Road Encroachment Near Protected Areas Alters the Natural Soundscape Through Traffic Noise Pollution in Costa Rica

Abstract

Road networks are spatially disposed across landscapes and are differentially used by traffic, generating levels of noise that may negatively affect protected areas. The objective of this study is to quantify the length of road stretches in contact and in close proximity to protected areas, and to investigate differential effects parks may have in relation to traffic volumes and noise pollution. We measured road networks in proximity to protected areas using a geographic information system and the Atlas of Costa Rica. Noise and traffic volumes were quantified in three protected areas with direct adjacency with roads. We generated environmental sound maps to assess the influence of noise on natural sounds, such as those produced by streams (geophony) and birds (biophony). We recorded biophony close and far to the road in one of the protected areas. We found that 70 protected areas are directly or indirectly affected by road proximity. Noise was greater in roads with higher traffic usage than those with lower traffic usage, but the type of vehicles also influenced noise levels. Noise penetrated the forest with greater levels during the dry season than in the wet season. We found that the amount of biophony in seconds was lower close than far from the road, and that the stream sound was masked by traffic noise. Our results suggest that noise may contribute to habitat degradation through a decrease and loss of natural sounds, decreasing the quality of biodiversity protection. Interdisciplinary action and rigorous planning must be considered to avoid road encroachment on protected areas.

Keywords

• Anthrophony
• biodiversity conservation
• biophony
• geophony
• soundscape conservation
• traffic volume