An article by leading US scientists and co-authored by the JRC finds that forests are becoming increasingly fragmented, resulting in a higher level of global forest degradation and ecological risks than had previously been estimated.
The authors looked specifically at where and how forest loss occurs, as interior forest loss is much more damaging to the maintenance of ecological services than losing forest at the boundary. Such ecological services, which are vital to environmental and human health, include carbon storage, nutrient cycling, water and air purification, the maintenance of wildlife habitat, and the prevention of erosion.
The authors analysed changes in tree cover maps using Landsat satellite imagery from 2000 and 2012 at the global level as well as for 768 ecological regions. They found a net loss of global forest area of 3.2% (1.71 million km2). In addition to forest loss it is important to analyse forest fragmentation, which is a significant driver of forest degradation and habitat loss. Mapping changes in forest interior area, the authors found that the elasticity (rate of loss of forest interior compared to the rate of loss of all forest area) was 3.1 times higher on the global scale, with a net loss of 9.9% (3.76 million km2) of interior forest areas between 2000 and 2012. While most (38%) global interior forest loss occurred in the Tropical and Subtropical Moist Broadleaf Forests biome, the highest rates of loss were found in the Temperate Coniferous Forest, the Mediterranean Forests, Woodlands and Scrub, and the Tropical and Subtropical Dry Broadleaf Forests biomes. The percentage of forests within 700 m of the edge, and therefore subject to degrading effects of fragmentation, was found to have increased from 62% in 2000 to 77% in 2012.
Forest fragmentation is an important environmental driver. Monitoring sudden changes in forest interior can provide an early warning of impending ‘tipping points’ in dependent ecological functions, allowing for targeted interventions or guiding where further detailed investigations may be needed. Mapping tree cover using remote sensing is the best means currently available for consistently mapping and monitoring the global status and trends of forest interior area. The European Space Agency’s Sentinel-2 mission will provide the continuous high-resolution imagery required to detect and analyse future changes on the global and regional scales.