The Howland Cooperating Experimental Forest is located ~60 km north of Bangor, Maine in a low elevation ommercial spruce fir forest ecosystem. Research at the site initially focused on nutrient cycling and soil ecology studies. In 1996 measurements of forest carbon uptake and loss (carbon sequestration studies) were begun as part of the AmeriFlux program, and Howland now has one of the longest records of carbon flux measurement in the world.
Howland is an important land validation site for NASA, first serving as a field site for the Forest Ecosystem Dynamics project and now operating as a core EOS and MODIS validation site as well as part of AERONET (aerosol optical depth network). It is also a test site for ongoing remote sensing studies of tree biomass and soil moisture, and its above-canopy webcam records daily images as part of the PHENOCAM phenology network, and the site records soil moisture as part of the COSMOS program.