Aciiiiiiiiiiid! (Part One – The Fluffy Bit)
Whenever I read stuff about the Olympics, the words ‘Acid Grassland’ turn up. It’s very rare you know. It’s grass land. And it’s Acid. And I nod my head wisely and agree. We have to protect the rare Acid Grassland. But as I was wandering through the rare acid grassland the other day it occurred to me – what actually is it?
I mean – it’s very pretty – lots of different varieties of grasses and – good word here – sedges – plus some interesting-looking moss, and it does look different to the bog standard grass in the rest of the park. But what makes it so different and why isn’t it anywhere else?
My first consultation was the Phantom-grade (.i.e. children’s) Holiday Geology Guide, a splendid little introduction to what’s really deep down under Greenwich, which tells me that most of us down the hill are on general sand and gravel, some of us are on the engagingly solid ’Woolwich beds’ – about 10 metres of clay and sand that were deposited about 10 million years ago. Water coming down from the top of the hill can’t pass through the Woolwich clay, so bursts out of the land where it can, as springs – which is what our forefathers channelled through all those intriguing ‘secret tunnels’ I’m always banging on about.
Under that, and further up the hill, Thanet Sand appears – about 17 metres of it and about 60million years old, and under that, lies 180m of chalk – limestone left by warm seas washing over us 85 milion years ago (the leaflet is nothing if not romantic…)
But, Holiday Geology also tells me we’re on a fault line – The Greenwich Fault – how cool is that? which means that when we were all mashed up (sometime around when the Alps were created) different bits of rock were brought nearer to the surface in some places to others.
Looking at the handy disected map on the single A3 piece of card that is Holiday Geology (and easily worth the £1.99 I paid for it in the visitor centre yonks ago), it looks as though the bit roughly around the Crooms Hill end of the park is yet another type of ground, also known as Blackheath Beds – a thinnish cap to the hill, consisting of sand and little round flints, called, apparently, ‘Blackheath Pebbles.’
Now, this has to be the ground on which that Acid Grass grows. But this is also where Holiday Geology runs out for me. So I grew up a little and took 1970s secondary school geography, my guide a text book discarded by St Theresa’s Secondary School called South East England: Thameside and the Weald, by Roy Millward and Adrian Robinson. Frankly everything about it reminds me why I hated Geography at school – even the smell of chalk (I suspect from the blackboard rather than a field trip) lingers in my charity-shop find but it does have a good chapter on the topography of Greenwich.
It talks about the seedlings that were gathered for Greenwich Park’s reinvention in the 17th century, and how many of them were brought over from France via Lesnes Abbey, and have ‘flourished on the light, well-drained soils of the Blackheath beds’, but the wild plants in the South Eastern side of the park have been there for much longer than that. You only have to look down to see just how many varieties of plant are within a single metre of soil in that part of the park.
Gravel and good drainage are ideal for acid-loving plants (the chalk is far too far below ground to be a problem) and the acid grassland over at the Crooms Hill end of the park is a rich mix of all sorts of curious little specimens that have a much more heathy feel to them than the other, lusher plants elsewhere because the soil is so thin in that part. I guess Blackheath itself would have been like it too, before the war, but since it’s been filled in with bomb-rubble and turned into a giant billiard table, the only acid grassland of any substance left round here is in the park.
This super-rare-factor is made worse in the rest of London because the gravel these little plants like is also enjoyed by developers who find it ideal to build on (and with). Other enemies of acid grassland are pollutants (of which there aren’t too many in the park itself, of course) and dogs – whose urine is like weedkiller to these delicate little grasses.
There is one other thing that might give them a bit of a headache though…
Horses’ hooves. The soil is thin, the plants are thinner, which is why NOGOE have been so keen to talk about the Acid Grasslands. Of course, Royal Parks know the importance of this area and they’re doing their best to manage an area whose significance hasn’t been appreciated in years gone by. And LOCOG have been told in no uncertain terms to keep away from there.
But folks. There is a second part to this story. I’ll post as soon as I’ve written it…
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