Invasive species


Britannica identifies the invasive species as follows: “Invasive species, also called introduced species, alien species, or exotic species, any nonnative species that significantly modifies or disrupts the ecosystems it colonizes.” The way a species arrives in a new environment can be done in numerous ways; either by natural migration or by activities of other species. Humans do it directly through pet trade or global commerce or indirectly by unintentional “hitchhiking” invaders in ships, planes, trucks, shipping containers or packing materials. Another reason for such a phenomenon is that a species can no longer adapt to the environmental conditions of their habitat. Therefore the invasive species may have more opportunities in an alternative future climate than they have at present.
Recently in Greece there have been many headlines about a species that swarmed the Korinthian Gulf- the tropical scyphozoan Rhopilema nomadica, a kind of Jellyfish. This particular species is listed as one of the “100 worst invading species” in the Alien Invasive Species Inventories for Europe (DAISIE 2009).
There are several reasons that an invasive species can flourish. But before blaming it for destroying our weekend by the beach, let’s get to know it better. Rhopilema nomadica known in english as Nomad Jellyfish, is native in East Africa and Red Sea but its known introduced range is Egypt, Israel, Lebanon, Turkey and Greece. Its natural predators are fish, like tuna, mackerel and marine turtles; apparently,overfishing these natural predators helps the species in question thrive. Spawning occurs between June and August and the sexually reproducing swimming scyphomedusae appears when the water temperature exceeds 24º C. It entered the Mediterranean through the Suez Canal in the late 70s and it first appeared in Greece in Lakonikos Gulf in 2006 (Siokou-Frangou et al. 2006). Nonetheless, several other factors could help or hinder the rise of Nomad jellyfishes. Temperature is directly correlated with the population of this particular species and wind traffic at sea affects them. They are offshore and with the help of currents produced by the wind gather up at beaches.
Cost is another important factor that should be considered regarding alien species. When the costs have become apparent, they can be vast; one study in the United States in 2001 estimated that costs associated with alien species amount to some US$136 billion per year and Canada in 2004, estimated that a preliminary review of alien species pegged them conservatively at $13,3 millions to $34,5 millions, annually, for 16 invasive species alone (Joanne Laucious, 2017). These costs must usually be covered by someone other than those who sponsored or promoted the introduction of the species, usually the general public. Decision-makers need to invest more in assessing the potential impacts before allowing potential introductions as well as incorporate more biosecurity measures once the species has been introduced (Jeff McNeely, 2001).
Yet, the nomad jellyfish is a minor incidence of invasion. The most memorable examples of invasive species are the kudzu plant from Japan, the cane toad from America, the asian tiger mosquito, zebra mussels from southern Russia, rats etc. People have always been on the move, carrying other species with them. Australian aborigines brought in the dingo, Polynesians sailed with pigs, and the Asians who first peopled the Americas brought dogs with them (Jeff McNeely, 2001). In the very end,the worst invasive species known to human, is human.

Mara Vasileiou for Arid Zone Afforestation


May, a crucial month across the planet.


For wild baby animals, this is the most critical time in their young lives right across the planet. May, is the “make or break” month. Lion cubs in Masai Mara dessert in Africa, black bears in Minnesota, macaque monkeys in Sri Lanka, meerkats in South Africa to the grey whales in the Pacific and their calves running the gauntlet of killer whales. All struggle for survival.
But is also spring time, a season that transforms and rejuvenates the earth and this is influencing the whole ecosystem. During this time of plenty, most animals are giving birth to be able to provide the best head start to their young ones with an abundance of food, either they are the prey or the predator. But safety is another chapter that most of the animals cannot guarantee to their offsprings.
Still realizing the connections through several organisms and how dependable are on each other, we can slightly comprehend how crucial is the survival of the next generation for several species and for the environment around us. And we still learning. A glorious example is this of the gray wolves in Yellowstone Park.
In Yellowstone Park, wolf cubs are emerging after 63 days of gestation, during late April – early May. Their survival is depending on the prey availability. And the whole ecosystem is depending on the survival of these cubs. Wolves were reintroduced in the Yellowstone Park in 1995, after their extinction on 1926 due to no legal protection for wildlife in the park . Since then, miraculous changes took place in the park. George Monbiot, is a British writer and an environmentalist. In THIS video he explains how and why is important to protect and respect the ‘home’ of our fellow creatures.

Good luck to them all.
Mara Vasileiou (Arid Zone Afforestation)