For years, cities have treated non-native plants like the enemy—the invaders destroying local ecosystems. But researchers in Berlin just upended that assumption with data that challenges where conservation efforts should actually focus.
A study of 1,231 populations of 201 endangered plant species across Berlin found that non-native plants threaten only 15.2% of them. Native species—the ones already there—pose nearly the same risk at 16.0%. The real culprits are something else entirely: aggressive plant competition, agricultural runoff, nutrient pollution, and the constant pressure of urban development.
"Non-native species are often blamed for biodiversity loss in cities, but our results tell a different story," says Ingo Kowarik, the study's lead researcher at the Technical University of Berlin. "In Berlin, other pressures—including highly competitive native species—pose a much greater threat."
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Start Your News DetoxThis matters because cities have limited conservation budgets. If you're spending resources removing non-native plants when the real problem is nutrient pollution or invasive native species choking out the endangered ones, you're fighting the wrong battle.
The research, published in the Journal of Applied Ecology, analyzed threats at multiple scales—looking at individual plant populations, entire species, and different habitat types across the city. What emerged was a more complicated picture than "native good, non-native bad." Biological threats dominated, but they came from multiple directions. Some came from outside; many came from within.
The implication is straightforward: effective urban conservation requires precision. It means identifying which specific pressures are actually driving decline in each habitat, then targeting those. Sometimes that's removing a non-native species. Often it's managing soil nutrients, controlling aggressive native plants, or buffering endangered species from development pressure.
Berlin's Flora Protection Program has been tracking these populations for years, giving researchers an unusually detailed dataset. That granularity is what made this finding possible—and it's a model other cities are watching. As urban areas expand and plant populations fragment, understanding what actually threatens them becomes the difference between conservation that works and conservation that just feels good.
