Geoscience Reference
In-Depth Information
however,. mountain. chains. are. often. oriented. East-West.. The. Alps,. Pyrenees,. and.
Carpathian. mountain. ranges. are. among. the. East-West-oriented. chains.. For. such.
ranges,.elevational.temperature.gradients.run.parallel.to.latitudinal.gradients..This.
allows. mammals. to. quickly. come. into. equilibrium. with. climatic. changes. as. they.
move.northward.and.upward.into.cooler.climes,.but.potentially.limits.the.possibility.
for.farther.northward.colonizations,.as.such.range.shifts.would.require.animals.to.
move.down.elevation.gradients.into.warmer.valleys.between.the.mountain.ranges.
PART 2: EVIDENCE FOR CONTEMPORARY RANGE
SHIFTS IN RESPONSE TO CLIMATIC CHANGE
We.focus.in.this.chapter.on.the.evidence.for.changing.mammal.distributions.in.the.
very.recent.past.and.present..The.fossil.record.is.essential.for.documenting.mamma-
lian.species.responses.to.climate.changes.over.multiple.time.scales..The.importance.
of.the.fossil.record.cannot.be.overestimated,.but.the.focus.here.is.recent.evidence.
of.response.over.contemporary.time.frames.likely.caused.by.anthropogenic.warm-
ing..Blois.and.Hadly.(2009).provide.an.excellent.summary.of.the.contributions.of.
the.paleontological.record.to.our.understanding.of.mammalian.species.response.to.
climatic.changes.
Contemporary. mammalogists. have. utilized. the. work. of. their. nineteenth-. and.
twentieth-century. predecessors,. new. surveys,. and. climate. records. from. the. recent.
past.and.present.to.gain.a.better.understanding.of.mammal.response.to.recent.climate.
changes.(e.g.,.those.occurring.over.the.past.100.years)..The.typical.climatic.changes.
and.concomitant.mammal.distributional.changes.that.can.occur.over.a.century.may.
seem. trivial. when. compared. to. those. documented. over. much. longer. stretches. of.
time.in.the.paleontological.record..However,.the.last.100.years.on.Earth.have.been.
anything.but.average,.demonstrating.rapid.and.heterogeneous.changes.in.climate.and.
landscape..As.discussed.previously,.it.is.likely.that.the.twenty-irst.century.will.see.
climate.warming.occurring.at.a.faster.rate.than.during.any.previous.time.in.the.past.
65.million.years.
Such.unique.climatic.changes.provide.an.ideal.opportunity.for.studying.the.rela-
tive.importance.of.the.deterministic.factors.for.mammal.response.to.climate.change.
highlighted. previously. in. this. chapter. (e.g.,. species. characteristics,. magnitude. and.
rate.of.climate.change,.topographic.heterogeneity)..Much.of.the.research.up.to.this.
point.has.followed.in.the.natural.progression.of.scientiic.understanding—irst.docu-
menting.the.trends.in.mammalian.distributional.changes,.and.then.developing.more.
in-depth.studies.of.the.potential.drivers.of.these.observed.trends..While.these.latter.
studies. are. under. way,. much. of. our. current. understanding. is. limited. to. inferences.
based.on.correlational.trends.between.distributional.and.climatic.shifts.
Studies.of.modern.mammal.distributional.shifts.due.to.climate.change.generally.
fall. into. one. of. two. categories:. (1). studies. focusing. on. multiple. species. in. a. geo-
graphic.area.smaller.than.the.species'.distributional.range,.or.(2).research.focusing.
on.a.single.species.over.a.broad.geographic.distribution..At.the.heart.of.these.studies.
lies.a.similar.question:.what.determines.the.geographic.range.of.a.species,.and.how.
will.a.change.in.climate.affect.those.range.boundaries?.Studies.that.investigate.range.
