Real option theory is concerned with the timing of investments that are costly to reverse and where future net benefits are uncertain (risky). Ecologists have determined that geometric Brownian motion is a reasonable model for the population dynamics of an endangered species. In this seminar, the optimal population threshold to initiate a conservation intervention will depend on estimates of the (1) drift and standard deviation rates before and after intervention, (2) fixed and variable costs of the intervention, (3) society's regret should the endangered species go extinct, and (4) society's rate of time preference. The resulting real option model is applied to the captive breeding program for the California condor.