An energy footprint is a measure of land required to absorb the CO2 emissions. This approach focuses on the outcome of energy use, that is CO2 emissions, to highlight the problem and pave the way for corrective action to be taken.
In many regions, environmental problems that are both local (for example, high rates of urbanization, industrial activities, land use changes, or agricultural practices,) and global (for example, desertification, or deforestation) have considerably reduced the ability of land to absorb CO2.
“The total size of the energy footprint in 1999 was 6.72 billion hectares. The earth has about 11.4 billion hectares of biologically productive space [this includes the actually used crop land as well as the additional potential crop land], and the total global ecological footprint in 1999 was 13.65 billion hectares. So energy use comprises about half of humanity’s footprint on the earth … The energy footprint increased from 2.5 billion hectares in 1961 to 6.7 billion in 1999, the fastest-growing component of the overall footprint—and, by the end of the period, very much the biggest.” [Living Planet Report, 2002]