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11 Are sheep going blind in Chile?




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This article is from the Ozone Depletion: UV Radiation and its Effects FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.

11 Are sheep going blind in Chile?

If they are, it's not because of ozone depletion.

For a short period each year, the edge of the ozone hole passes
over Tierra del Fuego, at the southern end of the South American
continent. This has led to a flurry of reports of medical damage
to humans and livestock. Dermatologists claim that they are seeing
more patients with sun-related conditions, nursery owners report
damage to plants, a sailor says that his yacht's dacron sails have
become brittle, and a rancher declares that 50 of his sheep,
grazing at high altitudes, suffer "temporary cataracts" in the
spring. (_Newsweek_, 9 December 1991, p. 43; NY Times, 27 July
1991, p. C4; 27 March 1992, p. A7).

These claims are hard to believe. At such a high latitude,
springtime UV-B is naturally very low and the temporary increase
due to ozone depletion still results in a UV fluence that is well
below that found at lower latitudes. Moreover, the climate of
Patagonia is notoriously cold and wet. (There is actually more of
a problem in the summer, after the hole breaks up and ozone-poor
air drifts north. The ozone depletion is smaller, but the
background UV intensity is much higher.) There may well be effects
on _local_ species, adapted to low UV levels, but even these are
not expected to appear so soon. It was only in 1987 that the hole
grew large enough to give rise to significant UV increases
in southern Chile, and cataracts and malignant melanomas take many
years to develop. To be sure, people do get sunburns and
skin cancer even in Alaska and northern Europe, and all
else being equal one expects on purely statistical grounds such
cases to increase, from a small number to a slightly larger number.
All else is definitely not equal, however - the residents are now
intensely aware of the hazards of UV radiation and are likely to
protect themselves better. I suspect that the increase in
sun-related skin problems noted by the dermatologists comes about
because more people are taking such cases to their doctors.

As for the blind sheep, a group at Johns Hopkins has investigated
this and ascribes it to a local infection ("pink eye"). [Pearce]

This is _not_ meant to dismiss UV-B increases in Patagonia as
insignificant. Damage to local plants, for example, may well emerge
in the long term, as the ozone hole is expected to last for 50
years or more. The biological consequences of UV radiation are real,
but often very subtle; I personally find it hard to believe that
such effects are showing up so soon, and in such a dramatic fashion.
Ozone depletion is a real problem, but this particular story is a red
herring.

 

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