Ecological Deficit is the level of resource consumption and waste discharge by a population in excess of locally sustainable natural production and assimilative capacity. In spatial terms, the ecological deficit is the difference between that population's effective ecological footprint and the geographic area it actually occupies. It basically promotes overall resource efficiency to reduce our Footprint.
"The difference between the biocapacity and Ecological Footprint of a region or country. An ecological deficit occurs when the Footprint of a population exceeds the biocapacity of the area available to that population. Conversely, an ecological reserve exists when the biocapacity of a region exceeds its population's Footprint. If there is a regional or national ecological deficit, it means that the region is either importing biocapacity through trade or liquidating regional ecological assets. In contrast, the global ecological deficit cannot be compensated through trade, and is therefore equal to overshoot."