer, tropical regions than in colder, boreal regions. That is why there appears to be stronger overlap with loss and gain data (purple) in some parts of the world; trees are cut down, but they might grow back very quickly. This is also true of production forests and plantations; overlap in areas like Scandinavia and the southeast USA look particularly purple because these areas are logged then replanted with more timber trees, or in Indonesia areas are cleared then often replanted with oil palm plantations.
You can view of loss, gain, and extent as separate layers or one on top of each other. When the red loss and the blue gain layer are on top of one another or very close on a pixel-scale level, it looks like purple from afar. For visualizations purposes, we combined these layers into a separate purple layer.
The tree cover loss data is updated annually, but for visualization purposes, this was all aggregated into one layer. Therefore the yearly data from 2001-2014 is all mushed together into one “loss” layer. However, the gain and extent data remain static, as they have only been updated once.