Geoscience Reference
In-Depth Information
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The. irst. major. step. toward. a. mechanistic. understanding. of. how. climate. change.
affects.mammalian.range.shifts.is.to.properly.study.these.two.processes.simultane-
ously..Today's.scientiic.community.is.well.equipped.to.take.such.a.step..In.the.past,.
the.climatic.portion.of.this.research.has.been.limited.by.the.location.and.reliability.of.
weather.stations..Stations.accepted.as.components.of.the.Historical.Climate.Network.
(http://cdiac.ornl.gov/epubs/ndp/ushcn/ushcn.html).provide.greater.conidence.in.the.
reliability.of.weather.data,.but.these.weather.stations.do.not.cover.the.landscape.to.
the.degree.needed.to.fully.understand.climatic.links.with.mammalian.range.shifts..
Modern.technology.and.modeling.techniques.are.closing.these.gaps.
Discontinuities. in. weather. data. can. be. managed. via. extrapolation. or. interpola-
tion.through.modeling.(e.g.,.the.PRISM.project,.http://www.prism.oregonstate.edu/),.
the. deployment. of. automated. data. loggers,. or. a. combination. of. these. techniques..
Although.strict.extrapolation.is.a.cost-effective.and.valid.option,.any.modeling.pro-
cedure. without. proper. ground-truthing. can. be. problematic.. Many. mammals. are.
dependent. on. microclimates. that. occur. at. too. ine. a. scale. to. be. detected. or. prop-
erly.modeled.by.these.techniques..Deploying.data.loggers.to.measure.local.climate.
increases. the. reliability. and. sensitivity. of. climatic. measurements;. however,. the.
increased.cost.and.labor.associated.with.this.technique.limits.its.applicability..The.
third.of.these.options,.combining.information.from.data.loggers.and.weather.stations.
to.model.climatic.patterns,.may.be.the.best.option..This.technique.essentially.pro-
vides.the.ground-truthing.needed.to.improve.extrapolation.models,.while.not.requir-
ing.full.coverage.of.the.landscape.in.data.loggers..As.demonstrated.in.Beever.et.al..
2010,.these.techniques.can.also.be.used.to.increase.the.temporal.extent.as.well.as.the.
spatial.resolution.of.historical.climate.data.
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In.order.to.take.full.advantage.of.improved.climatic.data,.we.must.monitor.popula-
tions.with.equal.thoroughness..As.we.argue.below,.Long.Term.Ecological.Research.
(LTER). sites. are. essential. but. not. suficient. to. carry. out. monitoring. of. mammal.
responses.to.climatic.changes..While.LTER.sites.are.increasing.in.number.and.many.
have.compiled.mammal.population.data.for.several.decades,.the.temporal.depth.and.
spatial. extent. of. these. datasets. varies. among. sites.. Generally,. range. edges. do. not.
coincide.with.LTER.sites..Thus,.further.monitoring.at.appropriate.range.boundaries.
should.be.initiated.to.properly.document.range.shifts..Due.to.the.cyclical.nature.of.
many.(particularly.small).mammal.population.dynamics,.demographic.monitoring.
must.be.consistent.and.long.term..In.addition,.to.truly.understand.range-shift.dynam-
ics.and.correctly.diagnose.range.contractions.and.expansions,.monitoring.across.the.
full.geographic.range.of.focal.species.is.critical..Such.range-wide.monitoring.will.
require.careful.selection.of.key.populations.and.habitats..In.the.best-case.scenario,.
the.number.and.distribution.of.sites.surveyed.will.be.adequate.to.support.statistical.
analyses. intended. to. determine. the. relative. importance. of. hypothesized. site. occu-
pancy.covariates.
