The challenge

The Aegean Sea and the Cycladic archipelago are parts of a Mediterranean biodiversity hotspot. Home to thousands of unique plant and animal species, many of which presently survive only on small islets, free of human habitation, the Cyclades are the last refuge for numerous threatened organisms. 

A further threat is the presence of rabbits on these islands who are now considered to be ‘invasive species’ due to the damaging effect they have had on indigenous and endangered plant species there. In contrast to larger islands that can sustain a greater variety of plant biodiversity, small islands that lack native herbivores harbour important and endemic plant species that are highly susceptible to invasive herbivores like rabbits.

The solution 

The solution, brainstormed in collaboration with the University of Michigan, has been to closely investigate and monitor the effects of invasive rabbits on the biodiversity of Cycladic islets, and to compile a bank of data to lay a foundation for managing the problem that has arisen.

What does the project deliver in practice?

The University’s team, led by Mr Johannes Foufopoulos, is assessing the situation on the ground to develop appropriate measures to protect these last wild arks of biodiversity in the Cyclades. 

Over the summer of 2022 Angelina Kossoff (a second-year Master’s student at the University of Michigan School for Environment and Sustainability), with the help of several research assistants, visited and quantified the ecological impacts of invasive European rabbits (Oryctolagus cuniculus) in the Cyclades.

METHODS

The University of Michigan team travelled to twelve islands in the Cyclades and compared ecological characteristics from: 1. Grazed islands (i.e. islands with present-day rabbit populations); 2. Ungrazed islands (intact islands free of rabbits), and, 3. Post-rabbit islands (islands with past, but now extirpated, rabbit populations). By comparing plant and insect biodiversity, soil samples etc. The team assessed impacts of invasive rabbits, as well as the potential for island recovery after rabbits are gone.

PRELIMINARY RESULTS

The UM team found that rabbits have been released on numerous uninhabited Cycladic islands for the purpose of hunting. Preliminary data indicates that these releases (rather than adding to the indigenous ecosystem) have a devastating impact on island vegetation and especially on the small herbaceous and annual plant species. 

However, our research reveals that the most damaging effect comes from the rabbits’ digging habits, which loosen the scarce soil and lead to massive wind erosion, therefore causing progressive desertification and undermining the long-term ability of islands to recover. 

In line with this, we discovered that islands on which rabbits had died-out (because they had eaten themselves out of existence), were in even worse shape than islands occupied by rabbits at present. This indicates a very low capacity for recovery once the soil is gone, and strongly suggests that to protect island ecosystems, rabbits need to be removed as soon as possible to prevent permanent damage.