22 July 2026, by Glaubrecht/Red.

Photo: UHH/Engels

The UHH is home to more than 6,200 researchers. Every two weeks, in the “Doing the Research” series in the *Hamburger Abendblatt*, we provide insights into their work. In the current issue, Prof. Dr. Matthias Glaubrecht, professor of animal biodiversity, explains how new species affect our ecosystems.

According to the latest information from the Lower Saxony Anglers’ Association, the Volga pikeperch has been detected for the first time in the Mittelland Canal, from where it also made its way into the northern Elbe. It was likely released by anglers as a stock fish. But isn’t the release of non-native species prohibited?

In fact, there is a so-called Union List at the European level. In this list, the EU identifies non-native animal and plant species whose spread could harm native species or ecosystems and thus threaten biodiversity. It thus regulates which species may not be introduced, traded, bred, or released. Of the approximately 12,000 non-native species in Europe, however, only slightly more than 100 are on the list. The Volga pikeperch is not included on this list either, so releasing it was not prohibited.

Why the Asian hornet prompted the environmental agency to take action

There are, however, species on the list that prompt the Hamburg Environmental Agency to take action when sightings occur. Last summer, for example, this was the case with the Asian hornet. It causes economic damage because it preys on bees. The focus here is not only on our 556 wild bee species, but above all on the honeybee, because it is important for beekeeping and for plant pollination. The pesticides we apply to the landscape pose a much greater threat to honeybees, but since we cannot solve all problems at once, we are starting by controlling the Asian hornet.

Many species that are new to Hamburg have escaped from breeding facilities. The raccoon dog, native to East Asia, was bred in countries of the former Soviet Union, escaped from captivity there, and—like the raccoon, which was also bred for its fur—has spread as far as we are here. Both species feed on eggs, amphibians, insects, and small mammals, which can threaten local populations. Nutrias also play a major role here. This species, native to South America, was likewise bred on fur farms in Germany and entered the wild either through escape or deliberate release. The animals undermine dikes with their burrows, which is particularly relevant for our region.

Invasive aquatic plants spread via shipping or birds

Among plants, the glandular impatiens is spreading particularly rapidly; it actually originates from the Indian subcontinent and was introduced as an ornamental plant. It grows rapidly, depriving other plant species of sunlight and nutrients. But plants can also cause economic damage: Invasive aquatic plants such as alligator weed spread via shipping or birds and block irrigation and drainage systems as well as power plant intakes.

New species can also harm the health of humans, animals, and plants. One example is the introduced American blue crab. It transmits diseases—from which it itself is unaffected—to our European crab species. And the Asian tiger mosquito, a vector of dengue fever that has reached us via the Mediterranean region, has now found a breeding habitat here as well.

Compared to the major challenges we face in preserving biodiversity, however, invasive species are our least significant problem. Habitat loss is the number one issue. For 800 years, Hamburg has thrived on its port. That’s why we’re trying to keep it competitive by dredging the tidal Elbe. But dredging alters the habitat—to the extent that we’re losing, among other species, the smelt, a species typical of the Elbe. Its population, and that of many other species, is declining not because of a new (zander) species, but because of our massive interference with their habitats.

Thus, one immigrant species in particular plays an extreme role in species extinction—namely, humans. We immigrated to Europe from Africa, displaced the Neanderthals, and also the mammoth. So immigration has always existed; in principle, it is a natural development. But our actions are now also threatening biodiversity.

(This content has been translated automatically.)