RICHARD WILLIAMSON: Falling butterfly numbers are the canary in coalmine

Having said in this column it was the worst year since my records began 37 years ago, things looked up in August and the year was saved in the nick of time.

Instead of being the worst year ever, it was only the fourth worst ever. The worst ever was 2001.

Twenty-six samples taken once a week over the same five-mile route give a pretty accurate record of how our best and most beloved insects are doing in this country of the south.

I started the sample in 1976 and have hardly missed a week since.

The whole of Kingley Vale is the site; its valley meadows, glades and hilltop alongside the four famous Bronze Age burial mounds, and all the shady little paths that run between.

These habitats are representative of much of the South Downs national park which is the backbone of the county.

Because Kingley Vale does not change much, unlike farmland and forestry, it’s a safe sample of Sussex decade by decade.

The best year ever was 1991, with almost four times the number of butterflies as this year. That wonderful year I logged 11,798 of them.

The meadows swarmed with meadow browns, our commonest butterfly. But there were 28 other species keeping them company.

Altogether I have identified 40 species at Kingley Vale out of the national list of 58. But normally there are 28 species. It is the richest site of any of the UK nature reserves.

I’m afraid we have lost several species over the past four decades. The small blue seems to have gone for good, likewise the adonis blue.

Silver-studded blues put in an occasional appearance, but they may only be wanderers from the heathery commons anyway. The pearl-bordered and small pearl-bordered have gone and so has the wall.

Occasionally the purple emperor has wandered into the woods, possible from the Ashlings.

The duke of burgundy has gone but never mind, it has done very well nearby and it does require that specialised habitat of cowslips in the edges of scrub. Kingley Vale cowslips are all out in the open grassland.

All over Britain 250 butterfly samples are taken and the Butterfly Conservation Society collates all the results for yearly reports.

Like the canary down the coalmine, it gives a state of the union with nature address for the nation and warnings of where things are going wrong with climate, land use, pollution and urban development.

We do not panic when we get a bad year like this one because we know we get a peak back to a high every six or seven years.

Right now it may have been a bad summer, but after a four-year low we climb back to another peak in about 2017, so that’s something to look forward to.