It’s always good to remind ourselves how little we know. Or perhaps more optimistically, how much we still have to find out. The neuroscientist David Eagleman likens knowledge to a pier jutting out into a vast ocean of mystery and possibilities. No matter how long the pier, the horizon never gets any nearer.
It’s remarkable how much we still don’t know about the animals, plants, fungi and the rest that share our tiny corner of what might as well be an infinite universe (assuming just the one universe). We don’t even know how many species of them there are. It might be 2m or 20m. We do know that we’ve formally described fewer than 2m of them. (But we don’t know how many fewer because we don’t know how many species have been mistakenly described more than once.)
Meanwhile, much more is known about some countries than others. Rich, northern countries have been more thoroughly surveyed than poor tropical ones, for instance. The upshot is that any attempt to answer this one is always going to be a bit back-of-the-envelope.
Since 2016, the environmental news organisation Mongabay has been giving it a good try by pulling together the data available for amphibians, birds, fish, mammals, reptiles and vascular plants (though it excludes invertebrates, which comprise the majority of animal species).
Which country is the most biodiverse?
It might not be much of a surprise, blessed as it is with more than its fair share of Amazon rainforest, that Brazil comes out top. About 18 per cent of all described bird species are found within its borders, as are 14 per cent of amphibians, 7 per cent of mammals, 14 per cent of reptiles, 12 per cent of fish and 13 per cent of plants.
Part of the reason is its size. All else being equal, big countries will tend to rank higher just because they have more space. And Brazil is huge. Covering 8.5m km² of the world’s surface, it is the fifth biggest of all countries. Indeed, rank countries in terms of species number per unit area and Brazil doesn’t make the top 10.
But size isn’t everything. The two biggest countries, Russia and Canada, don’t even make it into the top 50 for overall species numbers. Seven of the top 10 countries (nine out of 10 when country-size is taken into account) are located in the tropics.
It’s known that biodiversity increases towards the Equator. The reasons for that aren’t entirely clear but it might have something to do with the tropics having been spared the ice ages that have intermittently scoured the life from higher latitudes, and the year-round high temperatures speeding up biological processes, including the creation of new species. Whatever the explanation, the sheer diversity of life in the tropics is, like the view from the end of a pier, as humbling as it is inspiring.
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Main image: a biodiverse habitat by the sea. Credit: Getty