A number of attempts have been made to conceptualize humanity's use of the planet: are we using too much? Calculations based on how much land is needed to produce the food, fuel, housing, transportation, and consumer products for the average American are used to show that it would take five planets to sustainably produce what Americans consume every year. These measurements, codified as the Ecological Footprint (seen above for the entire Earth), are based on the renewable productivity of standardized land uses such as agriculture, forest, and grassland.
Ecological Footprint versus Ecological Health
However, the size of the Ecological Footprint does not take into account most forms of pollution (heavy metals, estrogen mimics, etc) and in general does a poor job of accounting for the differing health of ecosystems. Indeed, according to the Ecological Footprint, non-renewable high-intensity resource use may "use" less land than renewable low-intensity resource use. The problem with this landscape landuse metric is that its focus on "biocapacity" can be at odds with biodiversity and ecosystem health, which the Ecological Footprint does not measure.
Much of this analysis is taken directly from Lenzen, M., C. Borgstrom Hansson and S. Bond (2007) On the bioproductivity and land disturbance metrics of the Ecological Footprint. Ecological Economics 61, 6-10.