Understanding species survival requires deep ecological insight, without it, reintroductions become trial-and-error – and mostly error.

The successful reintroduction of species to old or new habitats requires an understanding of the ecological factors that help them thrive (positive ecology) and those that lead to decline (negative ecology).  In this talk, Hugh Loxdale MBE explores what drives survival—or extinction—in British birds and butterflies, drawing on over a century of detailed study. Despite long-term research, much about butterfly ecology remains a mystery, especially for species with unpredictable “boom and bust” cycles or those that resist reintroduction, even into seemingly ideal former habitats.

As Charles Darwin realised in his famous treatise, the Origin of Species (1859), extinction, brought about by a plethora of causes, including disease, inbreeding and competition of one sort or another, is a critical part of evolution. It proceeds by the process of ecological specialisation, as living organisms adapt to occupy vacant niches, either novel ones or those previously occupied. Certain species of living organism can persist for many millions of years, sometimes hardly changed morphologically and genetically (e.g. coelacanth), whereas others seemingly persist for relatively shorter timescales before they disappear from the face of the Earth. If conservationists are to successfully introduce species into new habitats or ones they formerly occupied, then it is essential that the positive ecology is understood, as well as those which lead to their extinction (negative ecology).