Traditional Utilization of Weeds and Ethnic Ecological Wisdom in Longsheng Terraces—A Study Based on Globally Important Agricultural Heritage Systems

Abstract Background Weeds, which are long seen as nutrient competitors for crops, have made chemical weeding mainstream in agriculture. However, in Guangxi’s Longsheng Terraces, a global agricultural heritage site, the Zhuang, Yao and Dong peoples value them as medicine, food, feed and even tools. This undocumented traditional knowledge, under chemical agriculture and tourism pressures, is on the verge of extinction. Methods This study integrates research methods from ethnobotany and weed science and conducts a survey on 189 weed species across 11 types of farmlands, including paddy fields and corn fields in the Longsheng Terraces. It focuses on traditional knowledge of weed utilization among the Zhuang, Yao, and Dong ethnic groups. Through semistructured interviews, data on the local names, uses, utilized parts, and frequency of use of these weeds were recorded. Additionally, indicators such as frequency of citation (FC), informant consensus factor (Fic), use value (UV), and relative importance (RI) were employed to analyze their value quantitatively. Results Among the 189 weed species, 49 have traditional utilization value, covering four major categories: medicinal use (41 species, accounting for 81.6%), edible, forage, and tool material use. Among them, Phytolacca americana, Polygonum hydropiper, Plantago asiatica, and Erigeron annuus had the highest relative importance. In terms of usage consensus, there was a high level of consensus within the community regarding weed utilization knowledge for conditions such as coryza and snake bites. Notably, 29 medicinal weeds were not included in the Pharmacopoeia of the People’s Republic of China, and among the 14 weeds included therein, 9 species remain unrecorded, indicating that these weeds have potential development value. Analysis of ethnic differences revealed that the Yao ethnic group utilized the most abundant weed species, followed by the Zhuang and the Dong. The similarity coefficient analysis revealed that the Zhuang and Yao ethnic groups presented the highest similarity in weed utilization knowledge, whereas the similarity between the Zhuang and Dong ethnic groups was the lowest. The inheritance of traditional knowledge showed a significant intergenerational decreasing trend, with no gender difference observed. Additionally, the impact of tourism development on the weed utilization rate did not reach statistical significance. Conclusions This study reveals the multidimensional value of weeds in the Longsheng Terraces and the traditional ecological wisdom they embody, providing significant reference values for biodiversity conservation, traditional knowledge inheritance, and sustainable agricultural development at global agricultural cultural heritage sites. Moreover, systematic research and protective measures are needed to prevent the loss of these valuable resources due to improper management.