Geoscience Reference
In-Depth Information
track.the.distribution.of.suitable.climates.more.readily.by.colonizing.natural.habitats.
in.mountains.rather.than.by.moving.across.lowlands.dominated.by.intensive.human.
land.use,.where.the.distributions.of.many.species.are.failing.to.keep.up.with.climate.
change.(Warren.et.al..2001;.Menéndez.et.al..2006).
Indeed,.some.of.the.irst.and.most.widely.cited.examples.of.ecological.responses.to.
climate.change.refer.to.elevational.changes.in.species.distributions..Parmesan.(1996,.
2005). showed. that. the. average. elevation. of. populations. of. the. butterly.
Euphydryas
editha
.in.western.North.America.shifted.upward.by.124.m.during.the.twentieth.cen-
tury.(the.average.latitude.also.shifted.north.by.92.km),.as.isotherms.shifted.uphill.by.
105.m..Pounds.et.al..(1999).recorded.increasing.domination.of.the.bird.and.herptile.
fauna.of.Monteverde.National.Park.in.Costa.Rica.by.species.associated.with.lower.ele-
vations,.consistent.with.increasingly.dry.local.conditions.between.the.1980s.and.1998..
Grabherr.et.al..(1994).found.that.plant.species.richness.had.increased.on.mountain-
tops.in.the.Alps,.with.estimated.rates.of.elevational.expansion.of.<1-4.m.per.decade,.
compared.with.8-10.m.decadal.upward.shifts.in.isotherms..In.another.example.where.
plant.distributions.did.not.appear.to.be.keeping.pace.with.climate.change,.Wardle.and.
Coleman. (1992). recorded. uphill. shifts. in. the. treeline. of. 5-30. m. during. the. twenti-
eth.century.in.New.Zealand..Meta-analysis.revealed.an.average.observed.uphill.shift.
in. distributions. of. 6.1. m. per. decade. (Parmesan. and. Yohe. 2003),. consistent. with. an.
effect.of.climate.warming,.but.likely.not.keeping.pace.with.rates.of.climate.change.
(the.twentieth.century.increase.in.terrestrial.surface.temperature.of.0.6-0.7°C.would.
represent. an. upward. shift. in. isotherms. of.
c.
10. m. per. decade,. for. a. 6°C/km. lapse.
rate)..Lapse.rates.in.the.tropics,.especially.humid.locations,.are.lower,.which.would.
translate.to.higher.range.shifts.to.compensate.for.changes.in.temperature.(Colwell.et.
al..2008;.Sekercioglu.et.al..2008)..In.a.review.of.ecological.responses.to.recent.climate.
change,.Parmesan.(2006).noted.that.uphill.range.shifts.had.been.rather.poorly.docu-
mented.compared.with.latitudinal.shifts..The.majority.of.documented.range.shifts.also.
referred.to.poleward.or.uphill.
expansions
,.rather.than.to.range.
contractions
.at.trailing.
edges.(Parmesan.and.Yohe.2003;.Rosenzweig.et.al..2007).
Why. so. few. early. examples. reported. either. elevation. range. shifts. or. lower. lat-
itude/elevation. contractions. appears. to. relect. partly. the. fact. that. few. researchers.
were. looking. for. them,. and. partly. that. the. data. used. were. unable. to. detect. these.
kinds.of.change.(Parmesan.2006;.Thomas.et.al..2006)..Two.general.approaches.have.
been.used.to.gather.evidence.for.elevational.shifts..Atlas.distribution.data.have.been.
compared.between.different.time.periods,.and.elevational.gradients.with.prior.infor-
mation.on.species.distributions.have.been.resampled.systematically..Both.types.of.
comparison.present.challenges.in.ensuring.that.changes.to.sampling.effort.or.regime.
do.not.bias.results.(see.the.following;.see.also.Rowe.2005.for.museum.specimens,.
Bergamini.et.al..2009.for.herbarium.specimens,.and.Tingley.and.Beissinger.2009.for.
a.review)..One.problem.particularly.with.atlas.data.is.that.one.presence.in.a.new.grid.
square.or.region,.or.on.a.new.mountain.summit,.is.suficient.to.detect.a.range.expan-
sion,.whereas.contracting.species.may.decline.gradually.to.patchy.refugia.(Wilson.et.
al..2004),.so.that.it.is.dificult.to.document.unequivocally.the.extinction.of.a.species.
from.a.region..As.a.result,.few.such.declines.could.be.documented.using.coarse-scale.
atlas.data..In.fact,.elevation.range.shifts.may.have.helped.to.obscure.range.contrac-
tions.at.species'.lower.latitudinal.margins,.if.species.shifted.their.distributions.uphill.
