European colonial history has left its mark on nature around the world, according to a study that noted a greater similarity in the flora of foreign species in areas that were previously colonized than in other areas that were not.

The effects of this "biological invasion" are still visible today in the former colonies of the four major European empires, the Portuguese, Spanish, Dutch and British, according to the study published this week in the journal Nature Ecology and Evolution

Guillaume Latumbe, one of the study's lead authors, lecturer in biology on environmental changes at the University of Edinburgh, explained that "all the regions concerned had more homogeneous plant compositions than those in other regions that did not belong to colonial empires, but were located in the same geographical sector."

The researchers, led by Bernd Lenzens, of the Department of Botany and Biodiversity Research at the University of Vienna, compiled a database of about 1,200 regions in the world, including about 800 regions that were located in former empires. 

The researchers then interrupted this data with the GloNAF database, which currently includes more than 13,000 congener exotic plants in different regions of the world. They calculated the "Zeta" diversity index, which measures the degree of similarity, whether large or small, between geographical regions, in terms of their botanical composition.

The researchers concluded that the most important factors that lead to the continuation of the plant effects of certain empires on several regions are the duration of the continuation of colonization and its economic or strategic importance.