Physical Changes
Physical changes to the estuary can be summed up in one sentence. Siltation at the head of the estuary and erosion at it's mouth. 

The silting up of the estuary makes a fascinating human story. From the time of the Normans, who built a weir at Chester  to the building of the "New Cut" (canalisation of the River Dee) in 1737 man's interference has accelerated silting. Chester was lost as a port in the Middle Ages and all the small towns along the Wirral coast became ports in turn until they too silted up during the 19th century. One of these ports was Parkgate, now a look over the sea front reveals miles of marsh only covered by the sea during a few days a year at the highest spring tides. However, many people don't realise that it was only seventy years ago that the marsh reached Parkgate as it spread along the Wirral coast. The map below shows just how rapid the spread of the marsh has been during the 20th century resulting in the inevitable loss of mudflats to the birds of the estuary. This increase in the marsh is a result of both the continuation of natural siltation and  also Spartina cord grass, introduced in order to stabilise the marsh round Summers Steel works at Shotton. Now the marsh has reached beyond Heswall, still remembered as a sandy beach by many locals.     

Increase of the marsh on the Dee Estuary during 20th Century.

Perhaps the most obvious change to the estuary is the steady erosion of the clay cliffs between West Kirby and Heswall, almost crumbling away as you watch. These cliffs, laid down in the last ice age, suffer from both storm damage from waves and water running off the land during heavy rain. They have  receded between five and fifteen feet this century causing the Wirral Rangers constant problems trying to maintain the various footpaths descending to the beach. 

Another natural feature which has receded this century are the sand dunes which are found both along the North Wales coast at the Point of Ayr and the north Wirral coast. A photograph in one of the Dee Estuary Strategy newsletters shows the Point of Ayr lighthouse clearly in the middle of the sand dunes at the beginning of the century, now the sand dunes are over 100 yards away. The north Wirral coast suffered from regular inundations of the sea during the highest tides until a large concrete embankment was built in the latter half of the century.

The Birds
Wildfowl: Unlike most of the other major estuaries of the United kingdom the Dee does not have large numbers of geese, only the odd visiting small flock of  Pink-footed  or Brent Geese being seen. Early on in the century much larger flocks of Pink-footed Geese over wintered here. Unfortunately disturbance due to over shooting and a build up of industry between the two world wars led to the desertion of the Dee by the geese to South West Lancashire.

Unlike geese, duck have been a big success story. This has come about from the establishment of a network of reserves and no-shooting zones, the numbers also reflect the increase of duck in West Europe generally. The table below shows how the numbers of the main species of  duck have changed this century. 
 

	1920/1930	1950s	1960's	1970's	1980's	1990's
Teal	No data	No data	300	700	4000	5000
Pintail	300	3500	1000	2800	6500	5300
Shelduck	No data	No data	2000	4300	5600	7800

Waders: Accurate wader counts started in 1969 and the table below shows how the numbers have fluctuated since then. It is a complex picture but surely no coincidence that the species which dropped dramatically in the late '70s and '80's - Knot, Dunlin and Bar-tailed Godwit - are those that inhabit the mouth of the estuary where disturbance was particularly bad. Since then disturbance has been much reduced at  the  high tide roost at West Kirby (see next article below) and the Hilbre islands, where sea angling now seems to be far less a popular past time. 

It must be remembered that the counts shown below are taken from high tide roosts. They only tell part of the story as many of  the Knot and Bar-tailed Godwit which feed on the sand and mudflats leave the estuary at high tide to roost on the less disturbed Alt Estuary a few miles away. WeBS counts indicate that this is a pattern of feeding and roosting which has become much more widespread during the past 20 years.

 

	1969/75	1984/89	1993/98
Oystercatcher	14400	29500	24600
Knot	31200	17000	18500
Dunlin	30000	14500	25800
Black-Tailed Godwit	730	500	1800
Bar-Tailed Godwit	5000	<1000	1200
Curlew	3500	3400	4200
Redshank	5700	6900	6300

The numbers of birds shown in the tables above  are based on data from the following sources:
Wildfowl in Great Britain, The Wildfowl Trust, 1963.
Estuary Birds, A.J.Prater, 1981.
Wetland Bird Survey Counts between 1984 and 1999.