The phrase "breed like rabbits" does have a basis in biological fact: Rabbits are pretty good at reaching sexual maturity quickly and producing a lot of offspring. That’s why the little critters can create big problems when they reach a land where they weren’t meant to be. Rabbits, though cute, are some of the world’s worst invasive species.

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But new research shows that rabbits' vegetation-munching ways aren’t the only way these mammals alter ecosystems. Even 20 years after the bunny menace was eradicated from one island, differences persist in communities of soil fungi, Sarah Zielinkski reports for Science News.

The Kerguelen Islands in the far southern Indian Ocean aren’t a pleasant place to live. Temperatures rarely climb above 50 degrees Farenheit even in the summer. "It rains, snows or sleets for 300 days a year," Zielinkski writes. "And sustained winds of 150 kilometers per hour (93 mph) are not uncommon." Yet the French-claimed islands were were once stopping off points for whaling and seal-hunting ships. In an effort to make stays a little more pleasant, some sailors let European rabbits roam free, probably to create stock for future meals.

Researchers recently studied three islands to record the effects of rabbit invasion. The island of Grande Terre has many rabbits, while Ile Guillou’s rabbits were eradicated in 1994, and Ile Australia never had to contend with the beasties at all. In areas were rabbits thrived (and they did, without predators) native plant diversity declined and burrows made the land susceptible to erosion. In particular the researchers noted that soil fungi were very different on the two islands that had or have rabbits. Even 20 years after the rabbits left, Ile Guillou’s plant and fungal communities resembled that of Grande Terre.

The team published their findings in the journal Biology Letters.

The long-lasting effects could have come from disturbance of the soil through burrowing, rather than any specific rabbit-additions such as feces. A different disturbed soil site on Ile Australia showed some similarity to the soil fungal communities on the rabbit-affected islands. Native plants might be slow to grow back after such disturbance.

However, the study does point out that some subtle effects of an invasive species can persist for a long time after the problem animal or plant is gone. Helping an ecosystem recover from such a change may be trickier than previously thought.

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