It has been hard to escape media reports of plummeting insect populations over recent years (so-called ‘insect Armageddon’). Of course, the picture is far more uncertain and nuanced than newspaper headlines suggest (shocker!). Nonetheless, there is solid evidence of worrying long-term declines in insect numbers for some parts of the world. This is extremely concerning, not least because insects are the glue that holds the natural world together.
For biodiversity loss globally, conservation groups have traditionally recognised five key threats: habitat change (ranging from its complete removal through to more subtle degradation effects), species overexploitation (fishing, hunting), invasive species and diseases, climate change, and pollution (which usually refers to chemicals, including pesticides and fertiliser).
But as often turns out to be the case, reality can be more complicated (or even quite different) to long-held conventional wisdom. Some potential causes of wildlife declines appear to have been overlooked historically, or at least, their impacts have gone largely unstudied.
One of these neglected areas is undoubtedly the consequences of the surge in artificial lighting.
Widespread extinctions and rapidly diminishing populations are probably what comes to mind when most of us think about the nature of biodiversity change in the 21st century.
This is not surprising. The influence of modern humans on the planet is vast. The growing demand for food, timber, and fuel increasingly erodes and degrades once pristine habitats. Decades of greenhouse gas emissions are causing global temperatures to steadily rise. Catastrophic weather events that used to be once-in-a-generation are becoming the new norm. The magnitude and rate of these changes have even led some scientists to propose a new geological epoch: the Anthropocene.
It is only to be expected that these accelerating impacts will be mirrored by plunging biodiversity trends. Some have estimated that species are being lost at more than one hundred times the natural rate. We may even be in the midst of the sixth mass extinction event.
But despite all this, the response of wildlife to human pressures is by no means universally negative.
This blog post is based on the introduction of an article I penned in September 2018for Atropos, an excellent magazine for British Lepidoptera and Odonata enthusiasts. It was published in issue 62 (2018).
Very hungry caterpillars
A caterpillar munching on a leaf is probably what comes to mind when most people picture the early life stages of butterflies and moths. But if Eric Carle’s classic is to be believed, caterpillars have a much more varied palette. It is certainly true that many species shun the conventional diet of leafy greens, even if lepidopterans that enjoy a diet of chocolate cake and Swiss cheese are confined to children’s storybooks.