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  • Writer's pictureJose Arrieta

The World's Most Biodiverse Country per sq. km

I am Costa Rican. We are a proud people. One of the first things we learn is that ours is the most biodiverse country in the world. Yet, no one takes care of showing us that.

Biodiversity is a well-studied research field. New species are found every year but it takes a while until they are discovered and classified. What's more, there is a good log of which species live in which countries. At least for the level of detail, I care for in this post.

Here you can find the number of species of birds, amphibians, reptiles, fish, mammals, and vascular plants per country. They do not have all countries though.

If we plot the number of species per country versus the number of species per square kilometer (find the country areas here) we see this very heteroscedastic graph. Note that the plot below is a log-log plot. That is why the axes look weird. I do this so that the data is easier to analyze.

Biodiversity density vs number of species in total

Turns out my teachers were wrong. Brunei is the most biodiverse country in the world. It has 7076 species in its 5765 sq. km. That is 1.23 species per sq. km, about five times more than Costa Rica's still impressive 0.29 species per sq. km. What's most impressive is that Brunei is has a biodiversity density over 2300 higher than Canada, the country with the lowest biodiversity density.

To avoid being wrong, let's say that we just care for countries with over ten thousand square kilometers. In that case, Costa Rica is back on top.

Note: There is a more up-to-date way of measuring biodiversity (here). With this measure, Costa Rica is even lower, in the fifth position. Still, Costa Rica is the top country as long as we now consider countries with twelve thousand sq. km. It gets harder to keep the charade. Puh!

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