In an era pre-technology, a man who never set foot in India had the daring to dream of the ecology, the ecological history, of a land he had never seen. Although his aim seemed fantastical, he set about charting the biogeography of the Indian subcontinent with an enthusiasm that we researchers in India cannot seem to muster about our own country today.

Today, 14th September, is celebrated as Humboldt Day in honour of Alexander von Humboldt, bringing together ecologists, geologists, botanists, zoologists, taxonomists, paleontologists, and biogeographers (among others) with a series of discussions around the field of biogeography. Humboldt, fondly known as the “father of plant geography,” created the concept of isotherms, or regions of equal temperature across geographical features, allowing other scientists to connect climate and vegetation in a revolutionary discovery. Hence, we now know that there are specific patterns to life existing in different climate zones. The father of natural selection, Charles Darwin, himself refers to Humboldt’s work in his Voyage of the Beagle.

But what is biogeography, and why does it apply to us?

Biogeography is the study of the geographical distribution of plants and animals and the series of events that led to current species distributions. One of the most basic concepts of biogeography is that species that are closely related are often found in geographically-proximate areas. Just as the field of human geography looks at the patterns of migration of humans since the beginning of mankind, biogeography studies migration patterns in nature. Historical events such as speciation, continental drift, extinction, and glaciation rule species distribution patterns.

Island biogeography theory is perhaps the most brilliant nugget to have surfaced from the broader field of geography and biogeography. Islands are known to be the perfect microcosms to study large-scale patterns and processes observed globally. They are also ideal from the perspective of invasion ecology, as scientists can observe how invasive species enter island ecosystems and colonize and outcompete native (or preexisting) species. Given the wide range of island systems across the planet, it is easy to upscale to one’s study biome or ecosystem of interest. For example, a researcher interested in studying tropical forests could conduct research on a tropical island with similar climatic and biotic variables. Upscaling is an art that most researchers have mastered.

One of the co-authors of the seminal text “The Theory of Island Biogeography” is Edward O. Wilson (better known as E.O. Wilson, or the Antman). I was privileged enough to study my master’s education at Duke University’s Nicholas School of the Environment, where E.O. Wilson had his research base, and heard multiple lectures from him on this subject. To learn biogeography theory from the founder of the same is…well…surreal. From Wilson’s work sprung a new era of biogeography since the work of Watson and Wallace nearly a century prior.

Biogeography has applications in studying the spread of infectious diseases, much like the current COVID-19 pandemic. Drawing from different fields, it creates a series of pathways based on likely factors affecting the ability of a disease to spread from one geographical region to another. Humans have, of course, added to the complexity of modern biogeographical mapping, but the challenge only makes it more exciting. Other modern applications include conservation planning, invasion ecology, and species distribution modeling, and technology is playing an increasingly important role in handling the types of large-distance calculations and hypotheses that are typical of this field.

As a geologist and ecologist, I am immersed in biogeography. India, with its rich geographical diversity, high endemicity, and myriad biodiversity hotspots holds immense potential for biogeographical studies. Landscapes such as the Himalayas, the Western Ghats, and the Andaman and Nicobar Islands are living museums for paleoecology and biogeography. Their origins are tumultous, and they are simply bursting at the seams with ecological knowledge.

The issue is simply one of scale – most researchers focus on the scale of individual study sites or ecosystems, whereas biogeography requires an approach that spans countries, continents, or even the world.

Some resources to explore further: