17
consequences
and effects
04
1
uv radiation and ecosystems
We are particularly concerned by the potential impact of increased UV
radiation on plants and animals, simply because they form the basis of
our food supply. Significant changes in the health or growth of plants and
animals may reduce the amount of available food.
Whereas scientists seem to agree that for any individu- The plants minimize their exposure to UV by limiting the
al species, changes may be observed in an organism’s surface area of foliage, which in turn impairs growth. How-
growth capacity, it is much trickier to make observations ever the observed drop in yield does not seem serious
and forecasts for an entire ecosystem. The task is com- enough for scientists to sound the alarm.
plicated by the fact that we cannot single out UV radiation
and separate it from other changes in atmospheric condi- aquatic wildlife is particularly vulnerable
tions, such as higher temperatures and CO
2
concentra- Phytoplankton are at the start of the aquatic food chain,
tions, or water availability. which account for 30 per cent of the world’s intake of ani-
mal protein. Phytoplankton productivity is restricted to the
UV radiation might affect certain species but also insects upper layer of the water where sufficient light is available.
and pests, thus counter-balancing the direct negative ef- However, even at current levels, solar UV-B radiation limits
fects of increased UV radiation. Similarly it might change reproduction and growth. A small increase in UV-B expo-
their ability to compete with other species. In the long sure could significantly reduce the size of plankton popu-
term UV-resistant plants may prevail over more vulner- lations, which affects the environment in two ways. Less
able ones. plankton means less food for the animals that prey on them
and a reduction in fish stocks, already depleted by over-
Excessive exposure to UV radiation can cause cancers in fishing. Furthermore, with less organic matter in the upper
mammals, much as humans, and damage their eyesight. layers of the water, UV radiation can penetrate deeper into
Fur protects most animals from over-exposure to harmful the water and affect more complex plants and animals liv-
rays. But radiation may nevertheless damage their nose, ing there. Solar UV radiation directly damages fish, shrimp,
paws and skin around the muzzle. crab, amphibians and other animals during their early de-
velopment. Pollution of the water by toxic substances may
Experiments on food crops have shown lower yields for heighten the adverse effects of UV radiation, working its
several key crops such as rice, soy beans and sorghum way up the food chain.
EFFECTS OF ENHANCED UV-B RADIATIONS ON CROPS
Possible changes
in plant characteristics
Consequences Selected sensitive crops
Reduced photosynthesis Rice
Reduced water-use efficiency Enhanced plant fragility
Oats
Enhanced drought stress sensitivity
Reduced leaf area
Growth limitation Sorghum
Reduced leaf conductance
Modified flowering
Soybeans
Yield reduction
(either inhibited or stimulated)
Reduced dry matter production Beans
NB: Summary conclusions from artificial exposure studies.
Source: modified from Krupa and Kickert (1989) by Runeckles and Krupa (1994) in: Fakhri Bazzaz, Wim Sombroek, Global Climate Change and Agricultural Production, FAO, Rome,1996.
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