Geoscience Reference
In-Depth Information
climate. impacts. and. develop. hypotheses. for. further. study. in. more. complex. land-
scapes..Their.work.clearly.demonstrated.that.mammals.are.shifting.their.elevational.
ranges.in.this.region,.and.climate.change.is.the.most.probable.cause.of.these.shifts..
They.also.highlight.the.importance.of.life.history.traits.and.species'.tolerances.in.
predicting.mammal.reaction.to.climate.change..The.range.contraction.and.upward.
shifts.seen.in.this.study.support.the.predictions.summarized.in.Table 5.1.
Although.the.Yosemite.resurvey.focused.on.elevational.shifts,.multispecies.stud-
ies. from. the. northern. Great. Lakes. region. of. the. United. States. have. documented.
rapid.shifts.in.latitudinal.range.boundaries.(Myers.et.al..2009;.Jannett.et.al..2007)..
The.northern.Great.Lakes.region.is.an.ideal.location.for.studying.such.shifts,.as.it.
represents. a. transition. between. mammal. assemblages. commonly. associated. with.
southern.versus.northern.North.American.habitats..Myers.et.al..(2009).focused.their.
study.on.nine.common.mammal.species.reaching.either.their.southern.or.northern.
limit.in.the.area..Using.museum.and.other.collection.records.from.1883.to.1980.and.
museum.and.ield.survey.results.since.1980,.the.authors.documented.distributional.
shifts.for.these.species..As.predicted,.species.whose.northern.boundary.falls.in.this.
region.are.experiencing.northward.range.boundary.expansion..Over.the.last.15.years,.
species.such.as.the.white-footed.mouse.(
Peromyscus leucopus
).and.southern.lying.
squirrel.(
Glaucomys volans
).extended.their.northern.range.edge.by.as.much.as.225.
km.(15.km/year).based.on.available.sampling..Although.differential.sampling.effort.
can. lead. to. biased. estimates. of. movement. rates. (Shoo. et. al.. 2006),. these. rates. of.
range.expansion.would.be.fast.at.half.the.estimated.speed..Also.as.predicted,.species.
for.which.the.northern.Great.Lakes.region.represents.a.southern.geographic.bound-
ary.are.experiencing.contraction.of.this.southern.range.edge.and.are.being.replaced.
in. community. assemblages. by. southern. species.. These. distributional. changes. cor-
respond. to. increases. in. temperature. in. the. region. of. 2.1°C. for. daily. minima. and.
0.46°C.for.daily.maxima.since.1970,.though.local.trends.were.highly.heterogeneous..
Although. additional. factors. could. affect. these. species'. distributions,. the. authors.
argue. that. the. overwhelming. unidirectional. nature. of. mammal. distribution. shifts,.
despite.heterogeneity.in.forest.management.regimes.and.human.land-use.patterns,.
indicate.a.single.dominant.causal.factor—climate.change.
The.work.of.Myers.et.al..(2009).and.Moritz.et.al..(2008).shows.an.obvious.change.
in. mammal. community. compositions. and. range. limits. in. northern. Michigan. and.
Yosemite.National.Park..These.studies.clearly.demonstrate.that.species.at.temper-
ate.latitudes.and.in.mountainous.areas.are.responsive.to.climatic.changes;.what.is.
less. clear. is. whether. any. of. the. species. used. in. these. studies. are. showing. overall.
range.collapses..In.the.following.section,.we.highlight.studies.on.single.species.over.
larger.spatial.scales,.focusing.on.single.species.that.have.suspected.vulnerabilities.
to. climatic. changes.. These. studies. more. directly. address. questions. about. overall.
distributional.changes.
Single Species in a Broad Geographic Area
Species.with.narrow.physiological.tolerances,.such.as.those.in.alpine.and.arctic.habi-
tats,.are.frequently.the.focus.of.single-species.studies.due.to.their.predicted.vulner-
ability.to.changes.in.climate..In.addition,.two.factors.pertaining.to.arctic.and.alpine.
species. allow. us. to. more. easily. isolate. climatic. drivers. as. causal. mechanisms. for.
