The species with the biggest declines:
Change since records began

Change since records began
Heath
fritillary
1
Small
tortoiseshell
-88%
Small
tortoiseshell
-87%
-87%
2
Wall
-83%
3
White-letter
hairstreak
-80%
4
Wood
white
-78%
5
White-
letter
hairstreak
Small
pearl-bordered
fritillary
6
-74%
-80%
Small skipper
-73%
7
Heath
fritillary
Grayling
-72%
8
-88%
Pearl-bordered
fritillary
-70%
9
Wood
white
High brown
fritillary
-78%
-66%
10