Rising temperatures are expected to increase pest populations across the Netherlands, with urban areas seeing a higher likelihood of rat encounters and oak processionary caterpillars.
Data compiled by weather service Weeronline shows that reports of rats in major Dutch cities have steadily climbed over the last 12 years.
Milder winters encourage urban breeding
Warmer winter conditions allow a larger number of rodents to survive through the cold months.
Because fewer animals die in the winter, the surviving population can begin breeding earlier in the spring season.
Urban center temperatures tend to remain slightly higher than rural areas, which further aids their survival.
However, experts note that municipal food waste management and public cleanliness remain major factors in controlling the local rat population.
Caterpillar numbers linked to tree planting
Oak processionary caterpillars have been documented in the country for over 30 years, but their presence expanded rapidly in recent seasons.
The caterpillars thrive partly because widespread oak tree planting provided an extensive food supply, though targeted control efforts by regional authorities have improved in recent years.
The nuisance caused by the caterpillars typically peaks between mid-May and mid-July, when their microscopic stinging hairs can trigger severe skin irritation and respiratory problems.
Broader shifts in local ecosystems
While specific pest populations are expanding, insect numbers overall are declining both globally and within the Netherlands.
Changes in agricultural practices, land usage, and expanding city infrastructure continue to impact insect biodiversity.
Because insects form a key part of the food chain, the decline of certain natural predators can inadvertently trigger outbreaks of other resilient pest species.
