'From the sky to the ground': fishers' knowledge, landscape analysis and hydrological data indicate long-term environmental changes in Amazonian clear water rivers

Carolina B Nunes; Kaluan C Vieira; Paula E R Pereyra; Gustavo Hallwass; Cristiane V Cunha; Renato A M Silvano

doi:10.1016/j.scitotenv.2023.166763

'From the sky to the ground': fishers' knowledge, landscape analysis and hydrological data indicate long-term environmental changes in Amazonian clear water rivers

Sci Total Environ. 2023 Dec 15:904:166763. doi: 10.1016/j.scitotenv.2023.166763. Epub 2023 Sep 4.

Authors

Carolina B Nunes¹, Kaluan C Vieira², Paula E R Pereyra², Gustavo Hallwass³, Cristiane V Cunha⁴, Renato A M Silvano⁵

Affiliations

¹ Programa de Pós-graduação em Ecologia e Departamento de Ecologia, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil. Electronic address: carolbatistanunes@gmail.com.
² Programa de Pós-graduação em Ecologia e Departamento de Ecologia, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
³ Fisheries and Food Institute (FIFO), Rio de Janeiro, Brazil; Instituto de Ciência, Tecnologia e Inovação, Programa de Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras (UFLA), Lavras, MG, Brazil; Programa de Pós-Graduação em Ecologia Aquática e Pesca, Universidade Federal do Pará (UFPA), Belém, PA, Brazil.
⁴ Faculdade de Educação do Campo, Universidade Federal do Sul e Sudeste do Pará (UNIFESSPA), Marabá, PA, Brazil.
⁵ Programa de Pós-graduação em Ecologia e Departamento de Ecologia, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Fisheries and Food Institute (FIFO), Rio de Janeiro, Brazil.

PMID: 37666343
DOI: 10.1016/j.scitotenv.2023.166763

Abstract

Fishers possess detailed local ecological knowledge (LEK) which can be a valuable resource for tracking long-term environmental changes in less studied tropical rivers. Our goal was to investigate such changes in three clear water rivers in the Brazilian Amazon, focusing on hydrology, water quality and land cover. Additionally, we aimed to compare these changes among three rivers (Trombetas, Tapajós and Tocantins) representing a potential gradient of environmental changes. We interviewed 129 fishers (67 in Tapajós, 33 in Tocantins and 29 in Trombetas), and analyzed temporal series on land cover and hydrology respectively through maps produced by the project MapBiomas, and data from the Brazilian National Water Agency across the last 34 years (from 1985 to 2019). The complementary analyses of these three databases (mapping, hydrological data and fishers' knowledge) revealed environmental changes in the studied rivers. The maps showed a gradient of anthropic changes on land cover, from the less altered Trombetas river, the moderately altered Tapajós and the more intensely changed landscape in the Tocantins River. Fishers from the Tocantins River reported a greater variety of negative changes in water quality related to anthropic actions, such as dams, deforestation, and pollution. Additionally, most fishers indicated hydrological changes making the Tocantins River drier in more recent years, which would cause negative effects on fish populations. In the Tapajós River, fishers mentioned more varied hydrological patterns and negative effects on water quality linked to mining activities, whereas in Trombetas fishers perceived increased floods. The changes mentioned by the interviewed fishers matched observed trends from hydrological data indicating a trend of increasing droughts in the more impacted Tocantins River. Fishers' knowledge provided exclusive 'on the ground' data to track long-term changes on local hydrology and water quality, as well as inform the effects of these changes on fish and fisheries.

Keywords: Climatic changes; Dams; Environmental impacts; Landcover changes; Local ecological knowledge; Small-scale fisheries.