Geoscience Reference
In-Depth Information
than.animals.from.control.groups..Measures.of.immune.response.showed.a.decrease.
with. increasing. severity. of. the. desiccation. treatment.. It. was. unclear. whether. the.
observed.depression.in.immune.response.was.transient.or.permanent..However,.even.
temporary.periods.of.immune.system.suppression.shortly.after.metamorphosis.could.
lead.to.greater.susceptibility.to.pathogens.
AMBIENT UV-B RADIATION IS HARMFUL TO AMPHIBIANS
AND MAY INTERACT WITH CLIMATE CHANGE
Increases.in.UV-B.radiation.due.to.ozone.depletion.and.other.dynamics.have.been.
documented. in. both. temperate. and. tropical. ecosystems.. However,. even. relatively.
steady. ambient. levels. of. UV-B. radiation. can. harm. amphibians,. especially. if. there.
are.synergistic.effects.with.other.agents,.such.as.contaminants,.pathogens,.or.other.
stressors.. UV-B. radiation. interacts. with. other. stressors. to. affect. a. wide. array. of.
organisms.and.entire.ecological.communities.(Tevini.1993;.van.der.Leun.et.al..1998;.
Cockell.and.Blaustein.2001;.Bancroft.et.al..2007).
Spectral. measurements. made. at. Toronto,. Canada,. since. 1989. indicate. a. 35%.
annual.increase.in.UV-B.radiation.per.year.in.winter.and.a.7%.increase.in.summer.
(Kerr. and. McElroy. 1993).. These. increases. were. caused. by. a. downward. trend. in.
ozone. that. was. measured. at. Toronto. during. the. same. time.. Moreover,. it. was. sug-
gested.that.increases.in.UV-B.in.late.spring.might.have.a.disproportionately.larger.
effect.on.some.amphibian.species.if.the.increases.occur.at.critical.phases.of.amphib-
ian.development.(Kerr.and.McElroy.1993)..This.supports.the.results.of.studies.show-
ing.the.adverse.effects.of.UV-B.radiation.in.spring-conducted.ield.experiments.on.
developing.amphibian.embryos.(discussed.below).
Middleton.et.al..(2001).assessed.trends.in.solar.UV-B.radiation.over.20.sites.in.
Central.and.South.America,.derived.from.the.Total.Ozone.Mapping.Spectrometer.
satellite.data..They.showed.that.annually.averaged.UV-B.doses,.as.well.as.the.maxi-
mum. values,. have. been. increasing. in. both. regions. since. 1979.. The. UV. index. was.
consistently.higher.for.Central.America,.where.many.amphibian.declines.have.been.
documented.(Lips.1998;.Pounds.et.al..1999)..They.conclude.that.further.investiga-
tion.of.the.role.of.UV-B.radiation.in.amphibian.declines.is.warranted.
Using.satellite.data,.Middleton.et.al..(2001).attempted.to.examine.a.potential.rela-
tionship.among.amphibian.declines.in.Central.and.South.America.and.trends.in.solar.
radiation.where.declines.occurred..The.data.collected.by.Middleton.et.al..(2001).was.
consistent. with. experimental. evidence. that. UV-B. radiation. is. harmful. to. amphib-
ians.and.that.increasing.UV-B.levels.may.be.contributing.to.amphibian.population.
declines.(Bancroft.et.al..2008a;.Blaustein.et.al..1998,.2001a)..However,.as.discussed.
in.detail.by.Middleton.et.al..(2001),.data.gathered.from.remote.sensing.have.many.
limitations.. For. example,. there. are. few. long-term. data. sets. on. amphibian. popula-
tions.to.serve.as.a.baseline.data.source.for.remote.sensing.(Blaustein.et.al..1994c)..
Moreover,.there.are.a.number.of.shortcomings.when.using.data.generated.from.satel-
lites,.including.the.fact.that.resolution.of.the.satellite-generated.data.is.not.accurate.
enough.to.approximate.ground-level.interpretations.(Middleton.et.al..2001).
