Lea Green 

Bastow Wood YWT


Site Details 

Recorders:  Ian Powell and Ian Court              Distance: 3008m         Walk Time:  1.5hours  

Lea Green lies just to the east of Bastow Wood and is the site of quarrying for lead and  limestone that needed a ready supply of timber for charcoal from the woods. It is also very close to Grass Wood and lies in Wharfedale.  This transect covers an area of Carboniferous Limestone near Grassington, Wharfedale that supports flora typical of limestone grassland including Common Rock Rose Helianthemum nummularium. The transect route passes through a Northern Brown Argus colony before entering Bastow Wood, one of only two Ash-Hazel woodland pastures in the YDNP.  The very thin unimproved limestone grassland and scree with some bracken 


S1 is perfect for the Small Heath and the Northern Brown Argus abounds . S2 becomes more limestone pavement and then down into a very favoured gully of S3  Thes soils are at their thinnest in S1-3 perfect for Northern Brown Argus but also  Dark Green Fritillary and Green Hairstreaks.   You then descent down the slope towards Bastow Woods  and longer grasses and scrub  and encroaching birch with patchs of Rock rose The longer grasses are perfect for the Scotch Argus and Meadow Brown. By S7 you enter woodland with grassy glades  and the grasses longer and the Speckled Wood and Vannesids favour. S9 is a green lane and hedgerow

Small Heath   favour S2 and S3.   Scotch Argus preferes S4 -5.  Northern Brown Argus along with Meadow Brown prefer S1-3 The Fritillaries favour S3-4 . Green Hairstreak is mostly S1-2 .  Common Blue S3.  The Vannesids favour woodland of S7-9 .Speckled Wood S7 Wall was spotted in S9 this year

2022 Results

County wide 2023 results reflect  the 2022 Heat and drought  with Small Tortoiseshell and Peacock nearly halved for the second year against their 5 year average. Red Admiral arrived in force in July and took advantage of soft nettle growth of the rains and had their best year ever. Drought sensitive species on thin soils were badly hit,  particularly Dark -green Fritillary and Northern Brown Argus but also Ringlet, Green-viened White and Small Heath.  Less drought affected species along with the hottest June on record built even more on gains last year leading to Comma, Brimstone, Holly Blue and most Browns  having a fantastic year reaching all time highs. A increase of 9% overall was mostly due to sheer numbers of Meadow Browns and Gatekeepers ment 2023 nearly pipped 2014 as best year in modern times.  Most noticeable was the large differeces between moisiture retaining mineral soils of the valleys and thin, dry limestone or sandy soils. A large number of damp grassland, hedgerow and woodland  dominated sites benefitted hugely with 3 sites seeing more than 50% increase . A smaller number of thin, chalky, sandy or craggy sites did badly some down up to 25%.

Lea Green did well to show and increase of 4% in numbers as so many calcareous grasslands suffered badly anything up 25% down.  The pattern of increasing numbers continues and builds on a cracking year last year!  Northern Brown Argus  was down 30% which was about typical this year and 70% down on Dark -green Frillary was pretty universal too.  In fact most trends here follow the county ones with huge increases in Red Admiral, Brimstone and Meadow Browns balanced out by equally big drops in Ringlet and Small Heath which are drought sensitive.  Great to see  Green Hairstreak have its best year in over 20!  and Wall have a superb year its highest on record here and double teh previous best, last year!  The county is seeing a remarkable resurgence of thsi species across all landscapes.  Speckled Wood exploded and Scotch Argus had another great year.  Brimstones  arrival just 2 years ago and already numbers are excellant. A remarkable site seeing remarkable positive changes.  If last year had not been quiet so dry thsi year coudl easily have beaten 2013-14 high point for this site.

Transect reports 2020

2022 Results

The best year since the 2013-14 big peak  and numbers have nearly doubled in twenty years  with teh site becoming more calacareous grassland. Northern Brown Argus has nearly doubled along with other grassland species with Meadow Brown near trebling. Brimstone was seen for teh first time this year and Orange tip  looks like it is trying hard with a big jump in numbers this year . Small Skipper  doubled over last year and had a good summer  and large skipper seemed to suffer in teh drought as it did back in  2018-19. Northern brown argus dropped back from its average after an exceptional year last year and follows teh pattern elsewhere of suffering from drought.  we should expect to drop even lower next year as a consequence, Although Small Tortoieseshel held its own while it has been near universally down elsewher Peacock halved in line with teh county, again suffering under the drought. Dark green fritillary has dropped back in numbers in teh last 10 years and was quite low this year at about a fifth of the peak which reflects teh changing habitat.

last year speckled wood boomed but fell back thsi summer under less good moist conditions. Its great to see teh wal lback these last two years after a gap of nearly 10 years. Scotch Argus has been seen spasmodicallly since 2013  but becake resident in 2019  with this year alos being quite good.  The Meadow Brown and Ringlet both boomed  doubling or treblling on last years numbers enjoying the warm June weather and reaching numbers not seen since 2013-14  while Small heath, as it did almost universally, fell back slightly.

2021 Results

2021 sees a improvement over 2020 but not quiet as good as 2019 an exceptional year.  The biggest improvemnt have been in Northern Brown Argus and Scotch Argus having bumper years . Small Heath along with Meadow Browns were up  and it was great to see the Wall returning browns

2020 Results

A pretty good year with the scarcer species holding up well with only  Ringlet  showing a decrease after the long hot summer of 2019 and drought of spring 2020 . Common Blue and particularly Small Tortoiseshell had a very good year.  NB alot of the data is based on estimates as walk frequency was low.