Thousands of miles separate northern Australia, southern South Africa and eastern Canada. There is also a vast distance between the Mexican Pacific Ocean and the Spanish Canary Islands, or between Southeast Asia and Suriname. However, their flora is more similar than nature dictates. It is the still visible trace of European colonialism.
A group of researchers overlapping the extension and duration of four major empires with the current distribution of Thousands of plant species. They verified that many regions share the landscape for decades and even centuries after those empires fell. It was the British who changed the environment the most, and the Dutch the least. Between them lie Spain (the second most transformed country in the world) and Portugal.
On their travels, humans always carried with them a part of the flora of their homeland. Whether it is for food, aesthetics, nostalgia, or simply by chance, the introduction of exotic species that end up adapting to the new environment is a constant in human history. But this transport grew on a previously unknown scale with the beginning of the era of colonial empires when Europeans, starting around 1492, began to connect all parts of the planet.
Experts in biological invasions used the latest information found in GloNAF, a global database containing the distribution of naturalized plants, to determine their presence in nearly 1,200 areas that were once colonies of one or more major cities. The results were published Monday in the scientific journal Nature’s environment and evolution.
As would be expected in empires as large and diverse as the four under study (Spanish, British, Dutch, and Portuguese), there is great variance in the landscape. The variable most affecting the diversity of vegetation in any location is the climate. But researchers soon noticed that when comparing different and distant regions belonging to the same empire, some had a greater degree of similarity than might be caused simply by climate, latitude, or random chance.
There are a series of explanations for this tendency to standardize within each empire, says Bernd Lenzner, a botanist at the University of Vienna (Austria) and lead author of the study. “One of them, which we consider important, is that the British Empire was, on the one hand, very long-standing, but also very recent.” In fact, in their analysis, they noted that the more an area belonged to an empire, the greater the botanical similarity was. Imperial longevity would also explain a lot of common landscapes in different regions of Former Spanish Empire. Some, such as various Mexican or Andean ecoregions, have belonged to the Spanish Crown for 290 years.
Every empire played a role, too. The Spanish Empire began expanding before the British did, and the expansion was done mainly on wooden ships. On the other hand, Britain expanded through steam-engine ships and trains, which facilitated communication between the various parts of British territory. In the sixteenth and seventeenth centuries, led by the Spaniards, there were no plans for the conscious introduction and naturalization of species from one place to another. It wasn’t until the eighteenth and nineteenth centuries, the golden age of British EmpireThese gardens and botanical societies became very popular, seeking to reproduce the English countryside in the colonies.
The style of governance for each empire was a relevant factor as well. The restrictive trade policies of the European empires ensured that plants were mostly traded between regions occupied by the same power. Therefore, the range of species exchanged between regions was limited to the territory of the Empire, and as a result, these regions became more similar in their flora than those found abroad,” notes Lenzner. Spain and Portugal, and to a lesser extent Britain, only allowed intra-imperial trade; everything else It was considered contraband. The state of the Dutch Empire, the least similar among its colonies, is indicative of the opposite relationship. The Netherlands maintained more open trade policies, which would have facilitated greater heterogeneity. However, there are important exceptions, such as the commercial introduction of production Rubber is in Southeast Asia, separated by thousands of kilometers and two oceans from what is now Suriname, the original home of the buckeye tree from which the natural latex is obtained.
“The restrictive trade policies of the European empires ensured that plants were mostly traded between regions occupied by the same power.”
Bernd Lenzner, botanist at the University of Vienna and expert in invasive species
The research also reveals that the central regions of each empire show greater similarity in their landscapes. In particular, regions of commercial importance, administrative capitals, and major ports show greater convergence of plants within each empire. This is the state of the current state coast of Guerrero, Baja California (Mexico) and Nariño (Colombia). In the British Empire, Eastern Australia and India stand out.
In the opposite direction, from the colonies to the city, researchers hardly noticed significant modifications in the landscapes of ancient empires, with the exception of a few exotic gardens (agricultural species were not included in the study). The exception would be the naturalization of various types of cacti, such as the prickly pear, which is now found in most of Spain and southern Italy. Franz Essell, also from the University of Vienna and the lead author of this research, said that the capital often served as a “centre for the propagation of exotic plants, because in many cases new species were introduced from colonies first to the mother country, and then they spread to other regions within Empire.”
Invasions of animals, such as rabbits in Australia, are well documented. But the influence of exotic plants can also be significant. “I agree that notorious cases of species well known to humans, such as rabbits, stand out for their harmful nature. But non-native plants can profoundly alter habitats and ecosystems,” notes Essell. One example is cat’s claw (Carpobrotus edulis). Originally from South Africa, “it has been introduced as an ornamental species in Mediterranean regions around the world, where it has become very abundant along coastlines and where it outperforms specialized native plant species,” he says. Essl also has a special mention of carrots. He and his colleagues showed in previous work that more than a quarter of the islands studied now contain more exotic plant species than native ones. A notable example is, for example, Hawaii or Mauritius, which many have depicted as an almost pure paradise. The scientist warns that “the exotic plant species there have severely altered the island’s ecosystems”.
One factor that exacerbates the impact of plant colonization is that plants are the basis of every ecosystem. Another is time. “We’ve learned that alien species can take decades to form and spread in an area they’ve been introduced to, and that this process often occurs with significant delays,” he recalls. But he adds: “The discovery of such legacies for several decades, sometimes even centuries, after the collapse of European empires is something to be reckoned with. This shows that we need to be very careful and aware of the species in which we move around the world.”
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