In Bayou Farewell, what are the key ecological and environmental contributors to the demise of the Cajun coast?

Bayou Farewell by Mike Tidwell details some of the changes affecting the bayous and Cajun culture in the twenty-first century from a participant observer perspective. Tidwell spent a year living and working with Cajun families on the southwestern coast of Louisiana and treats social and cultural issues by embedding them in an anecdotal framework so that the reader can see how issues affect individual people and families. The book was written before Hurricane Katrina and subsequent detailed scientific studies of the bayou ecosystem, but those studies do tend to observe and emphasize rather than contradict Tidwell's points.

The Cajuns were descended from a group of French people who settled the Maritime provinces of Canada ("Cajun" is a contraction of "Canadian") in the seventeenth century and were displaced by the British; many resettled in Louisiana, which was, at the time, a French possession. They developed a distinctive culture and language and cuisine, a unique musical tradition, and a life dependent on fishing. 

On a cultural level, Cajun life is threatened by there being better-paying and less physically arduous jobs available to young people than working on small fishing boats. The wide availability of the Internet, public schooling, and mass media have led to a precipitous decline in the use of French as a primary language. Thus younger generations of Cajuns are becoming increasingly Americanized.

On an environmental level, two anthropogenic factors have been destroying the bayous. The first is dredging and flood control on the Mississippi River which reduces the silt needed to replenish the bayou lands. The second is exploitation of oil in the Gulf of Mexico. Digging channels for pipelines and dredging to help the oil industry accelerated erosion. The Deepwater Horizon spill of 2010 and other lesser spills and leaks have contaminated fisheries. Hurricane Katrina destroyed wetlands.

Human-caused climate change, including rising sea levels, is the greatest threat to the bayous. NASA displays on its website satellite photos detailing the rapid destruction of the Louisiana wetlands. The Isle de Jean Charles band of the Biloxi-Chitimacha-Choctaw have, as of 2016, become the first designated climate change refugees in the United States, as their territory is being covered by the sea.