July and August is a good time of year to spot butterflies, because this is when most species are at the adult stage of their lifecycle and so are more likely to be seen.
Butterflies react very quickly to changes in their environment. This makes them excellent biodiversity indicators, with butterfly declines being an early warning for other wildlife losses.
This makes the survey invaluable as a way of assessing the impact of climate change – not just on butterflies, but on all sorts of wildlife.
The survey also helps to identify trends in species that will help Butterfly Conservation plan how to protect butterflies from extinction.
This year's Big Butterfly Count was launched on Friday 19 July by conservationist and broadcaster Chris Packham, and will take place until Sunday 11 August.
Other celebrities backing the project are Sir David Attenborough, President of Butterfly Conservation; Alan Titchmarsh MBE; Mike Dilger and Nick Baker, Vice Presidents of Butterfly Conservation; and Joanna Lumley, OBE.
For more information visit www.bigbutterflycount.org.