Terrestrial Ecosystems in Country and WDPA protected sites. Analysis performed by L. Battistella in February 2021. Original dataset provided by "USGS-TNC" (World Terrestrial Ecosystems, Sayre et al. 2020).

Diversity of terrestrial ecosystems in protected areas and countries expressed by Shannon index.

Shannon or Shannon--Weaver (or Shannon--Wiener) index is defined as $H = -sum p_i log(b) p_i$, where $p_i$ is the proportional abundance of species $i$ and $b$ is the base of the logarithm. It is most popular to use natural logarithms, but some argue for base $b = 2$ (which makes sense, but no real difference). 

Range: SHDI ≥ 0, without limit. SHDI = 0 when the landscape contains only 1 patch (i.e., no diversity). SHDI increases as the number of different patch types (i.e., patch richness) increases and/or the proportional distribution of area among patch types becomes more equitable.