Silliman, B. R., E. D. Grosholz, and M. D. Bertness (ed.) Human Impacts on Salt Marshes: A Global Perspective

“The state of our marshes is not good!” claim BrianSilliman, Edwin Grosholz, and Mark Bertness at the end oftheir edited book Human impacts on salt marshes: A globalperspective. As I sit here writing this review, I can look outmy window and see some of the expansive North Inlet saltmarsh and I am skeptical. The cordgrass is growing wellthis year, perhaps helped along by the freshwater dumpedfrom the regular summer thunderstorms that have playedhavoc with my field work. Water column nutrient concen-trations are again low, which is usual for this well-flushed,ocean-dominated system. My vertebrate-loving colleaguestell me that there are plenty of fish (and dolphins, andsharks) in the tidal creeks. Everything is as it should be. Butwait! Is that a small dieback area over there? And I think Isee some Phragmites at the edge of the marsh. Are thoseperiwinkles just hanging out or are they secretly plotting tomow down the entire marsh? Such is the paranoia that cangrip a fellow after reading through nearly 400 pagesdocumenting a suite of anthropogenic stressors that directlyor indirectly affect salt marshes.The basic objectives for the Human impacts on saltmarshes book are to: 1) summarize the causes andconsequences of anthropogenic impacts on salt marshes,both in North America and abroad, and 2) integrate thisinformation and provide it to coastal managers to allow themto combat a range of threats and promote cohesive marshconservationefforts.Thiseditedvolumecontains18chapters(plus introductory and concluding text by the editors) by atotal of 41 authors, almost a quarter of whom are locatedoutsidetheUnitedStates.Whilemuchofthebookfocusesonlessons learned from research in North American saltmarshes, the international authorship helps provide the“global perspective” mentioned in the book’s subtitle.The first part of the book covers Invasions in NorthAmerican Salt Marshes. The global invasion ofSpartinaspp., with an emphasis on invasions along the Pacificcoast of North America, is documented in Chapters 1and 2. Chapter 3 discusses several examples of invasiveanimals and their impacts on salt marshes, while the fourthchapter provides a long-term perspective on native vs.invasive Phragmites australis in eastern North Americanmarshes.The second partofthe bookdeals with Human InputsandConsumer Effects and includes chapters on goose over-grazing in Arctic marshes (Ch. 5), periwinkle grazing andfungal farming in southern U.S. marshes (Ch. 6), and ahypothesized alligator-nutria-plant trophic cascade inmarshes on the U.S. Gulf of Mexico coast (Ch. 7). Thesechapters provide compelling evidence that there are timesand situations when top-down control can limit primaryproduction and affect ecosystem structure and function. Ithink that Keddy and coauthors have it right in Ch. 7 whenthey suggest that salt marshes are controlled by a combina-tion of both top-down and bottom-up factors. There is justtoo much evidence for both modes of ecosystem regulationto believe that salt marsh food webs are exclusively top-down or exclusively bottom-up regulated.Land Use and Climate Change are covered in the thirdpart of the book. Two chapters use New England marshesas a case study on the effects of shoreline development(Ch. 8) and tidal restrictions and ditching (Ch. 9) onthe biological and physical properties of salt marshes.Chapter 10 is a wide-ranging chapter that covers marsh