Even with perfect information, which is rare even for the most well-known components of ecology for the most well-known species, we don't know for sure what will happen. W/ stochastic environmental conditions and species interactions, potential outcomes vary enormously
We wanted to know what the biggest risks were. What's the worst-case? Is the network of species likely to be stable? For what species might we be least confident of long term success? Are there interactions or orders that would reduce long-term success?
Figure 6: Proportion of models where reintroduction failed for six species across different reintroduction strategies (rows) and expert matrices (columns). Grey squares indicate proportions lower than 1%; crosses indicate species that were not reintroduced in that strategy.
The results were reassuring!!! Model results predict that almost all reintroductions will be successful (12.5 out of 13), regardless of choice of strategy.
Interestingly, we found that the worst-performing strategy was choosing not to reintroduce boodies, so perhaps the benefit provided by this ecosystem engineer outweighs the negative effect of competition, although there is uncertainty.
The approach identified which alternative strategies were good, bad or indifferent for each species and which species were consistently prone to success or failure, helping us to identify critical elements to be monitored more closely within the system.
We were also able to identify potential causes of failure. For dibblers (PC: Jason McDonnell) the strongest association with reintroduction failure was competition with other small mammals. In contrast, predation by Chuditch was relatively weak.
This means we can focus our attention on monitoring those components of the ecosystem that pose a potential risk (so competition for Dibblers).
Should we need to change our status quo recipe to one of the alternatives, this is likely to be okay, which means that the program can more confidently and flexibly respond to logistical constraints, environmental conditions and availability of animals.
It also means there is greater scope to accommodate other objectives, like information gain.
The ensemble ecosystem modelling approach is a really cool exercise in risk analysis! It helped ID options most likely to achieve the desired outcome and simplified a problem so complex it is beyond our capacity as humans to process all elements of the complexity.
AND... even better, now we have it all set up, it's pretty easy to update as information is gathered... so stay tuned for more in years to come as the introductions of all 8 mammals and one bird proceed!
Australia has tragically lost much of its mammal fauna from vast swathes of the burnt brown land. Over 10% of mammal fauna across the continent has disappeared into extinction, and many more remain only on islands: pnas.org/content/112/15…
Translocations are increasingly common, as we endeavour to restore some of the lost magic of those incredible creatures that hop and scurry across the landscape.