Raccoons and invisible fungi sink their teeth into Estonian habitat

A raccoon.
A raccoon. Source: Quentin Bounias/Unsplash

Due to climate change and human activity, several invasive plant and animal species have already arrived in Estonia, threatening the native flora and fauna. While raccoons and red-eared sliders may become established in Estonia over the next decade, the greatest strain is on the Baltic Sea.

In the past year alone, there have been sightings of a raccoon wandering around Tartu County, a sea urchin at Pirita beach, a bat ray in Pärnu, a walrus roaming in Finland and even a whale sighting.

"During the past two decades, the issue has clearly grown." Eike Tammekand, chief of the Environmental Board's nature conservation department, told on ERR's TV program "Pealtnagijja" ("Eyewitness") that alien species are the second leading cause of biodiversity loss globally."

Globalization and the opening of borders play a key role here. This is especially true with marine species. "When deciding whether to eat Chinese or other imported foods, we should consider the potential consequences," professor of marine ecology at the University of Tartu Jonne Kotta said.

According to scientists, it is essential to differentiate between species that were intentionally or unintentionally introduced by humans and animals whose range has been affected by human activity, such as climate change.

For instance, the jackal, which was first spotted in Estonia in 1983, has now established itself here.

It is not strictly speaking an alien species, but rather a novel species.

"As the temperature is warming, northern habitats are becoming more suited for the species. They are headed northward. Human landscaping also contributes in some ways to this, with some landscape elements shifting and making it more favorable for animals to migrate," Tiit Maran, zoologist and director of the Tallinn Zoo, explained.

A raccoon was spotted in a forest in Kambja, Tartu County, in January, and it even made the "AK" news. It was eventually revealed that it was a pet named Mõmmik. However, Maran said that it is just a matter of time before the North American hero becomes also a permanent Estonian resident.

"Why shouldn't it come here if the temperature is warming and living conditions are improving in the southern end of the Baltics? We cannot construct a Chinese wall around Estonia to keep out species that would naturally migrate north," Maran added.

Invasive intruders

According to biologists, there is no purpose in slowing down natural migration, but it is a different story for alien species introduced by humans. After a few years in the wild, they may no longer appear strange to the untrained eye.

This is true, for example, of the himalayan balsam (impatiens glandulifera). "It is a delightful decoration that comes from the Himalayas and is now widespread throughout Europe. However, it grows so quickly and in such dense masses that nothing else can grow with it. My colleague discovered the first Himalayan balsam plant in a protected park area about fifteen or twenty years ago. He said it was a terrifying thing," Eike Tammekänd recollected.

The Estonian Environment Agency is primarily responsible for the regulation of foreign species, and their website contains several dozen plants and animals that are prohibited from being introduced or bred in Estonia.

The longest-standing problem in Estonia, which they have been fighting for 17 years, is the giant hogweed and sosnovsky's hogweed. They were originally planted here as silage plants, but they grew out of control.

Over the years, the eradication campaign has spent approximately €7.5 million, including €405,000 only this year. Additionally, efforts are being made on a smaller scale to eradicate the broad-leaved ragwort, (senecio sarracenicus) and reynoutria (reynoutria japonica houtt).

The Spanish snail is an example of a foreign species that has inadvertently arrived in Estonia. "In any case, the outburst and the larger concern occurred only a couple of summers ago. It is yet another example of a foreign species that has quietly invaded. It crept in gradually, and then there were warm winters, wet springs and summers, and then it suddenly multiplied tremendously."

Because a single snail can produce up to 400 offsprings, the population can explode in as little as 10 individuals. As a result of this act, some people have already given up gardening, Tammekänd said.

The Environmental Board has a map app for both insects and hungry beetles that anyone can use to report their findings, as monitoring and controlling invasive species is really important.

One such example is the tiny, almost invisible fungus commonly known as ash-tree-menace, which was probably brought here from Asia on tree stumps.

Ash trees are weakened and eventually killed by the this fungus. "We have hundreds of species associated with ash trees, many of which are rare; perhaps we should consider the economic damage they cause as well as the impact on wildlife. And it is only this one tiny fungus to blame," Tammekänd continued.

Dread of the sea

In previous periods, species spread alongside humans, but they were not able to traverse such vast distances so quickly. Even apparently similar species can experience and adapt to the same environment differently.

For instance, Baltic mussels can be compared to rangia cuneata, or Atlantic rangia, also known as wedge clam, a Mexican newcomer. "A professional will be able to distinguish between the two, but if the rangia clam can flourish here, it will grow approximately ten times larger. There is already quite a bit of this meaty body, which is suitable for cooking," Kotta said.

A distant visitor most likely arrived in Estonia with ship ballast water. Experts believe that the most serious problems with alien species exist in Estonia's seas and other bodies of water. An alien species does not have to be large and dangerous to have a significant impact, such as the polychaete. "It's similar to an earthworm, but leggier. We thought it was a big deal because it was displacing some of our native species and wreaking havoc on other minor ecosystems, said Kotta. However, new and far more sinister species appeared over time.

However, alien species are far more difficult to control than native species.

"Aquatic ecosystems and bodies of water are perhaps a bit of a mystery to us because we don't inhabit them. We do not know exactly what is there and in which quantity. This is one of the reasons why there are no particularly effective methods for eliminating these alien species," explained Tammekand.

Kotta said the worst alien species for the Baltic Sea are those that would take up a role that previously did not exist here. As a young sea, there are numerous ecological niches that have yet to be occupied, the marine ecologist said. "If we obtain a species that fulfills this function, the entire ecosystem could be turned on its head."

The round goby (neogobius melanostomus) and the estuarine mud crab (rhithropanopeus harrisii) are the most well-known examples. The first may be easily cooked, while the second requires little effort. More than one hundred of them may inhabit a single square meter. Despite being smaller than a euro coin, each one can peel a hundred clams per day. Kotta explains, "It's like a swarm of migratory grasshoppers that dart across the seafloor and, like a vacuum cleaner, vacuum up everything that was there before." On the long term, they could alter the entire aquatic food web. In turn, this degrades water quality. The Baltic Sea's turbidity is increasing, Kotta said.

A critical but non-fatal development

This summer, a walrus (odobenus rosmarus) was first discovered on a Latvian coast and later spotted in Finland, causing great excitement. According to biologists, the walrus traveled south from its native environment and attempted to return north, but took a wrong turn in the Danish Straits and became trapped in the Baltic Sea. This summer, someone reportedly stumbled on a sea urchin (echinoidea) on Pirita Beach, and a bat ray-like fish was photographed in shallow waters of Pärnu Bay. And large creature, thought to be a whale, was spotted in the water off the coast.

While whales do stray into the Baltic on occasion, experts are skeptical of sea urchins or a bat ray fish. At most, it was a pet dumped into the sea from an aquarium, and it was certainly a death sentence. "Even with these alien species, we don't have anything dangerous or poisonous here. Although, anything that arrives or appears here could cause an indirect impact on fisheries, water quality, and so on. At this time there is very little concern about anyone dying or being directly affected," Kotta said.

In mid-September, a high-level symposium in Tartu, Estonia, demonstrated that invasive species — their invasion and impact — are one of today's most pressing conservation issues. It was organized by Estonian specialists and brought together 260 specialists from around the world.

On the one hand, scientists recognize that many processes are too complicated for humans to manage and that not everything can be regulated, but we must nonetheless be aware of what is happening.

"The most important task is to put in place a response mechanism as early as possible. As time passes, some alien species will get more spread out day by day, week by week, month by month and year by year," Maran said.

Despite the possibility of evolutionary success, nature is becoming increasingly monotonous and the ecosystem is no longer able to fulfill all of its functions.

"With certain species, we will have to give up: they are already so pervasive and potent, yet it is important to try to retain their uniqueness and, ideally, a healthier and safer environment for all other species as well," said Tammekand.


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Editor: Kristina Kersa

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