Sweden may be trying hard to control the phenomenon of acid rain, but the end result is another crisis at hand - a dwindling Population of the moose
FOR the past 10 years, a large number of
moose are dying in southwest Sweden.
The cause for this is acid rain.
Acidification and the declining numbers
of this warm-blooded animal are being
linked because of a complex chain of
events, arising from the occurrence of
the former.
According to Adrian Frank of the
Centre for Metal Biology in Uppsala,
Sweden, acid rain is indirectly responsible for the fatalities. To counter the
effect of acidification on the environment, liberal sprayingof lime is a standard practice in the country. Since the
early '80s-, wetlands, lakes, fields, pastuies and even some forested regions
hav@ been limed following their acidification.
4 Ironically, it is the lime which has
lead to an imbalance in the concentration of chemicals like copper and
molybdenum in the animals' livers. The
useof lime was intensified in the mid'80s which corresponded with the time
kFn a large number of the animals
began signaling the coming disaster as
they contracted some diseases. The acid
rain led to the destruction of blueberry
bushes (staple diet of the moose), and the animals changed their feeding
habits. They turned to cultivated pastures and fields of oat and rape, which
were being heavily lithed by the farmers.
Frank explains that as and when
acidification occurs, it decreases the PH
level of the soil, and metals such as cadmium, zinc and, manganese - as a
result of capillary action - move up to
the top soil, getting ingested by herbivores in greater quantities. But molybdenum being less soluble in an acid-rich
environment, stays put at a lower level.
With the spraying of lime (done to neutralise the soil), the process reverses so
that the plants now receive an overdose
of molybdenum, while chemicals like
cadmium become scarce. According to
Frank, this excessive amount of molyb -
denum plays havoc with the copper
content in the ruminants' diet, decreasing it to such an extent as to lead to cop-
per deficiency, which can at times prove
fatal. The animals appear gaunt, and
sport discolored hair and impaired
immune systems. They tend to suffer
from osteoporosis, ulcers, diarrhoea,
convulsions, blindness and heart
failures.
In 1982, Frank had collected liver
and kidney samples from 4,360 moose,
shot by hunters in Sweden. His study of
14 chemicals revealed that the copper
content had gone down by 50 per cent
in- the livers of the animals, but the
quantity of molybdenum was up by 20-
40 per cent. There were significant
changes in the concentrations of other
elements like chromium, whose level
was found to be extremely low too. "The
condition of their kidneys also indicate
severe metabolic disturbances due to
the reductions in cadmium, magnesium
and manganese," says Frank.
In a paper to be published by the
American Chemical Society, Frank
extols the virtue of the moose as an
environmental benchmark. Since the
moose live on a large variety of plants,
they can be useful as reliable and sensitive indicators of environmental
changes, providing information on the
changes in the levels of all metals.
Frank believes that the people
responsible for liming should realise the
environmental consequences of doing
so not only from the point of view of the
plants, but also of the animals consuming them. But the Swedish Environmental Protection Agency has rejected
his call for an urgent nationwide investigation on the probable effects of liming on wildlife. Alternate theories project
the possibility of overpopulation or a
viral attack, as being responsible for the
declining numbers of the moose.
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