Willow Creek Preserve – The Butterfly Effect

Developement is the biggest threat to what’s left of this northwest prairie, home to imperiled  plant  species  like  Bradshaw’s  lomatium,  the  Willamette  daisy,  and  Kincaid’s lupine. The Fender’s blue butterfly, once considered extinct, is dependent on lupines for survival. Off-road activities disturb or destroy natural habitats, and introduced species threaten to choke out rare native plants. Until 1989, entomologists had crossed the Fender’s blue butterfly off their lists. As far as  they  could  tell,  it  was  gone.  Kaput. Finito. Extinct.

And then they found them again, in this surviving  sliver  of  native  wet  prairie  on former   farmland   remarkably   close   to downtown  Eugene,  Oregon.  Not  surprisingly,  the  butterflies  were  found  close  to where the rare Kincaid’s blue lupine grows. That  makes  perfect  sense;  the  Kincaid’s blue  lupine  is  the  only  place  where  the Fender’s  blue  will  lay  its  eggs.  Its  larvae remain there, feeding on the bright purple flower  spikes,  for  nearly  a  year.  In  late spring, the larvae hatch into adults, beautiful dark-blue butterflies about an inch long. As adults, they will feed on a wider variety of  wildflowers.  But  that  only  lasts  for  9 days  before  they  lay  their  eggs—on  the lupine, of course—and then die. The new larvae  snuggle  into  the  lupines,  and  the whole cycle begins again.

That’s  what  happens  when  you  preserve  the  old-time  habitats.  Spreading over  508  acres  (206  hectares),  Willow Creek Preserve is an intact remnant of the upland grasslands, ash woods, and perennial streams that used to cover this Northwest river valley. It’s estimated that 99.8% of  the  native  wet  prairie  has  been  lost  to development  since  the  1940s.  But  here along Willow Creek, more than 200 native plant,  100  bird,  and  25  butterfly  species survive  in  healthy  diversity.  In  late  spring you’ll  find  the  starlike  yellow  clusters  of the   endangered   Bradshaw’s   lomatium, while  tall  feathery  blue  camas  perfectly complement  snug  yellow  buttercups  as they grow side by side in an open meadow. In midsummer, the endangered Willamette Valley  daisy  arrives,  with  its  fat  yellow center and pinkish ray petals. Lacy Oregon white-topped  asters  come  along  at  the end of the summer.

In  adjacent  areas,  trees  and  shrubs have taken over the native prairie; at Willow  Creek,  periodic  burning  holds  them back, as nature intended, and lets the sunloving flowers maintain their territory. (Bradshaw’s lomatium, in fact, has increased by 50% in the areas where fire has been used to  manage  growth.)  Non-native  species like  Scotch  broom  and  Himalayan  blackberry  that  have  driven  out  the  original species  are  regularly  cleared  out.  Where the waist-high, fine-leaved tufted hairgrass should  dominate,  volunteers  tear  out  the tough  common  teasel,  an  invasive  thistle that’s  trying  to  take  over.  Sure,  it  takes  a lot of work—but one glimpse of a Fender’s blue butterfly makes it all worthwhile.