Life in the Thames: Flora and Fauna of London’s River

The River Thames (346 km, Cotswolds → North Sea) is a recovery success story — declared biologically dead in 1957, now hosting 125 fish species, 300+ invertebrates, seals, porpoises, seahorses.

🌿 Flora

• Trees (banks): Willow (crack, white), poplar (black, Lombardy), alder, ash, oak, elm (Dutch elm disease survivors).
• Shrubs: Hawthorn, blackthorn, dogwood, elder, gorse, bramble.
• Marginal/emergent: Reed (Phragmites), sedge (Carex), rush (Juncus), yellow flag iris, purple loosestrife, water mint.
• Submerged: Potamogeton (pondweeds), Elodea, Myriophyllum, Callitriche.
• Algae: Diatoms, green (Chlorophyta), cyanobacteria (summer blooms).

🐟 Fauna

• Fish: Salmon (returning), sea trout, eel (critically endangered), flounder, bass, pike, perch, roach, bream, chub, barbel, gudgeon, smelt, lamprey (river/brook).
• Birds: Mute swan, Canada goose, mallard, tufted duck, cormorant, grey heron, little egret, kingfisher, sand martin, reed warbler, Cetti’s warbler.
• Mammals: Harbor seal (to Richmond), grey seal (estuary), harbour porpoise (tidal reach), otter (recolonizing), mink, water vole (reintroduced), bat species.
• Invertebrates: Crayfish (signal — invasive), Chinese mitten crab (invasive), freshwater mussels (depressed river mussel — rare), dragonflies (banded demoiselle), mayflies, caddisflies.

🎯 Indicator Species

Salmon, otter, seahorse, depressed river mussel = water quality improving. Chinese mitten crab, signal crayfish, pennywort = invasive pressure.

The Thames proves: even a "dead" urban river can revive with treatment, regulation, and time.