Grass Wood YWT
Grassington
Site Details:
Recorders: Nigel Heptinstall and 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
Sections:
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: 2024
Countywide, after a warm winter April turned cold, very wet and dull and everything just about stopped and it was near impossible to transect walk all month. By May there were already losses among our spring species being down a third in numbers. June brought Arctic winds, a complete reversal of the Hot June of 2023 when nine species reached all time highs here and across the UK. For the first two weeks of this June temperatures were 8’C cooler than in 2023 around a frigid 9’C with only 5 good days of sun at the end of the month. The first three weeks of July had the same theme of cool and damp with 5 warm sunny days at the end. Transect walking for many was very difficult. The persistence of the cold and damp over such a long period had a devastating effect with numerically two thirds of our butterflies in the critical later stages of their development; mortality was very high. It was also one of the longest June ‘Lulls’ lasting from late May to the beginning of July. When the main flight season did arrive it was slow to build up and there was no usual peak. Better weather in August helped save the second generation and very unusually numbers actually went up at the start of September.
Losers
For many species it was a triple whammy after the heat and droughts of the previous 2 years and last July’s poor flight period this year made it a perfect storm. Overall, annual numbers were down 41% against the average and 45% down on last year. Half our species were down more than 50% and a quarter down more than 70%. The Lycaenids, Vannesids and the Fritillaries were amongst the worst affected. Many transect walkers did not see a single Common Blue, Small Copper, Holly Blue, or Brown Argus until late into their 2nd broods.. Four of our long term declining species Common Blue, Small Heath, Small Skipper and Green-veined White had their worst year ever recorded.
The Winners and less bad losers
Northern Brown Argus had an exceptional year up near 50% Other species bucking the trend were Brimstone and Marbled White. The damp loving Ringlet on many limestone/dry sites were up a half while on most wet sites they fell by a half. However if it wasn’t for Ringlet holding up the overall numerical losses, this year would have been significantly worse. It often happens when Meadow Brown has a very poor year, like this one, Ringlet does proportionally better, and vice versa in a warm year.
It has all happened before… many times.
It was our worst year since 2016 but nearly as bad as 2009 when numbers were down 50%. 2024 comes after a run of 6 relatively good years since 2018 along with rapidly rising temperatures including 2 of our hottest summers which were followed by two of our best butterfly years in 2019 and 2023. It is likely 2024 was a blip
Grass Wood did a tad worse than the county average. Proportionally Northern Brown Argus did slightly less bad as did Speckled Wood This is the pattern seen elsewhere although on some sites NBA have done extremely well this year. Unfortunaly Dark Green Frit were not seen thsi year and has had a disasterous year disappearing from some sites.
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.
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. 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.