“Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare?”

“In considering the distribution of organic beings over the face of the globe, the first great fact which strikes us is, that neither the similarity nor the dissimilarity of the inhabitants of various regions can be accounted for by their climatal and other physical conditions.” Charles Darwin, 1859.

Was Darwin right?

Are the reasons why species live where they do and not in other places impenetrable mysteries; or are there patterns in the distribution of species that we can measure and explain?

This fascinating question has puzzled curious naturalists for many years, but answering it has become increasingly urgent in our current times of climate change. Describing the distribution of species between continents, Darwin correctly rules out climate as an important factor in determining species’ distributions, but within a continent most ecologists now believe climate to the dominant factor affecting large scale distributions. And if this is so, then climate change is likely to result in a dramatic redistribution of species with unknown consequences for the ecosystems that we all rely upon for survival. Some changes in distribution have already occurred, but if we can answer Darwin’s question we will have an important tool to predict the impacts of climate change and, most importantly, to act to reduce this impact.

Colin Beale
Spatial Ecologist