  Survival probability within a certain time horizon T is a common measure of
population viability. The choice of T implicitly involves a time preference,
similar to economic discounting: Conservation success is evaluated at the time
horizon T, while all effects that occur later than T are not considered.
Despite the obvious relevance of the time horizon, ecological studies seldom
analyze its impact on the evaluation of conservation options. In this paper, we
show that, while the choice of T does not change the ranking of conservation
options for single species under stationary conditions, it may substantially
change conservation decisions for multiple species. We conclude that it is of
crucial importance to investigate the sensitivity of model results to the
choice of the time horizon or other measures of time preference when
prioritizing biodiversity conservation efforts.
