The river is "a particularly fine example of a lowland river on clay" according to its Sites of Special Scientific Interest citation. The SSSI was notified in 1989, and includes a 24-mile (39 km) stretch of the river from near its source to the point it joins the River Tame.[2] The Blythe has a wide range of natural geographical features such as riffles, pools, small cliffs and meanders, combined with a high diversity of substrate types ranging from fine silt and clay in the lower reaches to sands and gravels in the upper and middle reaches. The structure of this river is very variable and diverse, and is important as a rare example of such in lowland Britain.[2]
The diverse physical features of the Blythe are matched by its diverse plant communities. Botanically, the Blythe is one of the richest rivers in lowland England, with the most species-rich sections containing as many species as the very richest chalk streams.[2] In addition, several damp, unimproved meadows occur along the length of the river; they receive some of their water from annual flooding and are largely dependent upon the river for the maintenance of a high water-table.[2] As well as the rich and diverse flora, the river supports a diverse invertebrate community with a wide range of molluscs, oligochaetes and caddisflies.[2]
However, physical modification to the watercourse and the riparian zone has impacted the functionality of the River Blythe, resulting in the SSSI's condition labelled as "unfavourable no change" in 2017. [1] The factors leading to this were mainly due to historic management; many sections of the river have been straightened, and the riparian zone modified and disrupted, upsetting the site's ecological health and lowering the overall SSSI status.
The river is popular with anglers along much of its length, although in dry weather it can become shallow in places. Species to be found include perch, chub and dace with occasional summer carp being caught. The river also holds tench, bream and rudd and more recently a small number of barbel have been caught.