After the last ice age began, the number of plant species in South America changed rapidly. The relationship between the elapsed time, $t$, in years, since the ice age began, and the total number of plant species, $P(t)$, is modeled by the following function: ###$P(t)=30{,}000{,}000\cdot \left(\dfrac{8}{9}\right)\^{\Large t}$ **Complete the following sentence about the yearly rate of change of the number of plant species.** Every year, the number of plant species [[☃ dropdown 2]] by a factor of [[☃ math-keypad 1]].