July 2024

Sadly, a visible  bacterial bloom of Aphanizomenon flos-cuculae had developed in the lake when I took a look on 26th. Contact with this blue-green should be avoided. Water clarity was 750mm, a decline from early summer, as evident also in the last five summers. 2019 was the last year when water clarity remained high through the summer. These blooms are caused by high levels of nutrients in the lake water, perhaps exascerbated by water temperature. Just what has caused the increase in nutirents is not known, because there is no monitoring of nutrinets in the three main tributaries of the lake (typical of the Environment Agency elsewhere, unfortunately). It is possible that the increase is from the flow of the AELTC drain, from diffuse sources in the rest of the catchment, or from disturbance of the sediment on the lake bottom caused by waterweed clearance. It is most strange that AELTC and LB Merton express concern over lake water quality and have proposals to exascerbate the problems, but have done no work to diagnose the cause! Ticking the box will not solve the problem. Indeed, the watersports people had recently removed waterweed from the lake and left it in untidy heaps on the prominade. Such removal risks disturbing the sediment and liberating nutrients that would otherwise remain locked away a depth.

I did my bird count on the 26th. Things were quiet, with most breeding over and little song. Remarkable, however, was thirty Swifts hawking insects over the lake. This big number could have included birds already on their way to central Africa where they spend most of their annual cycle, as well as later birds still commuting to and from their nests all over this quarter of London. Swift populations are very difficult to monitor because they travel long distances to flock at feeding sites, but it's noteworthy that this is the third largest July count at our lake and those two larger counts were in recent years, 2011 and 2023. So, there is little local evidence of the claimed decline in UK populations.

There were around 50Adult Black-headed Gulls and just five young of the year. Interestingly, whilst mot of the adults had already moulted their head feathers to loose that black head, a few were still in breeding plumage. I can only speculate why this may be so. Perhaps this reflects breeding failures at differing times, non-breeding one-year-old birds returning earlier, or birds coming from distant places with differing timing. 

The count of 11  Canada Geese was the third lowest July tally over the 39-year study, suggesting a decline in summer numbers, but counts are very variable, so we await a detailed examination for confirmation.

The gates were opened at around 06:55. Most of the flow of the brook was down the new courses, both upstream of the toilet block and within the Crazy Golf area.

Summer flowers were evident: Yarrow in the long grass areas, Cornflowers surviving from previous years in the Hormbeam plots beside the perimeter path in the north-east. Visible through the northern hedgerow, one could see a mass of flowers of Wild Carrot on the 9th tee of the ex-golf course and a few purple flowerheads of Common Knapweed, a native species which provides much nectar for pollinators.

My monthly assessment of the Lofthouse Glade gave 144 species, showing no increase since October last year. So, the accumulation of species has slowed. The number of species found in any one monthly visit is now averaging around 30, which is only a slight decline since monitoring began in 2016. A stand of Great Willowherb and some tall Ragworts provided a splash of colour there. Unfortunately, no-one has chosen to reverse the excess mulch around the path at the southern end of the glade, damage that is readily reversed. 

On the 29th a large Ash growing at the edge of the brook west of the toilet block was taken down. A subsequent ring count revealed an age of around 275 years, so it began life around 1849, around the time that the park was purchased by Beaumont, although it had been in agricultural use since around 1827, when the Spencers became abseentee landlords. Doubtless this historic tree had to come down because it grew right by a well-used path and had a little die-back in its crown, probably the first casulty to the diesease in the public park. It was probably a survivor from the part of Ashen Grove Wood that once extended through this area up as far as the present-day bowls pavilion. The loss has opened up a big area to the sky, presenting an opportunity to restore woodland back to the area.