Bob Butler's special series on the environmental tragedy of coastal Senegal is sad reading. But as someone with a bit of knowledge about geology, I have to point out that the coastal flooding, erosion of levees and apparent land subsidence is NOT caused by global warming or climate change. All of these things happen along the American coastline too--consider the Sacramento Delta and the Pacific shoreline for local examples--and the most important cause is unwise human activities. These include four major factors:

• Lowering the land surface by pumping groundwater, draining wetlands, mechanized agriculture, and deforestation that worsens erosion
• Interfering with the beach, most notoriously with jetties to build one beach at another's expense but also by damming rivers that supply the coast with sand
• Building too close to shore, then mounting defensive actions when the sea encroaches that make things worse
• Disturbing the seafloor by dredging, coral mining and similar actions that remove protection against large waves

I think it's unfortunate that Butler and his editor are so eager to call upon sea-level rise while sparing the Senegalese authorities any blame. Ignorance and short-sightedness are to blame. Every aspect of the Senegalese situation is sadly familiar from the American experience of the 20th century. Your able science reporter, Betsy Mason, will readily agree with these facts.

Andrew Alden