Stratospheric Ozone Depletion - The Changing Arctic Environment: The Arctic Messenger - page 115

at mid-latitude in the Northern Hemisphere in the future than in 1980, health scientists and
practitioners could find themselves worrying about the possibility of widespread vitamin D
deficiency.
Environmental effects have been more difficult to evaluate than those related to hu-
man health, partly because of the difficulty in collecting information but also because sea-
sonal variation in UV irradiance complicates the detection of long-term impacts. What fol-
lows is a selective summary of what is known.
It has been rare to have information directly related to Arctic UV impacts. However,
a recent meta-analysis of several studies examined the response of mosses and flowering
plants from the Arctic and Antarctic to varying UV-B irradiance. The authors concluded
that plants responded to increased UV-B by reducing leaf growth and area by about 1% for
each 3% of increased UV-B irradiance. By extrapolation, this suggests that in such areas
as the southern tip of South America, where a 20% increase in the summertime UV-B has
occurred, plant growth decreased by up to 6% between 1979 and 2009. This estimate is
roughly as would be expected from observations elsewhere and from experimental stud-
ies. If you would like to know more, take a look at the reference in the bibliography by
Newsham and Robinson. There is good evidence to support the theory that the reduction in
plant growth occurs because the plants are redirecting their energy to UV radiative protec-
tion mechanisms, such as the production of UV screening resins, antioxidants and for DNA
repair. For example, the increased production of UV-absorbing compounds in an Antarctic
leafy liverwort was calculated to require 2% of the carbon photosynthesized by each plant.
This is not a huge proportion, but remember that these plants are not living in a friendly
environment. Perhaps a better indication of the cumulative cost of metabolic protective
measures comes from studies on a Patagonian shrub: Grindelia chiloensis . When the plants
were artificially screened from natural ambient UV-B radiation, they responded by grow-
ing taller, putting on more biomass and increasing their leaf area. This was correlated with
a reduction of 10% in the energy used in the synthesis of UV-B protective resin.
Less vegetative biomass can be expected to have impacts on the food chain. The 2005
Arctic Climate Impact Assessment (ACIA) describes how this can even result in changes