Temperamental Mole

Ecological consultant Rebecca, taking water samples under the netted section of the River Mole

A tributary of the River Thames, the River Mole rises just south of Rusper village in West Sussex, flowing north-west for 50 miles (80km) before reaching the Thames at the north Surrey border.

At Gatwick our section of the River Mole is rather open and slow-flowing, passing under the airfield through a tunnel and exiting on the north side. At the southern point where it enters, a Kingfisher is regularly spotted zipping in and out.
   The course of the Mole has been altered several times since the airport began operating commercially in 1945. During a massive flood alleviation project in 1999 it was diverted once more from its course north of the airfield; now it travels west for 400m parallel to the taxiway before meandering in a north-easterly direction. With a good diversity of riffle formations, pool sequences, backwaters, lush wet grassland and reedbeds, it is in my opinion quite a lovely and natural-looking section of river.

The River Mole on Gatwick's Landholdings, north of the airfield

Vantage point from the grassy mound, overlooking the airfield - NWZ

Reedbeds in winter

The water level at Povey Cross has reached level 2 (my cunning theory is that the numbers represent 10cm, putting the water level at 1.2m.) In the past I have seen the water close to over-topping the stick.

Much of the catchment area of the Mole lies on impermeable rock, meaning that the water level responds extremely rapidly to heavy rainfall. My first week of surveying at Gatwick taught me a punitive lesson… a few of my reptile mats have probably washed up somewhere in Surrey.

Rebecca kicking the silt and netting the river-dwelling invertebrates

The water quality of the river can also fluctuate greatly depending on the season. The ecologists Rebecca and Victoria from Penny Anderson Associates regularly carry out aquatic invertebrate 'kick surveys', taking samples back to the lab for species identification under the microscope. Identifying the flora and fauna occurring in the waterways is particularly useful, as certain species are very sensitive to pollution and could act as indicators of any negative impacts of the airport's operations. On Monday they visited Gatwick and I was able to join in to see how it is done.

Damselfly nymph covered in silt - possibly a Banded Demoiselle?

Common Backswimmer (Notonecta glauca)

Diving beetle species

A small leech

Freshwater Shrimp (Gammarus pulex) is a type of amphipod crustacean

An Orb Mussel, a type of freshwater mollusc

I particularly enjoy this time of year when the Reed Warblers set up their territories all along the Mole. If you happen to wander west along the public right of way from Povey Cross you can hear their repetitive, mechanical sounding song...

I took this photo of a Reed Warbler along the Mole last summer -

 possibly my best birding photo so far!

And finally, one of the mystery coconuts which wash up regularly along the River Mole... No explanations have sufficed so far, but it gives me a hankering for lime and a tiny little umbrella.

A rarer-tree… The native Black Poplar

Black Poplar Species Action Plan

We have a new species at Gatwick! We know this because we put it there... Last Wednesday under the supervision of expert plant carer Nikki Coultrip from JS Agriculture, we planted our 10 rare native Black Poplar saplings along the River Mole floodplain.

The full scientific name is Populus nigra subsps betulifolia. This tree is native to the UK and is one of the rarest in existence; only a few thousand mature specimens remain in Britain and 33 of these exist in Sussex.

Buds still in their dormancy

We have followed the planting guidelines of Sussex Otters and Rivers Project and the next few years we will be keeping a close eye on these little guys, strimming the grass around their tree guards and making sure they are not swamped by surrounding vegetation.

Each got a pep talk: Reach for the skies, don't let those rabbits get to you,
keep your head above the flood waters

Centuries ago the British black poplar would have occurred naturally in floodplain woodlands. Unfortunately, naturally functioning floodplain woodlands are almost an extinct habitat, also this tree requires very specific conditions to reproduce and so right now only survives through plantings and cuttings.

The Sussex Black Poplar Working Group was established in 1998 and to date have planted over 4000 trees in Sussex river valleys. Every year along with Sussex Otters and Rivers Project, they help to hand out young black poplar trees to landowners who can plant them in their native habitat. You can find more info about the SORP at http://www.sussexotters.org/