Not only people, but also flora and fauna species tend to perform some sort of great migrations. Actually the plants that are considered immovable with their roots are the greatest travelers. Just think of tomatoes and potatoes with their American origin that are widespread across the globe now. However, those travels around the globe of plants hide certain dangers for the balance of world flora. Some of them manage to reach a state of peaceful co-existence with local species, but others tend to act like conquerors, pushing away from the ecosystem its typical inhabitants. That is why scientists refer to such species as  invasive ones, or weeds,for those that get into a battle with crops. Amaranth for instance, the terror for these lands, is a South American invader.

Associate Prof. Rossen Tsonev from the Ecology and Environmental Protection Department with the Sofia University claims that the most widespread weeds nowadays are a legacy from the time of the great migration of peoples:

“A large number of annual weeds originate from the semiarid areas of Central Asia with the great migration of peoples,” he says. “Hence their life of one year only, because they come from such semiarid places. They face similar conditions in our farmlands and vegetable gardens, plus the advantage of this rich soil and lots of water. So, they invade…”

Scientists say that ancient weeds that have reached some balance with local nature and people are less dangerous than the newcomers. And those are numerous and their number is constantly on the rise, the expert says with concern, giving several examples:

“The American wild pumpkin is such a species. Fishermen who visit the lower segments of the Iskar River know that the trees there, willows and poplars, are wrapped with  liana that strongly resembles a pumpkin species. It originates from North America and can cover a tree within a year only. There is another American weed with the lying name of ambrosia that penetrates our lands from northwest and has been transferred to Europe with crop seeds. It resembles a bit our mugwort, but the worst thing is that it causes hay fever.”

However, Amorpha is the main enemy of environmentalists in Bulgaria – a beautiful bush from the parks that has invaded the banks of the big rivers. This North American guest means death to poplar trees along the rivers.

“Its invasion is really visible along the lower segments of the Danube, where the climate is warmer – in Serbia, Romania and Bulgaria. Austria for instance doesn’t have such a problem. A large number of invasive species, mainly from North America or East Asia have been conquering over the past years forests along rivers that are new, pioneering ones, appearing and disappearing quickly. Hence their susceptibility.”

Of course, Bulgarian plants can also turn into invaders, Associate Prof. Tsonev says and adds:

“A beautiful European cornflower is among the most evil and dangerous weeds in North America. At the same time the rare and endangered species of Lindernia has become a curse for Chinese paddies. Only one field has remained active in Bulgaria, because a North American Lindernia has conquered the banks of the rivers and lakes, where it usually grows.”

Due to this complicated situation and the fight with invaders that can’t be chemical, for instance, a book is being prepared by scientists on the issue, as prevention seems to be the best alternative, according to Associate Prof. Tsonev. 

English version: Zhivko Stanchev