Resilience or catastrophe?
From a conservation perspective, the change in western monarch
butterflies presents a conundrum. Even knowing how to implement the
precautionary principle of “Do no harm” is not obvious. On one hand,
the benefits of milkweed in urban gardens – to public outreach and
potentially to the monarch population – are large. On the other hand –
if diseased monarchs from urban gardens significantly reduce the
likelihood of a robust migration – then there might be real harm.
On the positive side, the appearance of this urban population is a
promising sign of how resilient the species might be. In northern
California, monarch butterflies have reinvented themselves. To residents
of coastal California cities, it must seem like a success to be seeing
monarch butterflies in their gardens on a regular basis. It is likely –
though not guaranteed – that western monarchs will persist in a small
portion of their historic range, even if they are lost from most of it.
And yet even this positive note is tinged by the knowledge that we are
losing something incredible. The overwintering clusters that used to
occur in California are a spectacular phenomenon, and we may completely
lose monarch butterflies from the interior West.
Perhaps the most striking feature of these changes is how quickly they
happened. It has only been about five years since we (Schultz et al.
2017) published our first analyses of declines in overwintering
populations of migratory monarch butterflies in the West. The subsequent
drops by two more orders or magnitude happened in less than three years.
By the time we resolve enough uncertainty to provide clear management
guidelines, the system may have shifted again. When Doak et al. (2008)
concluded that surprises are common in ecology, most of the examples
they pointed to were small-scale surprises in experiments, and often on
time scales that aligned much more with the time scales of research or
management. One lesson from western monarchs is that, in this rapidly
changing world, we should expect some species to change quickly and in
completely unexpected ways.