Grass Wood YWT


Site Details:

Recorders:  Ian and Barbara  Blomfield                        Distance:  1970m                 Altitude 283m.         Walk Time approx:  50mins

Grass Wood is one of the largest areas of broadleaved woodland in the Dales and one of its richest. It is just to he north of Grassington village. It is situated on the west and south facing slopes of a bench of Carboniferous limestone, and so the woodland grows out of limestone scars, limestone pavement and scree. Beech, sycamore, spruce, larch and pine were planted into the woodland in the twentieth century and these are gradually being removed to restore the wood to its natural canopy composition of ash, wych elm, oak and hazel. The ground flora  is particularly species-rich including lily-of-the-valley, stone bramble, mountain melick, common valerian, wild angelica, salad and great burnet, melancholy thistle, lady’s-mantle, angular Soloman’s seal, common rock-rose, bloody crane’s-bill and betony.  It has a very rich butterfly and moth fauna  including Norther Brown Argus.  Bastow wood immediatly to the east is another extremely good site with a large population of NBA


It is section 3  before the butterfly numbers begin to climb with Speckled Woods predominating along with Ringlet.  S5-S6  grassy south slopes into the small valley  is where Northern Brown Argus begin to be seen and the highest  section totals counts along with S8  is the  most wooded section with lareg numbers of speckled woods . The slope back into the valley at S9 also sees  Dark-green Fritillary  and NBA . The damper valley bottom of S10 and 11 yield  much larger numbers as you would expect of Green-viened Whites and  even Orange Tips.

Results: 2023

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%.

Grass Wood had a good year rivalling 2019 with a  50% increase in overall numbers following the pattern of the last decade.  The big winners were the browns with Ringlet bucking the county trend and increasing . Speckled Wood had a record breaking year and on thsi site has almost trebled in the last decade that might indicate scrub and tree ingress.   Big losers were Dark-green Fritillary that tanked universally disliking last years drought . Red Admiral here didnt see the big influx seen elsewhere and surprisingly was well down. In contrast  Comma boomed which it did universally .  Northern Brown Argus was down substantially as it was universally  along with all the Whites  Brimstone showed a good increase and had it best showing ever in Yorkshire this year. 

Transect reports

Results: 2021

2021 was up  a very large 25% against teh average and well up on last year and and not so far away from the cracking year 2019. Only teh skippers were down which they were in many localities , Interestingly  the whites, the vanessids, northern Borwn Argus and dark green fritillary were all up bucking the trend over most of lowland Yorkshire. Its great to see the threatened species small heath return.  In terms of numbers  most of the increase is down to Ringlet and Speckled wood  both having their best years since 2019. This is one of the very few sites that saw Peacock increase. The reasons are likely the temperatures were much less extreme here than in the lowlands  and may not have experienced the  drought.

Results: 2021

2019 remains an outstanding year  and has a big influence on the 5  recorded year average not helped by the absence of results from 2017 and 18 , a period of quite quick changes in habitat by 2019 easily seen by the very large number of Speckled Wood and Ringlet . However we can say 2021 was a little down on 2020 mostly because there has been a dip in these two species  along with the whites.  Northern Brown Argus and Green Hairstreak reappeared in 2020 and is being maintained.  brimstone did very well as it did in most transects . Dark-green Fritillary also maintained good numbers.  From the rarer species point of view it is an improving picture.