Take a journey from Liverpool, at whose University some of the seminal research on Welsh rivers was done fifty years ago, to the tip of western Wales where the headlands of south Pembrokeshire meet the swells of the Irish Sea, and you may pass over a range of Welsh freshwater environments. You will cross the Dee, whose tributary waters, ponded in the artificial Llyn Celyn, supply the north-west with drinking water and the Welsh with an understandable anger for valleys and villages forcibly flooded. You may divert towards the streams of mid-Wales, where the acidifying gases of the English Midlands’ industry still have their legacy in reduced diversity of invertebrates and fishes. Perhaps you will reflect, with the American ecologist, Aldo Leopold, that an ecologist lives in a world of wounds... the doctor who sees the marks of death in a community that believes itself well and does not want to be told otherwise.
But eventually you will pass into the wonderful, still-intact floodplains of the Tywi, commanded by the castle of Dryslwyn on its island in the middle, or, by another route, the Teifi upstream of Cardigan; you may reach the enchanting ash-clothed reaches of the Gwaun as it falls from the Preseli Hills into lower Fishguard, and drink your pint drawn from the barrel on the table in the pub at Pontfaen. Perhaps you will walk from Haverfordwest along the Cleddau and see the compass-net fishermen patiently waiting for the salmon. And if you are heedless, as once I was in taking my dog on a hike to see if it was possible to reach Pembroke without crossing a road, you may go thigh-deep in soft estuarine clay stained by the activities of those countless bacteria that make our world go round. At Pembroke you will see, on the Commons, a stream subjected to the worst horrors of drainage engineering, but you must see it as potential for enlightened future restoration if the EU Water Framework Directive is ever allowed to emerge as the revolutionary legislation that it could be.
When it comes to freshwaters, the Celts have the best of it. There are, of course, the Cumbrian Lake District and other gems in England, but the most part is a fair old mess of straightened channels, banished floodplains, and flows made brown in winter by eroded soil and green in summer by profligate nutrients. Even the Welsh uplands have not entirely escaped. Not for centuries have there been any truly pristine systems. The intricate roles of brown bears, salmon, nutrients, and woody debris that have been uncovered in the rivers of North America and Russia must also have been enacted here, but now are gone. Nonetheless, the best of what is left is still widespread, attractive and interesting, and enticingly accounted in this book. It has the great merit of being immediately understandable by a readership beyond freshwater biologists, is beautifully designed and illustrated, and could be a textbook of freshwater ecology as easily as books so intended. A sense of place is essential to a profound understanding of ecology and that sense is strong here. The editors and authors are to be congratulated on a contribution as welcome in its chosen mode as that of Dylan Thomas in his. For it is to the sloeblack, slow, black, crowblack, fishing-boat- bobbing sea that all the rivers flow.

Brian Moss
University of Liverpool