Jamieson on Natives versus Exotics

pp. 175-180


1.       Virtually all environmentalist prefer native to exotic species

2.       How characterize natives/exotics?

3.       One definition: A species exotic to an environment if would not be there w/o human action (e.g., European rats that tagged along on voyages of discovery)

          a.       Problem: Counts some species as exotic, when clearly native

                    i.        Species humanly-introduced but then evolves into a new species–is native as evolved here and is endemic (found now where else)

                              (1)     Salt cedar introduced as ornamental plant and now all over desert Southwest

                    ii.       Species restored by humans can be native (Yellowstone Wolves), but would not be there w/o human action

          b.       Problem: Counts some species as native, which are clearly exotic

                    i.        When finches first made it to Galapagos Islands 10,000 years ago, got there on own but clearly exotic


4.       Second definition: Species exotic when occurs outside of its historical range

          a.       Handles cases of rats, salt-cedar, and finches

          b.       Problem: How far back in time do we go to assess species historical range?

                    i.        Before 13,000 years ago were camels, elephants and cheetahs in North America

                    ii.       If we introduced their African cousins, would that count as native species reclaiming historical range?

          c.       Problem: Historical range can shift

                    i.        Once were palm trees in Canada, but if planted one there now, it would be exotic

5.       Third definition: Species exotic if not well integrated into ecological community

          a.       Problems

                    i.        Lots of exotic organisms have no demonstrable impact on ecosystems

                    ii.       Some native species go wild and “unbalance” ecosystem (are not well integrated)

                              (1)     Asian-Long-Horned Beetle damages trees in Chicago and in native range


          b.       Exotic species can naturalize over time


6.       Jamieson thinks “exotic species” is a value laden term and we must balance those values against others

7.       So in many cases eliminating exotics may be worse than tolerating them

          a.       Worried about saving nature by exotics elimination as a “war against the unwanted”

Questions for Jamieson on Natives vs. Exotics

8.       Describe at least two definitions of exotic species and give examples that those definitions have trouble accounting for.

9.       Does Jamieson think it an important environmental goal to eliminate all exotic species? Do you?