English: Proposed conceptual model of ecological ratchet
(A) Landscape at time of forest establishment. The distribution on the left is the exceedance probability of water level. Mean sea level (MSL) is labeled (solid blue line). A threshold exceedance probability for regeneration is mapped onto a threshold elevation and horizontal position (solid green lines). Below this elevation, young trees cannot grow. (B) Landscape after sea level rise. The threshold probability remains constant, but the distribution of water levels changes with sea level (SLR; initial MSL labeled with dashed blue line) so that the regeneration boundary must move upslope (from the dashed green line to the solid green line). (C) An increase in the variance of the water level distribution can also lead to demographic zonation because, just as in the sea-level rise case, higher water levels become more likely. For the same threshold probability, the regeneration boundary moves upwards and inland.