See the label for Figure 1. I’m not sure why army1987 retracted his comment, but he is correct: the y-axis is logarithmic for the survivorship curve. So the graph actually confirms your expectation and shows an exponential decrease in population.
(Unfortunately, the graph label in the National Geographic article is just wrong—there is no reasonable interpretation under which the logarithmic survivorship curve can be interpreted as a raw proportion.)
On the last panel (that for hypericum) of the figure on the NatGeo page the red curve doesn’t look like the negative derivative of the gray curve, so I assumed I was missing something.
Full paper: Jones et al. (2013)
See the label for Figure 1. I’m not sure why army1987 retracted his comment, but he is correct: the y-axis is logarithmic for the survivorship curve. So the graph actually confirms your expectation and shows an exponential decrease in population.
(Unfortunately, the graph label in the National Geographic article is just wrong—there is no reasonable interpretation under which the logarithmic survivorship curve can be interpreted as a raw proportion.)
On the last panel (that for hypericum) of the figure on the NatGeo page the red curve doesn’t look like the negative derivative of the gray curve, so I assumed I was missing something.