Would elephants really replace the woolly mammoth?

Rewilding involves restoring nature at large scales, typically by reintroducing species that have gone extinct and have had important interactions with other organisms.  It has received a lot of popular attention lately, helped in part by George Mobiot’s 2013 book Feral and its growing number of success stories.  But the idea of rewilding remains highly controversial, particularly when it involves adding apex predators like wolves into places with people.  One the reasons for the controversy is the lack of empirical data to assess the effectiveness of its outcomes.  Conservationists are often relying on a handful of well-known examples, such as from Yellowstone National Park.

 

In a new paper published last week in the Philosophical Transactions of the Royal Society B, we now summarise the numerical data around whether rewilding works and identify the biases in experimental study.  The paper is part of a special issue on rewilding, organised by Elisabeth Bakker and Jens-Christian Svenning, to which we were kindly asked to contribute towards.  And we were even interviewed in last week's issue of Science about the special issue and importance of trophic rewilding for the important task of keeping the Arctic cool.

Our new synthesis discovers that rewilding can measurably restore ecosystems, potentially over short timescales and even if different species to those that were lost are introduced.  Our approach involved surveying over 1000 published papers for cases where animals had been introduced to sites - whether intentionally or not - and then determining whether these introduces could fill the role of extinct species.  Not only did we find that rewilding impacted lower trophic levels, we also discovered similar responses of lower trophic levels to both intentional and unintentional rewilding, suggesting that we could use the unintentional cases to test theory about the factors that might influence rewilding using larger datasets than would otherwise be possible.  In doing so, we also highlight knowledge gaps that need closing to advance the evidence base for rewilding. Hopefully this information will be useful for large-scale initiatives, such as those supported by Rewilding Britain.