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distribution. sizes. (Wilson. et. al.. 2005). and. an. increase. in. extinction. risk.
(Williams.et.al..2003;.Sekercioglu.et.al..2008)..Despite.the.urgency.of.iden-
tifying.whether.such.changes.are.occurring,.far.fewer.studies.have.reported.
uphill.contractions.at.downslope.margins.than.expansions.at.upslope.limits..
Part.of.the.reason.for.this.discrepancy.is.that.the.studies.that.have.identiied.
uphill. advances. (e.g.,. tree-line. elevations,. alpine. summit. lora). may. be.
unlikely.to.detect.species.at.their.low-elevation.limits,.although.vegetation.
studies.have.noted.declines.in.abundance.of.high-altitude.species.at.lower.
elevation.sites.(Klanderud.and.Birks.2003;.Pẽuelas.and.Boada.2003;.Pauli.
et.al..2007;.Kelly.and.Goulden.2008).
.
. For.plants,.observed.low-elevation.limits.may.shift.upward.slowly.where.
long-lived. individuals. survive. but. fail. to. reproduce. (Pẽuelas. and. Boada.
2003;.Pauli.et.al..2007)..For.short-lived.ectothermic.animals,.low.elevation.
range.limits.may.shift.uphill.rapidly,.associated.with.increasing.tempera-
tures..Four.British.butterly.species.and.ten.Czech.butterly.species.showed.
extinctions. from. low. elevation. atlas. grid. squares. between. the. 1970s. and.
1990s. (Hill. et. al.. 2002;. Konvicka. et. al.. 2003).. In. central. Spain,. the. low-
elevation. limits. of. 16. butterly. species. shifted. uphill. on. average. by. 212.
m. between. 1967-1973. and. 2004,. as. annual. mean. temperature. increased.
by.1.3°C.(equivalent.to.a.
c.
225-m.rise.in.isotherms).(Wilson.et.al..2005)..
Thirty.montane.herptile.species.in.Madagascar.showed.an.average.increase.
in.low-elevation.limit.of.76.m.(59.m.when.correcting.data.for.changes.to.
sampling.effort).between.1993.and.2003,.although.the.majority.of.species.
showed.no.change.or.a.slight.decrease.in.sampled.lower.limit.(Raxworthy.
et.al..2008).
.
. Endotherms. also. show. some. evidence. for. uphill. shifts. in. lower. range.
limits..Of.28.small.mammal.species.whose.elevation.ranges.were.sampled.
in.Yosemite.National.Park.in.1914-1920.and.2003-2006,.ten.showed.sig-
niicant.increases.in.lower.limits.(mean.+499.m),.while.two.showed.signii-
cant.decreases.(mean.-744.m).(Moritz.et.al..2008)..However,.only.ten.out.of.
306.generalist.bird.species.in.Southeast.Asia.showed.apparent.uphill.shifts.
in. low-elevation. limits. between. two. published. ield. guides. (Peh. 2007)..
Reported.range.expansions.by.bird.species.at.both.high-.and.low-elevation.
limits.in.Europe.appear.to.represent.responses.of.overall.population.size.to.
increased. habitat. favorability. across. the. elevation. range. (Archaux. 2004),.
possibly.related.to.climate.conditions.in.one.case.(Tryjanowski.et.al..2005)..
Shifts.in.low-elevation.limits.are.in.the.range.of.25-81.m.per.decade.where.
reported. (apart. from. one. study. using. atlas. data:. +14. m. per. decade;. Hill.
et.al..2002),.tallying.well.with.isotherm.shifts.of.approximately.30-70.m.
per.decade.since.the.1960s.(Figure 6.1c)..However,.data.for.decadal.rates.
should.be.treated.with.some.caution,.as.neither.climatic.change.nor.biotic.
responses.are.likely.to.be.gradual.in.nature..For.example,.ieldwork.for.two.
recent.European.studies.showing.uphill.shifts.in.butterly.distributions.was.
conducted.in.2004.and.2005.(Wilson.et.al..2005;.Franco.et.al..2006),.fol-
lowing.the.hot.summer.of.2003..Some.species.probably.suffered.increased.
rates.of.low.elevation.extinctions.in.2003,.rather.than.declining.gradually.
