Three kinds of ants, fire ants, crazy ants, and pharaoh ants, along with a goldfish, an ocean tree, a red palm weevil, and members of the mongoose and heath family (excluding the European mongoose) are among the species discussed here. They are part of the Spanish Catalog of Invasive Alien Species, which prohibits possession, transport, and trade of these organisms.
These species are labeled invasive due to their distinct impacts on ecosystems. In some cases, as with ants, entries in the Catalogue appear before or soon after discovery, often because of prevention efforts coordinated by Life, the program responsible for safeguarding biodiversity. The Invasaqua project of the Iberian Ichthyology Society, represented by Frederic Casals, contributed a notable photograph during this discussion.
Fire ants, crazy ants, and Pharaoh ants often arrive as stowaways through the wood trade or gardening shipments, according to Casals, who teaches in the Department of Animal Sciences at the University of Lleida. He notes that their appearance on official lists is an important signal for preventive measures.
1. Red palm aphid
A giant aphid-like insect, part of a lice family, measures seven to eight centimeters long and has persisted in Spain for decades, causing extensive damage to palm trees across multiple regions.
2. Mioporo
This tree variety, widely used in horticulture in the southern hemisphere, has become a cautionary example for public works. Casals emphasizes the need for careful control of species used in public projects to prevent unintended ecological consequences due to insufficient coordination.
3. Mongooses and meerkats
Another challenge in the trade linked to pet ownership is the proliferation of animal samples. Some animal welfare groups view this as unnecessary pet ownership, noting the presence of raccoons in Madrid as a related concern. Mongooses and meerkats can be kept as pets, but when adults are stressed or released, they often disrupt local biodiversity in unforeseen ways.
Mongooses and meerkats can thrive in urban settings if released after being kept as pets, yet their introduction can threaten native species when released into the wild. Such releases may lead to competition, predation, and disease transmission that native wildlife are ill equipped to handle.
The raccoon is frequently cited as a close example: it is highly adaptable, omnivorous, and can be aggressive toward humans. In similar fashion, mongooses and meerkats are expected to exert significant direct impacts on native fauna when escape and establishment occur.
4. Ants
Several ant species are considered potentially invasive because it remains unclear whether they will form stable populations or cause notable harm. For instance, while the sting and venom of the fire ant are well-known, the direct threat to human health in any given area can be unpredictable. Exotic ants that have persisted for years or decades may gradually alter habitat, climate interactions, and land-use patterns, contributing to broader ecological shifts.
Ant invasions often mirror broader environmental changes, including shifts in weather patterns and land management practices, which can amplify their spread and ecological impact.
5. Aquarium fish
This group, commonly found in home aquariums, has shown up in natural water bodies such as the Vallvidrera reservoir near Barcelona, part of the Sierra de Collserola Natural Park. Draining measures are sometimes necessary to protect both the reservoir ecosystem and other native species affected by introduced fish and other invaders like carp.
In the same reservoir area, occasional released fish, turtles, or other pets have created local ecological disturbances—a pattern seen in many aquatic systems when owners abandon animals. The large-scale Chinese mystus-like fish Paramisgurnus dabryanus, though not inherently more dangerous than other invasive species, is listed due to its ecological footprint and the site where it was promoted into the official catalog.
The reservoir area is considered vital for protecting native amphibian populations, and Nature Park managers periodically drain the water to remove invasive species that prey on eggs, tadpoles, and adult amphibians.
The primary concern highlighted by this expert is the ease of acquisition enabled by online marketplaces. The ability to purchase various fish species online, even when such purchases may be legally restricted, underscores the need for proper oversight and stronger controls in commerce.
Even though some species have been eliminated, Casals explains what occurred in tropical regions where sudden changes in water level forced species to burrow and hibernate in the mud, allowing them to persist under the surface until conditions improved.
These findings underscore the ongoing tension between human activity, trade, and ecological integrity. The catalog and related enforcement efforts serve as a guide for conservationists, policymakers, and the public to reduce the risk of invasive species establishing themselves and disrupting native ecosystems.