Geoscience Reference
In-Depth Information
contamination.in.aquatic.systems.that.have.risen.dramatically.in.modern.times.due.
to. mining,. industrialization,. urban. sprawl,. and. agricultural. processes. (Boone. and.
Bridges.2003)..The.rapid.rate.of.contamination.of.aquatic.systems.can.be.measured.
in.hundreds.of.years,.yet.amphibians.have.been.laying.their.eggs.in.less-contami-
nated.water.for.millions.of.years.
Many.amphibians.still.lay.their.eggs.in.shallow.water,.in.large.communal.masses,.
potentially.subjecting.them.to.exposure.to.both.increasing.UV-B.radiation.and.infec-
tious.diseases..Many.amphibians.school.in.large.numbers.. Newly.metamorphosed.
amphibians. may. form. aggregations.. Amphibian. species. mate. in. large. communal.
groups..These.behaviors.and.ecological.attributes.have.probably.persisted.and.were.
probably.beneicial.for.millions.of.years.(Romer.1939,.1968)..But.under.today's.con-
ditions. these. very. behaviors. may. increase. the. potential. of. acquiring. an. infectious.
disease.. Amphibians. exhibit. such. seemingly. maladaptive. characteristics. because.
evolution.takes.time,.is.not.perfect,.can.only.alter.existing.variations,.and.is.a.com-
promise.of.numerous.selection.pressures.(Blaustein.and.Bancroft.2007)..Those.indi-
viduals.with.the.mechanisms,.behaviors,.and.life-history.attributes.best.able.to.cope.
with.mounting.environmental.changes,.emerging.diseases,.and.the.various.other.fac-
tors.that.amphibians.face.may.produce.offspring.with.those.attributes..Perhaps.these.
adaptations.will.allow.amphibians.to.persist.for.millions.of.years.more.
SUMMARY
Species.loss.is.a.major.part.of.a.“biodiversity.crisis”.that.is.exempliied.by.popula-
tion. declines,. range. reductions,. and. extinctions. of. amphibian. species. around. the.
world.. In. at. least. some. regions,. amphibian. losses. appear. to. be. more. severe. than.
losses. in. other. vertebrate. taxa.. There. appears. to. be. no. single. cause. for. amphib-
ian.population.declines..Like.other.animals,.amphibians.are.affected.by.numerous.
environmental.stresses.that.often.act.in.complex.ways..The.causes.for.the.decline.
of. a. given. species. may. be. different. from. region. to. region. and. even. in. different.
populations. of. the. same. species.. Synergistic. interactions. between. more. than. one.
factor. may. be. involved.. There. may. be. interspeciic. differences. and. even. differ-
ences.between.life.stages.in.how.amphibians.react.to.environmental.changes.and.
other. stresses.. Although. the. major. cause. for. amphibian. population. declines. and.
extinctions.is.probably.habitat.destruction,.climate.change,.diseases,.environmen-
tal.contamination,.and.introduced.exotic.species.may.all.contribute.to.amphibian.
population.declines.
The.emphasis.of.our.review.is.on.climate.change.and.its.relationship.with.other.
factors. such. as. increasing. ultraviolet. radiation. and. disease.. In. this. chapter. we.
address.several.key.questions.concerning.the.effects.of.climate.change.on.amphib-
ians..Are.amphibian.populations.affected.by.global.climate.changes?.What.are.the.
major.climate.changes.affecting.amphibian.populations?.How.are.amphibian.popu-
lations. affected?. The. multifaceted. dynamics. of. climate. change. makes. it. dificult.
to. accurately. predict. the. outcome. of. global. change. on. individual. populations.. A.
multidisciplinary. approach. is. probably. necessary. for. understanding. the. effects. of.
climate. change. on. amphibians.. We. suggest. that. climate. modeling. should. be. forti-
ied.with.laboratory.and.ield.experiments..Experimental.studies.could.be.bolstered.
