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In some countries the numbers of glow-worms have been falling. Evidence suggests that there has
been a steady decrease in the British glow-worm population since the 1950s and possibly before
that. Possible causes for the decline include habitat destruction, pollution and changes in climate.
Thousands of acres of grassland have been built upon and glow-worm sites have become
increasingly isolated from each other. The widespread use of pesticides and fertilisers may also
have endangered the glow-worm. Being at the top of a food chain it is likely to absorb any
pollutants eaten by the snails on which it feeds. The effect of global warming on rainfall and other
weather patterns may also be playing a part in the disappearance of glow-worms. A lot more
research will be needed, however, before the causes of the glow-worm's gradual decline are clear.