The Connection Between Ozone Depletion and UVB Radiation
Reductions in ozone levels will lead to higher levels of UVB
reaching the Earth's surface. The sun's output of UVB does not change;
rather, less ozone means less protection, and hence more UVB reaches
the Earth. Studies have shown that in the Antarctic, the amount
of UVB measured at the surface can double during the annual ozone
hole. Another study confirmed the relationship between reduced ozone
and increased UVB levels in Canada during the past several years.
Effects on Human Health
Laboratory and epidemiological studies demonstrate that UVB causes
nonmelanoma skin cancer and plays a major role in malignant melanoma
development. In addition, UVB has been linked to cataracts. All
sunlight contains some UVB, even with normal ozone levels. It is
always important to limit exposure to the sun. However, ozone depletion
will increase the amount of UVB and the risk of health effects.
Effects on Plants
Physiological and developmental processes of plants are affected
by UVB radiation, even by the amount of UVB in present-day sunlight.
Despite mechanisms to reduce or repair these effects and a limited
ability to adapt to increased levels of UVB, plant growth can be
directly affected by UVB radiation.
Indirect changes caused by UVB (such as changes in plant form,
how nutrients are distributed within the plant, timing of developmental
phases and secondary metabolism) may be equally, or sometimes more,
important than damaging effects of UVB. These changes can have important
implications for plant competitive balance, herbivory, plant diseases,
and biogeochemical cycles.
Effects on Marine Ecosystems
Phytoplankton form the foundation of aquatic food webs. Phytoplankton
productivity is limited to the euphotic zone, the upper layer of
the water column in which there is sufficient sunlight to support
net productivity. The position of the organisms in the euphotic
zone is influenced by the action of wind and waves. In addition,
many phytoplankton are capable of active movements that enhance
their productivity and, therefore, their survival. Exposure to solar
UVB radiation has been shown to affect both orientation mechanisms
and motility in phytoplankton, resulting in reduced survival rates
for these organisms. Scientists have demonstrated a direct reduction
in phytoplankton production due to ozone depletion-related increases
in UVB. One study has indicated a 6-12% reduction in the marginal
ice zone.
Solar UVB radiation has been found to cause damage to early developmental
stages of fish, shrimp, crab, amphibians and other animals. The
most severe effects are decreased reproductive capacity and impaired
larval development. Even at current levels, solar UVB radiation
is a limiting factor, and small increases in UVB exposure could
result in significant reduction in the size of the population of
animals that eat these smaller creatures.
Effects on Biogeochemical Cycles
Increases in solar UV radiation could affect terrestrial and aquatic
biogeochemical cycles, thus altering both sources and sinks of greenhouse
and chemically-important trace gases e.g., carbon dioxide (CO2),
carbon monoxide (CO), carbonyl sulfide (COS) and possibly other
gases, including ozone. These potential changes would contribute
to biosphere-atmosphere feedbacks that attenuate or reinforce the
atmospheric buildup of these gases.
Effects on Materials
Synthetic polymers, naturally occurring biopolymers, as well as
some other materials of commercial interest are adversely affected
by solar UV radiation. Today's materials are somewhat protected
from UVB by special additives. Therefore, any increase in solar
UVB levels will therefore accelerate their breakdown, limiting the
length of time for which they are useful outdoors.
For more information on how ozone depletion affects either human health
or the environment, follow the links below.
-
Health
Effects of Ozone Depletion
- A detailed explanation of health effects linked to to UV exposure,
including skin cancer, other skin problems, cataracts, and immune
system suppression.
-
Environmental
Effects of Ozone Depletion and Its Interactions with Climate Change
- This report by the United Nations Environment Programme's Ozone
Secretariat
explains the effects of ozone depletion other than those on human
health.
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