Tag Archives: HImalayan Balsam

Riversearch June 2016: Alien invader – Japanese Knotweed

The main challenge with my Riversearch survey in June was seeing the river – since my previous survey, the plants along the riverbank. have shot up. There were stinging nettles taller than me, and inpenetrable thickets of bramble blocking me from getting close to the river in many places. Still, I did manage the occassional glimpse of the river – enough to see that, though the river level was normal, it was still quite turbid.

Intriguing holes in the riverbank

There weren’t any particularly exciting wildlife sightings to report, although I did spot some intriguing holes.

 

I did see a couple of invasive non-native species –  Himalayan balsam, as usual, and a probable sighting of Japanese knotweed. This is the first time I have spotted Japanese knotweed along by the river, and I had to use binoculars from the opposite bank to see it, so I’m not 100% sure about my identification. But I’ve shared the photos with the wildlife trust, who seem to think it is knotweed. I don’t know if it’s new here, or if I spotted it this time and missed it previously because I was doing my stretch in the opposite direction to normal. Anyway, that’s now been reported to the National Trust, who own the land, so hopefully they’ll be able to sort it out swiftly.

Japanese knotweed?

Japanese knotweed doesn’t look particularly startling (unlike Giant Hogweed), but it can be a big problem, spreading quickly and hard to get rid of. In urban areas it can grow up through patios or conservatory floors, so it’s not something you want in your garden. In the countryside it can quickly overwhelm native species.

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August Riversearch: more Himalayan Balsam

I timed my latest Riversearch survey well today. Yesterday it was just too darned hot, and it rained a lot of this morning, but this afternoon,  after the rain, there was a brief period of steam and solitude. In addition to the usual surveying the River Mole for signs of pollution, invasive species and, optimistically, hints of otters or water voles, I was also carrying out a recce for a more indepth water vole survey I hope to do later this week.

Himalayan Balsam by the River Mole at the foot of Box Hill
Himalayan Balsam by the River Mole at the foot of Box Hill

Before I get too distracted by water voles (or the absence of them), here’s how the Riversearch survey went. I’d just turned off the pavement onto the meadow by the river when I spotted my first animal: a small, bold mouse. By its size it must be a juvenile woodmouse. It was surpisingly calm, and let me approach to within a metre before retreating to a safer distance (1.5 metres – I must look quite unthreatening).

I was pleased to see there was no one sleeping rough under the bridge this time (particularly since the river level has recently been over the ledge where the person was sleeping last time I surveyed).

It must be a good time to be a fruit and/or nut-eating animal or bird at the moment – the brambles were laden with blackberries, and the trees have started dropping acorns and hazelnuts. But I saw and heard little in the way of bird life – a couple of crows and a duck.

Lots of blackberries
Lots of blackberries

There were no obvious signs of pollution in the water, and the river was relatively clear (the Mole is hardly a sparkling example of water purity, but the recent rains have obviously not muddied it too much). The bad news is there were lots of small pockets of Himalayan Balsam all along my stretch. I spoke to an angler who fishes up near Gatwick, and says there’s lots up there. All this is bad news further downstream – I know in the last couple of years they’ve been doing lots of work to get rid of it near Leatherhead, but the seeds are carried by water, so it will just keep coming back unless the upstream patches of it are tackled.

Himalayan Balsam
Himalayan Balsam

Apart from that there was little else to report – a few more riffles than normal (that’s a good thing as they oxygenate the river), and quite a bit of litter where people have been picnicking by the river. I even came across an abandoned rubber dinghy. I really can’t understand why, when you choose to spend time in a place because it’s lovely and unspoilt, you’d then leave behind your rubbish to spoil it for others (and more importantly, pose a hazard to wildlife).

Abandoned rubber dinghy
Abandoned rubber dinghy

To carry out our water vole survey (as part of Surrey Wildlife Trust’s ‘Vole Patrol’) we’re going to need to get into the river, so I was scoping out whether the river is shallow enough to do so, and whether we’ll be able to get in and out ok. Along most of the length of my stretch the banks are very steep, but there are a few spots where there’s a more gentle slope, and the river should be manageable in waders. I’m hopeful that, provided there’s not too much rain over the next few days, we’ll be able to survey it without the need for a boat (I suspect the rubber dinghy’s been abandoned for a reason, so I’m not sure I’d trust it enough!). More of that, if it happens, later.

In the meantime, I must remember to send my survey data to the Riversearch team, and clean my wellies to make sure there’s no quagga mussels clinging to them…