Are chalk streams rare?

2019-12-27 by No Comments

Are chalk streams rare?

Chalk streams are a characteristic and attractive feature of the Chilterns landscape. They are also a globally rare habitat, confined to north west Europe and to the UK in particular. In fact more than 85% of all the chalk streams in the world, are found in England.

Why are chalk streams rare?

About England’s chalk streams Our chalk streams are unique – with most found in southern England (and a few in France). But a combination of population growth, a spiralling increase in water use and pollution have put huge pressure on our rivers and streams.

Are all chalk streams SSSI?

Only a handful of chalk streams are given special protections – the Itchen, the Avon, the Lambourn and the Wensum are designated as international Special Areas of Conservation (SACs), and a further eight are designated as nationally important Sites of Special Scientific Interest (SSSIs).

What lives in chalk streams?

The chalk streams hold a good number of wild salmonid fish species such as the brown trout (Salmo trutta), Atlantic salmon (Salmo salar) and grayling (Thymallus thymallus). In addition to these there are also considerable numbers of stocked brown trout and stocked rainbow trout (Oncorhynchus mykiss).

How do chalk streams work?

Chalk streams are fed from groundwater held in the chalk that makes up the Chiltern Hills, and this gives them some unusual features. Chalk is an aquifer, which means that it is able to soak up and hold water – a bit like a sponge. Water can move through the chalk in cracks called fissures.

How many chalk streams are in the Chilterns?

300 chalk streams
There are only 300 chalk streams in the world and the Chilterns is home to 9 of these which are precious habitats that support some of the UK’s most endangered species such as the water vole, reed bunting and brown trout.

Why are chalk streams so biodiverse?

Chalk rivers emerge from the chalk aquifer, so the very pure water is rich in minerals and remains at a fairly constant temperature year-round. This lets diverse aquatic plants grow, including various species of water-crowfoot and water star-wort.

Why are chalk rivers in need of conservation?

Chalk streams represent important riverine habitats, due to unique physical characteristics which allow the slow passage of water through calcareous rock from groundwater aquifers, producing clear, nutrient-rich water of good chemical quality, characterised by stable flow, pH range (7.4-8.0), temperature regimes and …

Why do chalk streams support so many animals and plants?

Chalk rivers emerge from the chalk aquifer, so the very pure water is rich in minerals and remains at a fairly constant temperature year-round. The plant diversity and good water quality supports many invertebrate and fish species.

How many chalk streams are in the UK?

Geographers say there are only 210 true chalk streams anywhere in the world, and 160 of them are in England. You can find them draining chalk hills from the River Hull in Yorkshire, through the Chilterns and North and South Downs to the Piddle in Dorset.

How does a chalk stream work?

Are there any chalk streams in Kent?

In Kent the rivers Dour and Nailbourne are both chalk streams. Elham Valley is a chalk valley that has been created by the river Nailbourne and is located in Kent’s North Downs AONB.