When it comes to understanding why our planet’s biodiversity is declining so precipitously, no phrase has as much explanatory power as “shifting baselines” — as essayist Derrick Jensen put it, “[T]he process of becoming accustomed to, and accepting as normal, worsening conditions.” Every generation regards its own environment as natural and healthy, failing to recognize that the status quo is but a pale imitation of what previous generations enjoyed. The term was coined by Daniel Pauly, a fisheries biologist, and it’s most often applied to the collapse of global fisheries. Our oceans are plundered, but our lack of historical context prevents us from noticing.John Waldman is determined to wake us up to what we’ve lost. Waldman, a professor of biology at Queens College, is the author of Running Silver: Restoring Atlantic Rivers and Their Great Fish Migrations (Lyons Press, 2013), a book that not only elucidates the predicament of plummeting fisheries, but also provides a roadmap for escaping it. Waldman’s focus is diadromous fish — the migratory species, like salmon, sturgeon, eels, and shad, that once ran in great pulses up and down every East Coast river, providing sustenance for ecosystems and human communities. Centuries of dam construction, overfishing, and other deleterious forces have reduced these once-spectacular migrations to just a fraction of their historic abundance; yet thanks to our shifting baselines, we seem scarcely to have noticed, which only makes the problem worse. Waldman calls this phenomenon — in which species disappear from people’s awareness and so lose their advocates — “eco-social anomie.”Fortunately, the news for migratory fish is not all catastrophic. Waldman documents a number of heartening restoration efforts, especially dam removals, that are helping some species rebound, and proving that diadromous fish still have constituents. While the Atlantic Coast’s fish runs may never return to their former glory, there’s still time to restore their relevance to ecosystems and human lives. “Poor shad!” wrote Henry David Thoreau, to whom Waldman’s book is dedicated. “Where is thy redress?” Running Silver certainly isn’t complete redress for our troubled rivers, but it offers a guide to making amends. Learn more about your ad choices. Visit megaphone.fm/adchoices