Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions

Hansen, D.M.; Donlan, C.J., Griffiths, C.J. & Campbell, K.J.
Ecography April 2010 Volume 33 Issue 2 pg 272-284

Using the label ‘forward-thinking restoration’ Hansen et al. argue that IUCN guidelines for species introductions should broaden to allow the introduction of extant (but non-native) megafauna to restore ecosystem function previously provided by now-extinct species. As an example, they argue for reintroduction of large tortoises to several island communities. Thirty-six species of large and giant tortoises have gone extinct since the Pleistocene, likely because of human activity. Because tortoises are key herbivores and seed dispersers, Hansen et al. suggest that introducing extant species would be an effective yet low-risk way to restore historic ecosystem processes.

The paper provides a compelling example of a generally extreme concept of “Pleistocene re-wilding.” By suggesting that we reconstruct some very historic processes, the paper forces consideration of both what and when do we restore to. The authors highlight that most tortoises extinctions were human-caused, implying that their goal is to reverse the effects of people on ecosystems. As a general goal this is unfeasible (we don’t know all the effects humans have had on ecosystems, and we couldn’t reverse them all anyway). Moreover, the authors emphasize the need to restore key processes. If process is what we value, why the tortoise went extinct is important only insofar as we can make sure it doesn’t happen again. Importantly, the paper also skims over the unintended consequences that could result from introducing key herbivores into systems that have been without them since the Pleistocene.