Organisms have been moved around the world since the very beginning of life on Earth! But the scale of these movements was too limited to affect native species or their habitats because they moved in small numbers, over limited distances and slowly.
The spatial movement of (non-native) species follows the development of commercial intercontinental traffic, promoted by the dawn of the Age of Discovery and European colonialism.
Padrão dos Descobrimentos, Lisboa, Portugal
Source: Pixabay
If in the beginning, the sailing ships travels dependend on the wind patterns, with the advent of navigation systems and steam-powered ships, the number of possible pathways increased remarkably.
British steamer routes and large coaling stations as of 1899. Notice the number of connections between locations around the world that were established well before modern global trade and airplane transport developed.
Source: Lockwood JL, Hoopes MF, Marchetti MP (2007) Invasion Ecology. Blackwell Publishing, Oxford, UK, p. 35.
As you can imagine, with the rise of airplane transport, as well as people traveling around the world or demanding products, this human - assisted migrations of non-native species has increased dramatically.
In Western societies, from the great explorations until the early 20th century, non-native species were introduced elsewhere and considered ‘exotic’ curiosities, often viewed as a resource.
Many of this transported species were introduced as assets, with aesthetic and ornamental (plants and pets) purpose, or economic value.
But with time, some of those introductions became a threat to native species and ecosystems and for human well-being. Some of those became INVASIVE!
Charles Darwin was on of the first 19th century scientists mentioning invasive species in his writings. In The Origin of Species he described natives ‘conquered’ by introduced species (p. 69) and ‘yielding before advancing legions of plants and animals introduced from Europe’ (p. 164) and referred to ‘intruders’ (pp. 259, 314) having ‘invaded’ (p. 263) territories of other species. He also made important observations on the ecology of two species of thistles, both native to Europe, that were introduced in Argentina.
Some facts about invasive impacts:
- The introduction of the Nile perch (Lates niloticus) into Lake Victoria by authorities in the 1960s. This led to the disappearance of up to 200 native cichlid fish species, described by some scientists as “the greatest single paroxysm of extinction ever recorded”.
- The jelly fish or Leidy’s comb jelly (Mnemiopsis leidyi) caused a trophic-level disaster when it was introduced into the Black Sea in Europe from the Americas via ballast water. It began foraging on zooplankton and as it had no natural predators, lead to the collapse of anchovy farms and other fisheries on the Black Sea.
- Feral pigs (Sus scrofa) are an example of the damage which can be caused to island ecosystems by invasive species. They invaded pristine ecological sites in the Hawaiian islands, damaging native ecosystems by uprooting native plants and facilitating the spread of other introduced plant and bird species, including mosquitoes which carry avian diseases.
- Invasive rats are some of the largest contributors to seabird extinction and population declines globally. The 3 species of invasive rats, black rat (Rattus rattus) had the largest mean impact on seabirds followed by the Norway rat (R. norvegicus and ship rat (R. exulans)
Scopoli's shearwater (Calonectris diomedea) chick being attacked by a black rat
- The small Indian mongoose (Herpestes auropunctatus/ Herpestes javanicus) were introduced to many islands worldwide for control of rats and snakes, mainly in tropical areas, and also to islands in the Adriatic Sea. They are diurnal generalist carnivores that thrive in human-altered habitats, and which predation lead to the decline and extirpation of native mammals, birds, reptiles, and amphibians.
- Cheat grass (Bromus tectorum), a native of Eurasia, was first recognized in North America in 1889. It produces a litter that is slow to decompose and has drastically increased the frequency of fires in arid rangeland systems to a nearly annual cycle. This had lead to an almost complete loss of native woody species over large areas, and due to lack of cover and forage, songbirds and rodents abandon areas dominated by cheat grass.
- Bark stripping by gray squirrels (Sciurus carolinensis) on forestry production, and directly competing for habitat with the red squirrel (Sciurus vulgaris) in Britain and Italy.
Source: ISSG
Invasive species come with a huge monetary cost
In Europe the costs of invasive species can be estimated as €12.7 billion/year (source)
In the USA, it is estimated that damage and control cost of invasive species amounts to more than $138 billion/year (source)
Do you still want to bring living organisms as a souvenir from your travels?!
HOPE NOT!!
P.S. 1 - Did you find this matter of interest?
P.S. 2 - What can I do to improve my writing? Feel free to comment and upvote :)