Throughout the experiment, they measured the effects of each species mix on three important salt marsh functions: overall grass growth (productivity); the rate of dead plant removal (decomposition); and how fast tidal or storm surge water percolated through the marsh (filtration).
The effect of the species removals on individual functions varied considerably, because in salt marshes, each species is very good at performing one or two functions.
However, when all three key species were present, the average rate of all functions -- a measure of overall ecosystem health -- rose simultaneously.
"Our study provides a rare, real-world example that the loss of key species can have profound impacts on the overall performance of an ecosystem," Silliman said. "It suggests that the ability of nature to perform well at multiple levels may depend not just on the overall number of species present, but on having many distantly related species, each of which performs a particular task that keeps an ecosystem healthy and allows it to provide the multiple benefits humans value."
"If we had only been looking at three different species of similarly functioning crabs, or only one marsh function, we would have missed that, and erroneously predicted that only one consumer species is needed to maintain high system performance," he said.
|Contact: Tim Lucas|