Impacts of sediment derived from erosion of partially-constructed road on aquatic organisms in a tropical river: The Río San Juan, Nicaragua and Costa Rica

Abstract

Throughout the humid tropics, increased land disturbance and concomitant road construction increases erosion and sediment delivery to rivers. Building road networks in developing countries is commonly a priority for international development funding based on anticipated socio-economic benefits. Yet the resulting erosion from roads, which recent studies have shown result in at least ten-fold increases in erosion rates, is not fully accounted for. While effects of road-derived sediment on aquatic ecosystems have been documented in temperate climates, little has been published on the effects of road-induced sediment on aquatic ecosystems in developing countries of the tropics. We studied periphyton biomass and macroinvertebrate communities on the deltas of Río San Juan tributaries, comparing north-bank tributaries draining undisturbed rain forest with south-bank tributaries receiving runoff from a partially-built road experiencing rapid erosion. Periphyton biomass, richness and abundance of macroinvertebrates overall, and richness and abundance of Ephemeroptera, Plecoptera and Trichoptera were higher on the north-bank tributary deltas than the south-bank tributary deltas. These findings were consistent with prior studies in temperate climates showing detrimental effects of road-derived fine sediment on aquatic organisms. A Non-Metric Multidimensional Scaling (NMDS) analysis showed the impacted community on the south-bank deltas was influenced by poorly-sorted substrate with greater proportions of fine sediment and higher water temperatures.

Soil erosion associated with roads—A global review and statistical analysis

“…Consequently, this poses a significant threat to the habitat and aquatic life within the watershed. Although researchers have explored the impact of sediment on phytoplankton biomass and large invertebrate communities (Akbarimehr et al, 2016; Touma et al, 2020), further research in this area is warranted. The disruption of the soil‐water nutrient balance within the watershed due to road influences represents a critical concern in terms of its detrimental effects on the ecological environment.…”

Response of Sediment Connectivity to Altered Convergence Processes Induced by Forest Roads in Mountainous Watershed

“…In addition to the transport pathways and confluence process of the catchment, the terrain and spatial proximity characteristics of roads and streams were also significantly correlated with IC. Relevant studies have shown that TR should be an important factor affecting the transport efficiency of sediment-loaded runoff [7,61] by altering the velocity and erosion-deposition processes [41], and thus influencing the transport processes [52,59]. This is likely related to the fact that the transmission efficiency (distance) will be higher (farther) as slope and flow velocity increase, while the transmission efficiency (distance) will be lower (shorter) as relief degree and deposition rate increase [21,34,61].…”

“…With the intensification of human activities such as forest logging, tourism development, and mineral mining, road-related soil erosion has increasingly attracted the attention of academic researchers and government management departments [3,4]. Although the area percentage of roads in a watershed is relatively low, they change the topographical and hydrological processes within watersheds by creating and exacerbating soil erosion [5] and affect the generation and transmission of runoff and sediment [6,7], thus significantly influencing the structure, process, and function of the watershed [1]. In mountainous watersheds that are sensitive to human activities and prone to erosion, the continuous expansion of roads through the restoration of old and abandoned roads for logging, the renovation of existing roads, and the construction of new planned roads [4] has led to fragmented forest landscapes in the watershed, disturbed water and sediment transport processes, and aggravated soil erosion, and thus seriously threatens the stability of the mountainous ecosystem [5].…”

“…Roads not only contribute to the production of sediment, but they also have a profound impact on the confluence process of surface runoff [8][9][10]. On the one hand, road-induced soil erosion is an important sediment source in watersheds [7]. Studies have shown that pavements combined with vegetation removal are bound to reduce infiltration rates and increase the rainfall-runoff coefficient compared to natural hillslopes, thus improving the potential of road erosion, and resulting in considerably higher runoff and sediment loads [11].…”

Conservation of Latin America freshwater biodiversity: beyond political borders

“…Failure to manage 109 transboundary basins and their ecosystems collectively, can result in conflicts among 110 nations (e.g. Rios-Touma et al, 2020). 111 112 Develop and harmonize transnational data collection and monitoring.…”