Geoscience Reference
In-Depth Information
during.a.particular.block.of.time.each.year..It.also.is.possible.to.anticipate.a.core.set.
of.species.that.are.likely.to.be.present.during.that.period..Yet,.even.with.real-time.
data. on. weather,. it. can. be. challenging. to. predict. accurately. from. year. to. year. the.
dates. of. irst. and. last. appearance. of. butterlies. of. certain. species,. the. number. of.
individuals.that.will.eclose.and.where,.or.when.an.abundance.of.a.given.species.will.
peak.(Weiss.and.Weiss.1998)..Changes.in.local.butterly.abundances.over.orders.of.
magnitude.are.observed.regularly.in.the.absence.of.obvious.deterministic.environ-
mental.changes,.whether.natural.or.anthropogenic.in.origin..Moreover,.the.degree.
of.synchrony.among.multiple.populations.of.the.same.species.in.a.given.year.often.
cannot.be.forecast.
Whereas.butterlies.may.be.among.the.irst.taxonomic.groups.to.show.the.effects.
of. climate. change,. shifts. in. the. distribution. and. abundance. of. butterlies. are. not.
necessarily.a.direct.relection.of.climate.change..It.may.be.possible.to.explain.much.
of.the.variance.in.a.trend.in.abundance.on.the.basis.of.precipitation..However,.an.
observed.trend.in.abundance.of.a.butterly.species.is.unlikely.to.signal.that.a.speciic.
pattern.of.precipitation.has.occurred..Furthermore,.changes.in.population.dynamics.
of. any. organism. rarely. are. triggered. by. a. change. in. one. environmental. attribute..
Instead,.those.changes.tend.to.relect.suites.of.interacting.or.cascading.changes.in.the.
abiotic.and.biotic.environment..Mechanistic.pathways.by.which.atmospheric.condi-
tions.affect.butterlies.often.involve.larval.host.plants,.sources.of.nectar.for.adults,.
and. rates. of. parasitism. and. disease. rather. than. thresholds. of. physical. tolerance.
(Singer. 1972;. Weiss. et. al.. 1988).. When. human. land. uses. affect. abiotic. and. biotic.
attributes.of.butterly.habitat,.interpreting.the.role.of.weather.and.climate.becomes.
substantively.more.dificult.
Previous.authors,.especially.Dennis.(1993).and.Hellmann.(2002),.have.explained.
in.detail.the.physiological.responses.of.butterlies.to.weather.and.climate..Here,.we.
review.recent.evidence.that.butterlies.are.responding.to.climate.change..We.reex-
amine.previous.projections.of.changes.in.light.of.improved.understanding.of.mecha-
nisms..We.also.provide.guidance.on.future.efforts.to.track.responses.of.butterlies.
to.climate.change..Our.discussion.focuses.on.butterlies.in.temperate.regions..Long-
term.data.on.tropical.butterlies.are.comparatively.rare,.and.the.composition,.let.alone.
the.dynamics,.of.many.tropical.butterly.faunas.are.comparatively.poorly.known.
EVIDENCE OF DIRECTIONAL RESPONSES
OF BUTTERFLIES TO CLIMATE
The. recent.literature. provides. evidence. that. climate. change. is. affecting. butterlies.
via. their. phenologies,. the. location. and. size. of. their. geographic. ranges,. and. their.
abundances.. Most. published. evidence. for. virtually. all. taxonomic. groups. focuses.
on. apparent. responses. (it. is. generally. unknown. whether. responses. are. direct. or.
indirect). of. population. dynamics. to. temperature,. for. which. records. generally. are.
more.complete.than.for.precipitation.(see.Parmesan.et.al..1999;.Thomas.et.al..2001)..
Much.of.the.evidence.is.derived.from.long-established.monitoring.programs.in.the.
United.Kingdom..Data.and.inferences.from.these.monitoring.programs.largely.are.
responsible.for.the.conventional.wisdom.that.measures.of.butterly.occurrence.and.
