Tag Archives: Mangrove Swamp

Conservation, Nature Reserves

Keeping Chiswick’s Wet Woodland Wet

Sedge removed (a tuft still visible bottom right), much mud still to scoop out …

Well, it’s late November, the animals aren’t breeding, and the flowers are mostly not flowering (Rowan and Cotoneaster are honourable exceptions). So, it’s the perfect time for clearing out the Wet Woodland (Carr) to keep it looking, well, Wet, rather than getting more and more overgrown and full of leaf litter until it turns into good old ordinary dry woodland, or Mixed Temperate Forest as an ecologist would say.

Mudscooping the Wet Woodland (aka the “Mangrove Swamp”)

There’s always a debate about why we do this sort of thing. Shouldn’t we just do George Monbiot’s Rewilding thing and leave nature alone? Well, we could. Then the reserve’s pond, wet woodland, meadows, grassy banks, and demonstration flowerbed would all go through the succession to mixed woodland, and we’d have an end-to-end canopy of trees: not a bad thing you might say.

But we would lose much of the diversity of habitats and of species – no pond life, no grassland flowers or grassland butterflies, for instance. In a large enough area, that would be fine: the rivers would flood and meander, create new oxbow lakes, mudflats, and shingle banks, which would be colonized and grow up into varied ponds, wet woodland, meadows, and forest, just as you’d hope.

Muddy but Happy!

Only one small problem: you need to include a river’s catchment area and flood plain in the reserve. That’d be the whole of Oxfordshire, Berkshire, and London, roughly…

So, to be practical, in an urban nature reserve you only get a small area to conserve, to allow people to visit to see and feel and smell and touch nature, and to teach children (and adults) about nature. Those are worthy aims, and they’re the raison d’etre of London Wildlife Trust. To manage that, one needs to maintain a bit of diversity of habitats and of species for people to see and learn about. And that means holding back the natural succession so that not every inch is a tree canopy, splendid as canopies are. And that means having volunteers scoop mud, mow grass, and pull out tree seedlings, all the while trying to leave enough seeds, eggs and other life-forms in place for the reserve to burst back into life at all stages of the succession.

Yes, we know George Monbiot calls all that “gardening”: but really, it’s not. We’re just creating the conditions for nature to do its own thing, or rather, a lot of its different and wonderful things.

Chaotic patterns of wet mud running into erosion gullies down the flat face of a wheelbarrow. The pattern forms within a minute of tipping mud from the barrow: different every time, but always giving the same wonderfully beautiful natural result.

Actually, one can hardly help letting nature do its thing. It does it even in the mud in a wheelbarrow!

Natural History, Wildlife

Summer’s End Wildlife at Gunnersbury Triangle

Buff-tip moth caterpillar Phalera bucephala, top
Buff-tip moth caterpillar Phalera bucephala, top (22 September)

Buff-tip caterpillar, side view: fully 70 mm long
Buff-tip caterpillar, side view: fully 70 mm long

White Ermine caterpillar Spilosoma lubricipeda
White Ermine caterpillar Spilosoma lubricipeda found in the anthill meadow

Handsome Ichneumon, similar to but not I. stramentarius
Handsome Ichneumon, similar to but not I. stramentarius, which lacks the yellow crescent marking on the thorax.

Plump Frog
Plump Common Frog

A big Funnel fungus Clitocybe
A big Funnel fungus, perhaps Frosty Funnel, Clitocybe phyllophila

Oak Gall, seemingly Marble Gall, though cracked
Oak Gall, seemingly Marble Gall, though cracked

Mining bee Lasioglossum on Ragwort
Mining bee Lasioglossum on Ragwort

Robber fly Dysmachus trigonus (Asilidae)
Robber fly Machimus atricapillus (Asilidae)

Yellow Iris fruit (nibbled seed pod)

Common Darter
Common Darter

Mangrove Swamp, wet
The “Mangrove Swamp”, wet and pretty. No air-breathing roots, though.

Conservation, Nature Reserves

Opening up the Mangrove Swamp

Today, down at the nature reserve, it was a day for work and weather rather than natural history. A vigorous Low was working its way across the top of Britain, with a brisk, freshening southwesterly wind bringing little showers across town. The water table had risen appreciably in two days, and I was glad of my gumboots, as I had decided it was time to do something about the overgrown ‘Mangrove Swamp’ in the middle of the reserve.

I should explain at once that we don’t have any coral reefs or fringing banks of Rhizophora mangroves here in Chiswick: that would be a fine thing. What we do have is a wet hollow – probably once a tributary of the long-gone Bollo Brook, one of London’s lost rivers – with attractive carr vegetation. Carr means wet woodland: we have willow of various species (probably mainly crack willow), birch and an assortment of other trees in the drier places – sycamore, hazel, holly, rowan, cherry, oak. But down in the Mangrove Swamp the willows predominate, their feet in the water for half the year. They grow rapidly, and then fall over; or branches get shaded out and die. The result, quite soon, is a tangle of lodged trunks and dead wood that cuts off the view and fills up the hollow, part of the natural succession, but tending to make the reserve less diverse (I think) and less interesting to look at. (I’m reflecting on whether one should be “managing” a “nature reserve” at all, given what George Monbiot says in Feral – he’s all for leaving nature to itself – but in a small reserve in town, management does seem necessary. Perhaps it’s a nature garden or something, not really a reserve at all.)

I cleared a mass of broken or cut dead wood from the wet floor, putting it to one side – it will still be available for fungi and beetles to consume. I then cut several long, heavy willow branches, mostly dead or dying, that had fallen most of the way to the ground across the mangrove swamp. A couple of hours hard work (I completely forgot about the brisk wind) had the main area cleared. We then set to and cleared what seemed to be a dark shrubbery near the boardwalk, but which was actually a large fallen tree shrouded in a six-foot thick mass of ivy. It was satisfying to get it clear; the tree trunk will need chainsawing, however.

After a well-deserved cup of tea, I pruned the hedge that was overhanging the street, pulling down a mass of strong twining hops that had scrambled all over the hawthorn. Blood-red haws rained down but there were plenty left when I had finished. Around the reserve, the rowans were in fine fruit, with some roses covered in scarlet hips.