A couple of weeks ago I waxed happily sarcastic about the wartime National Census of Fruit, which happened in 1944. Beginning on Saturday there is another census, which everyone in the UK can join in on and which I shall not be sarcastic about at all. It is the National Census of Butterflies.
It is called the Big Butterfly Count. It was launched in 2010, when 10,000 people took part and counted 210,000 butterflies and day-flying moths across the nation. (A map of what sort of butterflies they found and where is here.) The organisers hope that many more people will join this year's big butterfly count, which runs all week, from 16th-31st July 2011.
Sir David Attenborough has a buddleia bush in his garden. Twenty years ago it was covered in Red Admirals. Last year he saw just one. Butterflies have been declining catastrophically, in Britain and around the world. How fast? Obviously one needs a census to find out. But this, believe it or not, is about more than butterflies. Because butterflies are sensitive little creatures. A small change in the environment can cause a big change in the number of butterflies. And these changes happen quickly, year on year. This means that butterflies are brilliant for telling us what is happening in the countryside (or, for that matter, in the towns: town gardens can contain many more flowering species than some vast hedgeless stretches of countryside arable prairie. Ask bee-keepers: London bees do very well and London honey can be excellent.)
That sensitivity and speed make butterfly numbers significant for more than butterflies. Butterfly declines are an early warning for other wildlife losses. Technically, they are excellent indicators of biodiversity. Biodiversity is such a hugely complex phenomenon that it is almost impossible to measure - but such an important phenomenon that we desperately need ways to measure it.
The solution is to use proxy measures, such as butterflies. Farmland birds are another good indicator of biodiversity – see Significance, Sept 2006. Woodland birds, on the other hand, are not – they are just too adaptable.
But butterflies’ sensitivity and speed of reaction makes them ideal biodiversity indicators. That is why the organisers describe counting butterflies as taking the pulse of nature. The count will also help to identify trends in species that will help gauge the effects of climate change and plan ways to protect butterflies and day-flying moths from extinction. More than 20 species of day-flying moths have gone extinct in Britain in recent years.
So join the Butterfly count. Children can do it, teachers can do it, and schools can do it any and every day next week before they break up. Parents can do it, everyone can go out and do it and fill in the results on-line. Don’t trust just me. Trust the great and good Sir David Attenborough, who was talking about it on BBC Radio this morning, here. (Click on it anyway. It is always such a pleasure to hear that man’s voice.) Then sit in your garden, or on your balcony, or in your local park for fifteen minutes on Saturday or thereabouts – I hope it keeps fine for you.
And I hope – rather against hope, but still – that you spot lots of butterflies.