The world’s superpowers have long had their eyes on the Arctic. Donald Trump’s idea to buy Greenland from Denmark (which electrified global media) was not at all new. A similar offer was made already in 1946. During WWII, American troops protected Greenland’s deposits of cryolite – a rare mineral crucial for the war effort – against the Germans. Throughout the period, they treated the island as their sphere of influence. For the Chinese, the gateway to the Arctic is Island, which has become China’s hub for business and investment. In 2007, a Russian submarine planted a national flag on the seabed at the North Pole and five years later the Russian military launched a series of trainings to prepare the troops for military activity in polar regions.

The melting of sea ice, however, is making the far north more accessible not just for geopolitical players. Overshadowed by intense competition over military spheres of influence, valuable resources or shipping lanes, a very different invasion is now in full swing. And while it is rather quiet and inconspicuous, it is just as serious and potentially fraught with consequences. It is the invasion of alien species. What are they, where do they come from and are they really a reason to worry?

Exotic, alien or harmful?

Some claim that the term “invasive” should apply to all species not native to a given ecosystem, whether or not they came from faraway lands. According to this interpretation, examples of invasive species include the potato (brought to Europe from America in the 16^th century) and the Homo Sapiens (who – being native to the African savannah – began his highly successful invasion of foreign continents about 100 000 years ago). More commonly, though, the term is used to refer to those kinds of living organisms which spread rapidly in the new environment, altering the habitat, disturbing the natural balance and endangering native species (which still, come to think of it, fits the Homo Sapiens pretty well). The invaders are not only vertebrate animals or vascular plants, but also insects, crustaceans, fungi or even eggs and seeds.

Which way to the promised land?

Some invasive species have become such a common sight that we find it hard to believe they had actually arrived from afar. The already-mentioned potato, brought to Europe by Spanish explorers, was initially no more than a botanical curiosity and a source of pretty yellow flowers to adorn the outfits of Marie Antoinette. Nobody expected the plant would become a game-changer for Europe, freeing it to a significant degree from recurring mass famines. Not all introductions of alien species, however, come with a happy ending. Let’s take, for instance, the cane toad, brought to Australia in 1935. The toad was supposed to help deal with a beetle that wrought havoc in sugar cane plantations, but it soon became clear that the life cycles of the two species (which nobody saw fit to compare in advance) were too mismatched for the idea to work. As a result, the toad never even met its intended prey, but it did prove highly efficient in driving away other native species and – if this wasn’t bad enough – turned out to be poisonous.

The red-eared slider, which first made it to Poland as a pet, is gradually outcompeting the Polish pond turtle. American minks which escaped from Polish fur farms are decimating native bird populations. Sosnowsky's hogweed, an invasive weed species (also known as „Stalin’s revenge”) which was brought to Poland from the Caucasus at the end of the 1950s as superb cattle feed, has been a major headache ever since. The plant is not only hard to eradicate, but also dangerous, as physical contact with any of its parts causes serious skin burns.

Invasive organisms are often stowaways, covering thousands of kilometres amidst imported produce or even firewood. Like the gorgeous emerald ash borer, which made it from Asia to North America, where it lays waste to the local population of ash trees.

A conquest or a fresh start?

Why are invasive species seen as a problem? Because their ability to thrive and spread in new environments poses a serious threat to biological diversity, second only to habitat loss.

The key feature shared by most invasive species is their high ecological tolerance, or – to put it simply – opportunism. The species are not particularly specialized and easily adapt to new conditions, temperature, humidity and food resources. Being master breeders, they fill ecological niches and displace native species, which they hunt or – more commonly – outdo in the struggle for key resources. In extreme cases, they end up altering environmental conditions. What makes such invasions even more successful is the fact that, more often than not, the new arrivals meet no resistance in the form of natural predators or diseases which might halt their spread.

All in all, invasive species seem to be typical, if not stereotypical, villains of conservation biology. They tyrannize new habitats, throwing native populations into chaos. But is it really the full picture of the situation? Perhaps it’s time to admit that most ecosystems have been changed so dramatically by human impact that restoring them to what they once were is hardly possible, as many native species are already gone. Every system requires a balance and invasive species often fit really well in the environment, including the trophic web. Examples are many and varied, like some new plant species in California, which have become an extra source of nutrition for native butterflies. Or the new tree species in Puerto Rico, which are contributing to the regeneration of areas destroyed through deforestation. Or the zebra mussel, which made it to America from Eastern Europe and now clings en masse to underwater hydrotechnical equipment, causing clogging and failures, but – at the same time – filtering toxins out of the water.

A killer duet

Not all invasions are caused by the world’s getting smaller due to globalization or by the not-so-smart ideas of the Homo Sapiens, who continues to dabble in natural processes without fully realizing the consequences of his actions.

The expansion of invasive species is facilitated also by the ongoing climate change. One way to adapt to the changing climate is moving towards the poles. This means that that the organisms inhabiting the northern hemisphere expand their ranges northwards, where the temperatures are still relatively cool. On the other hand, climate change leads to the disappearance of physical and climatic barriers (such as sea ice and low temperatures), which enables new species to venture into regions like the Arctic, which was once well beyond their reach.

The exodus to the Arctic

But what do exotic beetles in firewood, giant toxic weed in Polish fields and recovering Puerto Rican forests have to do with the Arctic? The mechanisms of species invasion and the associated dangers are the same regardless of the area, but it is in the Arctic that climate changes occur the fastest and are felt most acutely. The local ecosystems are particularly vulnerable and trophic webs, made up of relatively few species, are hit hard by all disruptions of the natural balance.

The Arctic is still remote and hard to reach even for people equipped with modern means of transport and cutting-edge technologies to help withstand local conditions, let alone for animals or plants. There are places within the region where the access of non-native species is consciously and consistently denied. Bringing cats to Svalbard, for instance, was banned in 1992 and the last living individual passed on to the Eternal (Mice) Hunting Grounds at the beginning of 2021.

So where do the Arctic invaders come from?

For now, it is believed that fewer than 20 alien species have settled in the Arctic for good, but the increasing activity in the Arctic Ocean (marine transportation) and developing tourism may soon cause the number to rise.

Out of the 20, the best known is the red king crab, which comes from the Sea of Japan, the Bering Sea and the North Pacific. It was introduced in the Barents Sea on purpose in the 1960s and is now spreading south along the Norwegian coast and in the White Sea. Between 1961 and 1969, 1.5 million crab larvae, 10 000 juvenile crabs and over 3000 adult individuals were let into the Kola Bay to boost the annual catch and bring extra profits. The red king crab, however, led to a significant decline in the populations of crustaceans, sea urchins and other large, slow-moving bottom-dwelling species caught by local fisheries. This way another brilliant plan – this time of creating a crab fishing El Dorado – had a completely opposite effect, as the ungrateful creature continues to steal catch from fishing nets.

A major source of invasive species is ballast water discharged in the Arctic, which often contains numerous organisms from other parts of the world. Most of them are still unable to survive in the harsh environment of the Arctic Ocean but this may soon change, as the Arctic warms up as many as 6 times faster than the rest of the Earth. Even now, fishing boats around Greenland catch more and more mackerel, for which until recently the waters were simply too cold. When it comes to terrestrial invaders, the best example is one of the greatest opportunists in the animal kingdom – the red fox. The crafty little animal is not only venturing into towns, where it raids rubbish bins in search of food, but is also becoming increasing common in the Arctic tundra. It is really bad news for the Arctic fox, which is already endangered. The red fox occasionally hunts its smaller cousin, but also – and more worryingly – successfully competes with it for rodents (such as lemmings) and other food resources.

Paradise for tourists, hell for locals

Few invasive species stir up as much controversy as the Nootka lupine (Lupinus nootkatensis). As always, the beginnings were innocent enough. The Nootka lupine, native to North America, was brought to Iceland in 1945 to control soil erosion and help in its rehabilitation.

The plant’s bluish purple flowers are a magnificent sight which draws crowds of tourists and features prominently on the list of must-take tourist shots. The Nootka lupine can be found throughout the country, covering meadows and grazing lands, mountain slopes and river banks, as far as the eye can see. But the flowers soon die, tourists go home, and the locals are left surrounded with vast stretches of rotting brown. The Nootka lupine is out of control and poses a threat to native flora, especially the dwindling population of the downy birch. Some call for the plant’s eradication, however picturesque it may be, some other fear that getting rid of it might cause a drop in tourist numbers, still others consider using it as animal feed.

Strategies and successes

The significance of the problem has been noticed by the Arctic Council. In 2017, two of its work groups – Conservation of Arctic Flora and Fauna (CAFF) and Protection of the Arctic Marine Environment (PAME) – produced a strategy and action plan based on the principles of prevention, rapid detection, immediate reaction, eradication and control. Can the war against invasive species be won or is ecosystem transformation one of the processes that, once started, cannot be stopped?

The story of Hawadax provides a powerful piece of evidence that – with enough commitment and solid planning – everything is possible. The volcanic island of Hawadax belongs to the Aleutian Islands off the western coast of Alaska. From 1827 onwards, the island was known as the Rat Island, with the name inspired by the abundance of the brown rat and the damage it caused to the island’s ecosystem for over 200 years. The first rats reached the island after a Japanese ship sank in its vicinity in 1780. The rat population soon exploded, becoming a major threat to local plants and birds.

In September 2008, a government-funded rat eradication program was launched on the island and four years later the place was declared rat-free. Having bid farewell to non-native (though already well-settled) rats, the island regained its original name Hawadax (Aleut for “welcome”) and soon heartily welcomed puffins and oystercatchers, which wasted no time reclaiming the island’s rocky shores.

Author: Anna Wielgopolan

Translation: Barbara Jóźwiak