Cumulative Impacts of Land Cover Change and Dams on the Land–Water Interface of the Tocantins River

Abstract

Riparian vegetation performs important ecosystems services, improving water quality, mitigating erosion, and maintaining regional plant and animal biodiversity. Regular annual flooding maintains riparian forests through an intermediate disturbance regime. In response, seasonally flooded vegetation has developed adaptations for seed dispersal and gas transfer to survive and reproduce while undergoing periods of flooding. In the Amazon, a dam building boom threatens the integrity of riparian vegetation by moving riparian corridors into dry-adapted ecosystems and reducing downstream flooding of riparian areas. Additionally, the region is undergoing intense development pressure resulting in the conversion of native riparian vegetation into agriculture. In this study, we measure how the installation of six large dams on the Tocantins River, coupled with land cover change from native forest and savanna to cattle pasture, has changed the land–water interface of this region. Using land cover data provided by MapBiomas, we quantified land cover change from 1985 to 2018 and measured changes in the riparian areas of the still free-flowing areas of the Tocantins River, riparian areas surrounding reservoirs, and in-stream vegetation dynamics. We found that deforestation in the riparian areas of the Tocantins River downstream of the dams is occurring at a higher rate than deforestation in the watershed. Additionally, reservoir filling resulted in creating hundreds of square kilometers of new riparian areas, pushing the riparian zone away from forest-dominated ecosystems into savanna-dominated areas. The quantity of in-stream vegetation throughout the study was dynamic and initially increased after damming before declining for the last decade of the study. Changes to native land cover in riparian areas of the Tocantins River threaten the integrity of ecosystem services provided by riparian vegetation and are likely to lead to further degradation of these areas.

Before and After: A Multiscale Remote Sensing Assessment of the Sinop Dam, Mato Grosso, Brazil

“…While other studies have used pre-existing land cover datasets (e.g., [96]), to infer the impact of hydroelectric reservoirs on the landscape, there is substantial variability in the amount of forest and non-forest classes in both national and global datasets [5]. Hence, relying on such global datasets to assess the impact of hydroelectric reservoirs may not be adequate.…”

The land–river interface: a conceptual framework of environmental process interactions to support sustainable development

“…'land-water interface', 'land-freshwater interface', 'river-land interface', and 'river-riparian interface'), they neither encompass the same range of processes that we propose nor explicitly consider two-way interactions between aquatic and terrestrial environments. Some previous terms have been used within a single discipline to describe ecological habitat gradients (ecotones) or mosaics (Jaiswal and Pandey 2019;Swanson and Bohlman 2021), the influence of riparian vegetation and channel morphology on river water quality and aquatic ecology (Karr and Schlosser 1978), and the input of resources from rivers to the land surface (Richardson et al 2010;Tonkin et al 2016;Terui et al 2017). By formally defining the LRI and delineating it based on river processes that influence the landscape, our intention is to facilitate the interdisciplinary identification and explanation of the causal linkages between development activity and its environmental impacts.…”

Bayesian belief networks for the analysis of the controversial role of hydropower development in the antagonistic agrofood-fisheries nexus: A potential approach supporting sustainable development in the Guayas river basin (Ecuador)

“…Researchers have shown that Latin America has only 25% potential to build hydropower dams in terms of suitable sites (Gernaat et al, 2017). However, the hydropower production installations are affecting aquatic biodiversity and agricultural production in river basins worldwide (Yoshida et al, 2020;Swanson & Bohlman, 2021). Apart from the antagonistic agrofood-fisheries nexus previously discussed, also energy plays a role in the sustainable development of the GRB.…”

“…Hydropower is the most important renewable energy source to date and dams are being developed in an upward trend (Gernaat et al, 2017). However, research has shown that hydropower dams and reservoirs can negatively affect ecosystems (Ren et al, 2019;Swanson & Bohlman, 2021). There is a need for models incorporating the nexus elements to approach the interactions and challenges in an integrated way (Leng et al, 2017).…”