Geoscience Reference
In-Depth Information
the.spatial.responses.of.1350.species.of.plants.across.Europe.by.using.an.ensemble.of.
seven.future.scenarios..They.found.that.a.large.but.variable.proportion.of.pixels.(up.
to.42%.across.the.continent).could.potentially.lose.species,.and.that.more.than.half.
of.the.species.could.become.vulnerable.or.threatened.by.2080,.mainly.those.inhabit-
ing.mountains..In.an.analogous.investigation.that.modeled.species.responses.across.
an.area.covering.about.20%.of.the.Earth's.surface,.a.contentious.meta-analysis.esti-
mated.that.15-37%.of.species.will.be.“committed.to.extinction”.by.2050.(Thomas.
et.al..2004).
On.the.other.hand,.the.simplicity.and.versatility.of.this.analytical.tool.frequently.
drives. users. to. misuse. or.abuse. it.when. no. clear.understanding. of. its. assumptions.
and. capabilities. exists.. In. effect,. this. converts. what. should. be. testing. of. scientiic.
hypotheses.into.mere.menial.tasks..Below,.I.present.the.main.conceptual.and.techni-
cal.limitations.and.associated.uncertainties.of.ENMs.when.they.are.used.for.predict-
ing.species.distributions.through.time;.I.also.offer.advances.to.overcome,.or.at.least.
evaluate,.these.limitations..One.such.limitation.in.anticipating.the.effects.of.climate.
change.on.the.geographic.distribution.of.species.relates.to.species'.intrinsic.dispersal.
ability.(Best.et.al..2007)..Equilibrium.with.climate.at.the.present.time.indicates.that.
dispersal.capability.of.a.species.has.been.suficient.to.occupy.the.available.suitable.
habitat;.however,.this.does.not.ensure.that.it.will.be.able.to.keep.pace.with.climate.
change,.which.(at.least.for.temperature).has.been.more.rapid.than.it.has.been.during.
the.last.tens.of.millennia,.across.most.of.the.world.(Rahmstorf.et.al..2007;.Randall.
et.al..2007)..In.fact,.ability.to.keep.pace.would.seem.to.not.be.the.norm..There.is.a.
variable.amount.of.lag.between.the.onset.of.suitable.climatic.conditions.and.the.time.
of.arrival.of.new.immigrants.(or.populations),.and.also.between.the.time.when.con-
ditions.shift.from.suitable.to.unsuitable.and.when.local.population.extinctions.occur,.
and.these.two.lags.are.asymmetrical.(Devictor.et.al..2008).
These.“leading-edge”.and.“trailing-edge”.dynamics.have.started.to.be.incorpo-
rated.in.modeling.exercises.to.better.understand.and.represent.distributional.shifts.
(Thomas. et. al.. 2001;. Thuiller. et. al.. 2008).. For. example,. Anderson. et. al.. (2009).
coupled. a. niche. model. with. a. dynamic. metapopulation. model. into. which. disper-
sal.information.was.incorporated.to.analyze.the.dynamics.of.range.margins.of.two.
lagomorphs.at.risk.of.extinction.(
Romerolagus diazi
.and.
Lepus timidus
)..Under.this.
approach,.the.authors.were.able.to.detect.differences.in.migration.rates.between.the.
leading.and.trailing.edges,.providing.insights.into.the.processes.behind.changes.in.
distributional. patterns. and. thus. improving. upon. performance. of. traditional,. static.
ENMs..In.another.study,.Thuiller.et.al..(2008).present.some.alternatives.for.includ-
ing.ancillary.information.into.ENMs.in.order.to.produce.projections.for.the.future.
that. are. more. realistic,. in. the. face. of. climate. change.. They. propose. incorporating.
ield. data. on. migration. rates,. as. well. as. demographic. information,. into. ENMs. to.
capture.leading-.and.trailing-edge.dynamics.
A. second. line. of. research. for. improving. ENMs. involves. integration. of. biotic.
interactions.into.the.modeling.process..Evidence.is.mounting.that.interspeciic.inter-
actions.have.a.signiicant.effect.on.the.distribution.of.species.not.only.at.the.local.
scale,.but.also.at.the.macroecological.scale.(Araújo.and.Luoto.2007;.Gotelli.et.al..
2010)..Some.forms.of.interactions.are.quite.clearly.determinants.of.species'.distri-
butions,. such. as. (1). parasite. species. that. depend. on. hosts. and. vectors. to. complete.
