Ecological restoration outcomes in Rwanda’s Rugezi wetland: Biodiversity indices and food web recovery

Abstract

Wetlands play significant roles in the environment as filters of water, storehouses of carbon, flood-control zones, and habitat providers of wildlife- and they continue to be degraded. An example is Rugezi Wetland in north Rwanda: this is a Ramsar site that feeds into downstream lakes but was significantly degraded by both agriculture and drainage. This paper examines the progress of recent restoration there with an eye towards biodiversity and the structuring of the food web. A mixed-methods research approach was employed by the research team: systematic field surveys in and after the restoration, metrics of water quality (water nutrient concentrations, dissolved oxygen, turbidity) and maps of the habitats using GIS analysis were developed. They also tallied important figures of biodiversity (species richness, Shannon-Wiener index) and monitored the presence of the species in case of plants, birds, fish, amphibians, and invertebrates. Results show marked improvements post-restoration. The Shannon-Wiener index for wetland vegetation rose from ~1.0 to >2.0, and overall plant species richness increased (e.g. the return of diverse aquatic plants such as Lemna spp. and Vossia spp.). Bird species count climbed from 35 (in 2007) to 85 (in 2023), including recoveries of specialists like the Grey Crowned Crane (Balearica regulorum) and Shoebill (Balaeniceps rex). Fish populations (notably Oreochromis and Barbus spp.) rose from ~15,000 (in 2017) to 22,000 (in 2024), and invertebrate species richness expanded by 72 species. Hydrological and habitat restoration increased the open water area by ~12% and improved water quality: dissolved oxygen rose from ~4.2 to 7.8 mg/L, while nitrogen and phosphorus concentrations fell by ~56% and ~63%, respectively, reducing eutrophication risk. Illegal extraction of wetland resources declined, and over 3,500 community members adopted sustainable activities (beekeeping, ecotourism). The restoration of Rugezi Wetland has markedly enhanced biodiversity and strengthened food web interactions. Increases in diversity indices and higher trophic populations demonstrate recovery of ecological functions. Sustained conservation measures, including protection of habitat, invasive species control, and community engagement, will be essential to maintain these gains.