“Warning: Do not destroy here!” “They’re all welcome,” says Nicolette Datima-Knoll (48), a snapdragon with large, raised, creeping bells. Her front yard contrasts with the neighbors’ tiled alternatives. Wild plants originate from countries with warmer climates. However, they settled in the city park of Datema-Knol in Beverwijk.
The number of new plants and animals in the Netherlands is rapidly increasing due to climate change, urbanization and extensive travel. Between 1962 and 1996 an average of two new plants per year settled permanently in the Netherlands, and now there are seven per year. The number of new animal species has averaged 27 per year since 2005, and the online monitoring platform Waarneming.nl has been registered.
Dutch cities have become a tropical paradise for outsiders – that is, for plants and animals that did not occur in Holland, but accidentally or deliberately traveled with humans. In the city, new species are given space to occupy space, by abandoned construction sites or when remodeling a park. The climate in the city is also softer due to the heat island effect: buildings, sidewalks and asphalt retain heat from the sun, heaters and air conditioners, for example.
In parks in most urban areas, one in six species spotted was an exotic. In country parks this was one in eleven. Over 17,000 observations from crowdsourcing project De Wilde Tuin participants were used in this analysis. Norwegian Refugee Council And Tilburg University, along with the participants, is investigating what naturalization does to the parks and their owners. Just like Datema-Knol, over a thousand participants passed by the plants and animals they saw in their garden between March 7 and the end of August.
Frank Heldermann, 51, from Amstelveen is also involved in the project. He is sitting in his backyard with a list in hand: the most interesting species he has seen. Helderman proudly mentions two strange species: “I saw a beautiful Mediterranean bug and a fig skeleton moth, a rare insect!” He jumps and begins to search among the fig leaves. The soft green between the veins of the leaves was eaten, but the moth could not be seen anywhere.
want is increasing. It is not the only type. Barbara Gravendeel, a professor in a special assignment to plant evolution at Radboud University, notes that there are more exotic plants and animals among the warmth-loving observations. These “lovers of warmth” are mainly seen in urban areas. “This shows that because of the warming, we are seeing more and more wild species in our gardens that are adapting to the heat.”
Because of climate change, the air in parks outside the city will also warm in the long run. Then new species can begin to spread. “Fuse, for example – plants of the nettle family – use urban gardens as a springboard in their progression from southern Europe to the north,” she says.
Gravendeel says the increasing diversity of species in the Netherlands “makes the system more flexible”. A grass with many different weeds on it and the occasional tree turns brown less quickly during drought. Most new animals can’t do any harm either. Except for a handful of invasive alien species, such as disease-carrying mosquitoes. However, some plants grow faster and more intensely due to warming, so that weeds don’t get a chance and monotony can arise.
There is no monotony in the Gardens of Datema-Knol and Helderman. Although Heldermann’s wife Karen (50 years old) is eager to pull the ashes from the ground. “These trees become very tenacious, with roots spreading underground.” The snails take them away to a nearby park. Heldermann has a different plan. Dead wood lies in the corner. “It attracts insects that eat snail eggs.”