Invasive species take a toll on their surroundings. But that doesn’t mean that invaders are universally destructive. Ecosystems are dynamic, and once an invasive species arrives, it can develop intricate relationships with other organisms. Sometimes, an invader becomes an integral link in a delicate ecological web, complicating efforts to eradicate it.
One example lives in the salt marshes of Northern California. An aggressive species of cordgrass called Spartina alterniflora arrived in California in the 1970s and has taken hold in San Francisco Bay, hybridizing with a native species, Spartina foliosa. The invasive hybrid grows quickly, displacing native species and choking precious waterways. But it has also become a vital nesting and foraging habitat for the endangered California clapper rail. As soon as land managers began efforts to eradicate it, the local clapper rail population plummeted by nearly half.
It’s quite an ecological conundrum: eradicating the invasive Spartina hybrid puts the vulnerable clapper rail at risk, while leaving the invader alone would result in further damage to the marshes.