Sparrows and canaries

As Sigmund Freud nearly said, there is something deeply unfunny about jokes. A certain levity greeted our Save Our Sparrows campaign. However, on our part there was an underlying seriousness of purpose. It is now evident that sparrow numbers in many big cities in Britain have collapsed over the past decade by as much as 90 per cent. If this were a sparrow-specific phenomenon, for example caused by a disease which affected one bird species only, then it would be a shame, but no big deal.

As Sigmund Freud nearly said, there is something deeply unfunny about jokes. A certain levity greeted our Save Our Sparrows campaign. However, on our part there was an underlying seriousness of purpose. It is now evident that sparrow numbers in many big cities in Britain have collapsed over the past decade by as much as 90 per cent. If this were a sparrow-specific phenomenon, for example caused by a disease which affected one bird species only, then it would be a shame, but no big deal.

On the other hand, there is the possibility that the decline in sparrow numbers is a warning of some wider ecological disaster.

One of the most plausible hypotheses advanced so far to explain this mystery is that some of the constituents in unleaded petrol, such as benzene, are becoming concentrated in urban atmospheres. It would be a piquant irony if unleaded petrol, one of the great green victories, should turn out to be the villain of the piece. But it would not be the first time: banning DDT may have contributed to malaria's comeback. Green politics is no simpler than any other kind.

The Government is about to award a research contract to investigate the decline in sparrow numbers: this theory must be central to the investigation.