Impact of urbanization on soapnut Sapindus trifoliatus L. tree cover and the need for community involvement: a case study from Kochi, Kerala, India

• Published in: Biodiversity (Nepean) 2024-10, Vol.25 (4), p.357-369
• Main Authors: Waran, Archana, Manchi, Shirish, Pathak, Prasad, Chandran, Preethy
• Format: Article
• Language: English
• Subjects: Agricultural land; biodiesel; Biodiesel fuels; biodiversity; Biofuels; Biopesticides; case studies; citizen science; Community involvement; community service; Detergents; Evergreen trees; extinction; fruits; habitat destruction; Habitat loss; India; Kochi; mapping; Pesticides; Sapindus trifoliatus; soapnut; Species extinction; Trees; Urbanization
• ISSN: 1488-8386; 2160-0651; 2160-0651
• DOI: 10.1080/14888386.2024.2416662

The South Indian soapnut tree, Sapindus trifoliatus L, is a midsized evergreen tree from the Indian subcontinent whose fruit can produce natural detergents, biodiesel, and biopesticides. In this study, we document the systematic destruction of soapnut trees through a citizen-supported tree census in an emerging Tier 2 city, Kochi, in South India. In the study, 3580 respondents allowed us to find and map 210 locations of soapnut trees across 411.57 km 2 . Kochi expanded suddenly in the early 2000s, with a drastic increase in built-up area (126%) and a steady decline in wetlands (57.6%) and croplands (15%). Habitat loss and removal from home gardens has quartered soapnut tree density, to 0.11 km −2 . With only 50 trees remaining, the population of the South Indian soapnut will reach the brink of local extinction by 2080. Citizens have the power to conserve soapnut trees outside protected areas, yet only 3.41% of respondents were well informed. Knowledge transfer regarding biodiversity is being lost across generations. Frequently updating People's Biodiversity Registers is essential to document and conserve biodiversity within cityscapes. Citizen reporting provides deeper information and data points than the work of expert taxonomists alone, provided the species is familiar to the locals. Regular population census with GIS mapping and citizens' input can effectively monitor populations within urban refugia. The collection of soapnuts and the protection of trees on private property should be incentivized through policy change and accessibility and benefit sharing agreements.