Centuries of Human-Driven Change in Salt Marsh Ecosystems

Abstract

Salt marshes are among the most abundant, fertile, and accessible coastal habitats on earth, and they provide more ecosystem services to coastal populations than any other environment. Since the Middle Ages, humans have manipulated salt marshes at a grand scale, altering species composition, distribution, and ecosystem function. Here, we review historic and contemporary human activities in marsh ecosystems-exploitation of plant products; conversion to farmland, salt works, and urban land; introduction of non-native species; alteration of coastal hydrology; and metal and nutrient pollution. Unexpectedly, diverse types of impacts can have a similar consequence, turning salt marsh food webs upside down, dramatically increasing top down control. Of the various impacts, invasive species, runaway consumer effects, and sea level rise represent the greatest threats to salt marsh ecosystems. We conclude that the best way to protect salt marshes and the services they provide is through the integrated approach of ecosystem-based management.

Understanding and predicting wave erosion of marsh edges

“…Much attention has been devoted to the understanding and description of the processes which lead to observed equilibria in the vertical direction, or lack thereof, producing a rather comprehensive understanding of the controlling biological and physical processes [Allen, 1990;Morris et al, 2002;D'Alpaos et al, 2007;Kirwan and Murray, 2007;Marani et al, 2007;Mudd et al, 2009;Marani et al, 2010]. On the contrary, "lateral" evolution mechanisms have received comparatively much less attention, even though marsh degradation associated with edge erosion is arguably the chief mechanism by which marshes in coastal areas worldwide are being lost [Schwimmer, 2001;Gedan et al, 2009;van de Koppel et al, 2005;Mariotti and Fagherazzi, 2010]. Briefly, the current process understanding relates the erosion of a cliffed marsh edge (see Figure 1) to the fluctuating forces exerted on the margin by wave impact, which produces the removal of the bank material.…”

Biology in the Anthropocene: Challenges and insights from young fossil records

“…However, many other human pressures-most particularly nutrification, habitat conversion, and the overexploitation and introduction of species-also intensified with the expansion of human populations and technology during the Industrial Revolution and the post-World War II "Great Acceleration" (2,4,17,18) and are equally relevant to conservation and restoration efforts, as well as to basic ecological research. These pressures, moreover, started much earlier during preceding centuries to millennia at regional scales, both on land and in coastal seas, and have been accompanied by biological-stress syndromes (19), such as decreased body size, population size, trophic levels, and diversity, as well as functional and complete extinction of species (14,(20)(21)(22)(23)(24). These nonclimate factors are now as global as climate change (Fig.…”

The significance and vulnerability of Australian saltmarshes: implications for management in a changing climate

“…Recent research from the USA highlights the role of molluscs in saltmarsh die-off by selectively consuming saltmarsh vegetation (Gedan et al 2009); however, the role of herbivorous molluscs as habitat modifiers and top-down consumers has not been observed in Australia, but requires further attention. Mollusc adults and larvae are also prey for a range of estuarine predators, including eels, crabs, fish, waterbirds and mammals (Hollingsworth and Connolly 2006;Mazumder et al 2006;Roach 1998); these molluscs and other invertebrates appear to make an important contribution to the diet of fish feeding in saltmarsh (Mazumder et al 2006).…”