Geoscience Reference
In-Depth Information
.
2..
Upper limits of species distributions.
. Atlas. data. suggest. increases. in. the.
upper.elevations.occupied.by.butterly.species.(Hill.et.al..2002;.Konvicka.
et.al..2003),.although.analyses.using.the.average.elevations.of.≥10.km.grid.
squares. are. likely. to. underestimate. uphill. expansions. because. of. topo-
graphic.variation.within.grid.cells..Other.multispecies.evidence.for.upslope.
extensions.by.invertebrates.is.not.forthcoming.(Table 6.1)..In.contrast,.there.
is.abundant.information.that.plant.species.are.extending.their.distributions.
to.higher.elevations,.predominantly.from.studies.on.the.lora.of.European.
mountain.summits.(references.in.Table 6.1),.from.boundaries.between.dom-
inant.vegetation.communities.in.Europe.and.North.America.(Pẽuelas.and.
Boada.2003;.Beckage.et.al..2008).and.from.the.extension.of.tree.lines.in.
temperate.and.polar.mountain.ranges.(Kullman.2001,.2002;.Moiseev.and.
Shiyatov.2003;.for.a.comprehensive.review.see.Harsch.et.al..2009)..Repeat.
surveys. of. herptile. distributions. along. elevation. gradients. in. the. Tropics.
show.increases.in.upper.range.limits.for.some.species.over.the.last.10-40.
years.(Bustamante.et.al..2005;.Raxworthy.et.al..2008)..In.Peru,.three.anuran.
species.colonized.elevations.of.5244-5400.m.(the.highest.known.amphib-
ian.populations.in.the.world).following.recent.glacial.retreat.(Seimon.et.al..
2007)..Repeat.surveys.of.a.3000-m.elevation.gradient.in.California.showed.
that.four.species.of.small.mammal.had.extended.their.upper.limits.to.higher.
elevations,. but. a. further. three. species. showed. signiicant. contractions. at.
upper.range.margins.(Moritz.et.al..2008)..Reported.upper.elevation.limits.
for.Southeast.Asian.birds.based.on.historical.(pre-1971).and.recent.(1971-
1999).data.suggest.that.84.out.of.306.species.have.shifted.their.distributions.
upward,.by.an.average.of.399.m.(Peh.2007).
.
. Approximately. twice. as. many. published. studies. provide. estimates. for.
decadal.rates.of.change.in.upper.limits.of.species'.ranges.than.for.average.
or. lower. elevations. (Figure 6.1).. Reported. decadal. expansion. rates. range.
from. 1. to. 4. m. (Grabherr. et. al.. 1994;. Pẽuelas. and. Boada. 2003). to.
c.
50.
m. (Kullman. 2002;. Battisti. et. al.. 2005),. with.the. majority. in. the. range. of.
10-30.m.per.decade.(e.g.,.Klanderud.and.Birks.2003;.Walther.et.al..2005;.
Beckage.et.al..2008;.Parolo.and.Rossi.2008;.Raxworthy.et.al..2008)..There.
is.a.suggestion.that.analyses.based.on.more.recent.resurveys.of.alpine.lora.
indicate.faster.rates.of.change.(Walther.et.al..2005;.Pauli.et.al..2007),.which.
might. be. expected. based. on. increased. rates. of. warming. since. the. 1970s.
(Rosenzweig.et.al..2007)..Increasing.rates.of.uphill.expansion.are.not.clear.
from.published.data.on.all.taxonomic.groups.(Figure 6.1b),.but.are.likely.
obscured. by. differences. in. data. quality. and. the. ecological. characteristics.
of.different.systems..Nevertheless,.the.studies.showing.the.fastest.rates.of.
uphill.expansion.have.demonstrated.the.importance.of.very.recent.condi-
tions.for.observed.range.shifts..For.example,.Kullman.(2002).showed.that.
in.2000,.saplings.above.the.former.elevation.range.of.seven.tree.and.shrub.
species.in.the.Swedish.Scandes.were.aged.between.7.and.12.years,.corre-
sponding.to.strong.winter.and.summer.warming.since.1988.
.
3..
Lower limits of species distributions.
.If.climate.change.causes.low-elevation.
range.margins.to.shift.upward,.then.the.outcome.is.a.reduction.in.species'.
