0:00:33 > 0:00:35Once upon a time, the Welsh mined coal.
0:00:35 > 0:00:38These days it's sand they're after.
0:00:38 > 0:00:39And lots of it.
0:00:44 > 0:00:4885% of the sand that we use is taken from the sea bed.
0:00:49 > 0:00:51I'm going to find out what effect that's having.
0:00:52 > 0:00:55I'm in the Bristol channel and we're heading out
0:00:55 > 0:00:59to Nash Bank, which is about five miles off the coast of south Wales
0:00:59 > 0:01:01and I'm gonna get on that, which is a dredger.
0:01:01 > 0:01:04I've watched these ships going up and down since I was kid,
0:01:04 > 0:01:07but I've never been on one so I'm excited.
0:01:07 > 0:01:11'The Arco Dart spends 360 days a year
0:01:11 > 0:01:13'dredging up sand and pebbles from the sea bed.'
0:01:16 > 0:01:17- Hello, Alice.- Hello.
0:01:17 > 0:01:20Mick Forster, master of the Arco Dart. Welcome aboard.
0:01:20 > 0:01:22- Thank you. - Would you like to come over?
0:01:23 > 0:01:27It's Mick Forster's job to position his ship precisely
0:01:27 > 0:01:29over a sand bank.
0:01:29 > 0:01:31Can you dredge anywhere in the Bristol Channel?
0:01:31 > 0:01:35No. We're restricted to what we call dredging areas.
0:01:35 > 0:01:37We're only allowed to load on a licensed area.
0:01:37 > 0:01:41- So does this blue streak here represent a bank of sand?- Yes.
0:01:41 > 0:01:45This is where we're heading for, called the Nash dredging grounds.
0:01:45 > 0:01:46The sea bed is owned by the crown
0:01:46 > 0:01:50and every tonne of aggregate taken has to be paid for.
0:01:53 > 0:01:55The Nash Bank is eight miles long
0:01:55 > 0:01:57and a mile wide.
0:01:57 > 0:01:59That's a lot of sand.
0:02:01 > 0:02:04The dredge is, basically, an enormous vacuum cleaner.
0:02:04 > 0:02:091,300 tonnes of aggregate are sucked up this tube every two hours.
0:02:09 > 0:02:12As it's pumped aboard it gets graded.
0:02:12 > 0:02:16Sand for cement, gravel for gardens.
0:02:18 > 0:02:21The dredging companies are required to do detailed surveys
0:02:21 > 0:02:23to try to measure the effects
0:02:23 > 0:02:26of their operations on the local environment.
0:02:26 > 0:02:30This is a chart of the sea bed. It shows the bank very clearly.
0:02:30 > 0:02:34Erm, the Nash Bank itself, is this area here.
0:02:34 > 0:02:39After you take sand out from this area, is it being replenished?
0:02:39 > 0:02:42You must remember, there are no renewable sources of sand.
0:02:42 > 0:02:45- Just like oil.- No. - There's no renewable sources of oil.
0:02:45 > 0:02:49Erm, you just must use those resources carefully.
0:02:49 > 0:02:53The sand in Nash Bank was made in the last ice age.
0:02:53 > 0:02:56If the visibility of the water was better,
0:02:56 > 0:02:59we'd be able to see that the sand lies on the sea bed
0:02:59 > 0:03:02in remarkable 20 meter high waves,
0:03:02 > 0:03:04gradually being eaten away by dredging.
0:03:08 > 0:03:15Since the 1920s, one fifth of the Nash Bank has already been consumed
0:03:15 > 0:03:17and it will never be replaced.
0:03:19 > 0:03:22We may not be taking precious sand directly from our beaches
0:03:22 > 0:03:25but some worry that dredging sand banks
0:03:25 > 0:03:30unleashes the power of the sea to erode beaches away.
0:03:31 > 0:03:35Can you be absolutely sure that if you remove the sand down here
0:03:35 > 0:03:38it's not going to have an effect on the coast line?
0:03:38 > 0:03:42These beaches have been changing for thousands of years.
0:03:42 > 0:03:45They've been coming, going. Yet we see a change in our...
0:03:45 > 0:03:49perhaps on a decade and we think it's important, but actually it isn't.
0:03:49 > 0:03:52That change has been occurring over many, many hundreds of years.
0:03:54 > 0:03:57Whatever the effect of dredging, one thing is for sure -
0:03:57 > 0:03:59sand is a finite resource.
0:03:59 > 0:04:02Once it's gone, it's gone for good.
0:04:04 > 0:04:06But if we want to use sand for our buildings
0:04:06 > 0:04:08and gravel for our gardens,
0:04:08 > 0:04:10we've got to get them from somewhere.