Fig. 1. The full set of possible futures of ecosystem services (blue ellipse) is only partially represented in available data (green circle) and models (magenta circle). Together, the data and the models allow us to project the uncertainties, or knowable unknowns (yellow ellipse). The unknowable unknowns are the portion of the blue ellipse beyond the edge of the yellow ellipse. The probability of any model projection of future ecosystem services depends on the full set of possible futures, most of which are unknown. This diagram is based on the ideas of L. A. Smith (2002).