twenty sites needed somehow to represent the entire continent ecologically, so
their selection was critical.
Figure 9: Ecology is rife with uncertainty. For example, any estimate of the number of harbor
seals covered with oil following the Exxon Valdez oil spill is going to be approximate, since you
can’t come close to counting every last one. Even finding a representative sample is hard. New
methods are being developed to separate out sources of uncertainty. Credit: Getty image of seal
and NOAA National Marine Mammal Laboratory for the map.