T = 2 (300–2000 mg/kg; reversible irritation, symptoms <6–12h) B. thunbergii contains isoquinoline alkaloids: berberine, berbamine, oxyacanthine. Berberine LD₅₀ (rat, oral): ~329 mg/kg. Red berries mildly toxic: GI irritation (nausea, vomiting, diarrhoea) upon ingestion of significant quantities; sour taste limits voluntary overconsumption. Symptoms reversible and self-limiting within 6–12h. No documented human fatalities in Europe (last 10 years). Hospitalisations >48h not documented for acute berry ingestion. T=3 not assigned: obligate prolonged medical intervention not documented as typical outcome. Sources: Frohne & Pfänder (2005); Bruneton (2009) Pharmacognosie; CAPB plant database (Berberis entries).
A = 2 (moderate symptoms, temporary disorders) Berberine and related alkaloids cause moderate GI disturbance and transient cardiovascular effects in animals upon significant ingestion. ASPCA does not specifically list B. thunbergii as severely toxic; general Berberis toxicity profile indicates moderate reversible effects. Serious illness or prolonged recovery not consistently documented at field exposure → A=3 not assigned. Sources: ASPCA APCC; Cooper & Johnson (1998); Frohne & Pfänder (2005).
I=3 — B. thunbergii forms dense self-sustaining understory thickets in temperate deciduous forests, documented across Belgium, Germany, France, and extensively in North America. Ecological impacts include reduction of native herbaceous diversity, alteration of soil chemistry and microclimate, and increased tick habitat density. Persistent recruitment outside cultivation confirmed in comparable forest ecosystems. Cross-border data applicable under TAI-ECOSAFE methodology for species with established naturalisation in ecologically equivalent habitats.