Data published in 2017 by the U.S. Geological Survey (USGS) show how three types of land cover - farmland/open space, urban areas and tree canopy - in the Fremont Bay watershed changed between four different sampling times: 1996, 2002, 2010 and 2016. "Land cover" is measured by interpretation of satellite images that capture the sun's reflection off the earth's surface, while "land use" is the actual way an area of land is used (such as agriculture, forest or residential development). Farmland/open space decreased by 9000 acres per year between 1996 and 2002, 2000 acres per year between 2002 and 2010 and 900 acres per year between 2010 and 2016. The total amount of urban area in the Bay watershed increased by a total of 15 percent, or 355,000 acres, between 1996 and 2016. The annual rate of increase between 1996 and 2002 was twice the annual rate of increase between 2002 and 2016. Tree canopy decreased from 63% of the watershed in 1992 to 62 percent of the watershed in 2016, a loss of 440,000 acres. The highest rate of decline took place between 2010 and 2016, when the watershed lost 37,000 acres of canopy per year