Long-term noise pollution affects seedling recruitment and community composition, with negative effects persisting after removal

Species diversity and interspecific information flow

Interspecific information flow is known to affect individual fitness, population dynamics and community assembly, but there has been less study of how species diversity affects information flow and thereby ecosystem functioning and services. We address this question by first examining differences among species in the sensitivity, accuracy, transmissibility, detectability and value of the cues and signals they produce, and in how they receive, store and use information derived from heterospecifics. We then review how interspecific information flow occurs in communities, involving a diversity of species and sensory modes, and how this flow can affect ecosystem-level functions, such as decomposition, seed dispersal or algae removal on coral reefs. We highlight evidence that some keystone species are particularly critical as a source of information used by eavesdroppers, and so have a disproportionate effect on information flow. Such keystone species include community informants producing signals, particularly about predation risk, that influence other species' landscapes of fear, and aggregation initiators creating cues or signals about resources. We suggest that the presence of keystone species means that there will likely be a positive relationship in many communities between species diversity and information through a 'sampling effect', in which larger pools of species are more likely to include the keystone species by chance. We then consider whether the number and relative abundance of species, irrespective of the presence of keystone species, matter to interspecific information flow; on this issue, the theory is less developed, and the evidence scant and indirect. Higher diversity could increase the quantity or quality of information that is used by eavesdroppers because redundancy increases the reliability of information or because the species provide complementary information. Alternatively, there could be a lack of a relationship between species diversity and information if there is widespread information parasitism where users are not sources, or if information sourced from heterospecifics is of lower value than that gained personally or sourced from conspecifics. Recent research suggests that species diversity does have information-modulated community and ecosystem consequences, especially in birds, such as the diversity of species at feeders increasing resource exploitation, or the number of imitated species increasing responses to vocal mimics. A first step for future research includes comprehensive observations of information flow among different taxa and habitats. Then studies should investigate whether species diversity influences the cumulative quality or quantity of information at the community level, and consequently ecosystem-level processes. An applied objective is to conserve species in part for their value as sources of information for other species, including for humans.

Pre- and postnatal noise directly impairs avian development, with fitness consequences

Noise pollution is expanding at an unprecedented rate and is increasingly associated with impaired reproduction and development across taxa. However, whether noise sound waves are intrinsically harmful for developing young-or merely disturb parents-and the fitness consequences of early exposure remain unknown. Here, by only manipulating the offspring, we show that sole exposure to noise in early life in zebra finches has fitness consequences and causes embryonic death during exposure. Exposure to pre- and postnatal traffic noise cumulatively impaired nestling growth and physiology and aggravated telomere shortening across life stages until adulthood. Consistent with a long-term somatic impact, early life noise exposure, especially prenatally, decreased individual offspring production throughout adulthood. Our findings suggest that the effects of noise pollution are more pervasive than previously realized.

A study of the relationship between rear-of-wheel particle emissions and close-proximity tire/road noise of a passenger car

Non-exhaust particulate emissions and road traffic noise will continue to constitute significant threats to the environment and human health during the 21st century. In the EU alone, >60 million adults are subjected to unhealthy levels of vehicle noise, while over 200,000 premature deaths are caused by chronic exposure to excessive concentrations of fine particles, with road traffic being a key source. Although these pollutants share common sources and can affect the same targets, studies have often treated their emissions separately. This study establishes both the phenomenological and mathematical relationships between tire/road noise (TRN) and rear-of-wheel particle (RoWP) emissions. Information from test track measurements, coupled with correlation-based models, enables linking TRN with RoWP emissions through variables such as vehicle speed and pavement properties, including macro-texture scales. A careful examination of the data reveals that pavement macro-texture acts as a crucible in which TRN and RoWP emissions are generated in an interrelated manner. However, at speeds over 70-80 km/h, the depletion of readily mobilizable RoWP fractions, followed by the emergence of refractory (hard-to-mobilize) circum-/super-micron RoWP fractions from resuspension (which accompanies the intensification of air-pumping TRN generation mechanisms), marks a loss of this interdependence. These results, supplemented by valuable insights into the particulate emission performance of pavements, serve to outline future air quality challenges and provide a basis for the simplified monitoring and control (e.g. through acoustic measurements) of RoWP emissions.

Inequalities in noise will affect urban wildlife

Understanding how systemic biases influence local ecological communities is essential for developing just and equitable environmental practices that prioritize both human and wildlife well-being. With over 270 million residents inhabiting urban areas in the United States, the socioecological consequences of racially targeted zoning, such as redlining, need to be considered in urban planning. There is a growing body of literature documenting the relationships between redlining and the inequitable distribution of environmental harms and goods, green space cover and pollutant exposure. However, it remains unknown whether historical redlining affects the distribution of urban noise or whether inequitable noise drives an ecological change in urban environments. Here we conducted a spatial analysis of how urban noise corresponds to the distribution of redlining categories and a systematic literature review to summarize the effects of noise on wildlife in urban landscapes. We found strong evidence to indicate that noise is inequitably distributed in redlined urban communities across the United States, and that inequitable noise may drive complex biological responses across diverse urban wildlife, reinforcing the interrelatedness of socioecological outcomes. These findings lay a foundation for future research that advances relationships between acoustic and urban ecology through centring equity and challenging systems of oppression in wildlife studies.

Noise pollution alters the diet composition of invertebrate consumers both in and beyond a noise-exposed grassland ecosystem

Anthropogenic noise is ubiquitous globally. However, we know little about how the impacts of noise alter fundamental ecosystem properties, such as resource consumption by invertebrate consumers. Using experimental noise manipulation and faecal DNA metabarcoding, we assessed how the direct and cross-trophic indirect effects of noise altered the dietary richness and specializations of omnivorous grasshoppers in a grassland ecosystem. We found that the experimental noise treatment expanded grasshoppers' dietary richness and resulted in dietary generalizations in both noise-exposed and adjacent relatively quieter areas. Unexpectedly, however, these dietary changes were primarily explained by the direct effect of noise not only in the noise-exposed areas but also in the adjacent quieter areas and were relaxed by indirect effects of noise such as reduced birds and predation risk and increased grasshoppers. Our work suggests that noise pollution can be key in explaining the variation of invertebrate consumers' diets across a gradient of noise-exposed environments.

How chronic anthropogenic noise can affect wildlife communities

Anthropogenic noise is a major pollutant in terrestrial and aquatic ecosystems. Since the industrial revolution, human activities have become increasingly noisy, leading to both acute and chronic disturbance of a wide variety of animals. Chronic noise exposure can affect animals over their lifespan, leading to changes in species interactions and likely altering communities. However, the community-level impacts of chronic noise are not well-understood, which impairs our ability for effective mitigation. In this review, we address the effects of chronic noise exposure on communities and explore possible mechanisms underlying these effects. The limited studies on this topic suggest that noise can affect communities by changing the behavior and/or physiology of species in a community, which results in direct or knock-on consequences for other species in the ecosystem. Major knowledge gaps remain due to the logistically complex and financially expensive nature of the long-term studies needed to address these questions. By identifying these gaps and suggesting approaches to answer them, we provide a road map toward mitigating the effects of a noisy world.

Long-term effects of noise pollution on the avian dawn chorus: a natural experiment facilitated by the closure of an international airport

The impacts of noise pollution on birdsong have been extensively investigated but potential long-term effects are neglected. Near airports, where noise levels are particularly high, birds start singing earlier in the morning, probably to gain more time of uninterrupted singing before air traffic sets in. In a previous study, we documented this phenomenon in the vicinity of Berlin Tegel airport. In 2020, Tegel airport closed down, giving us the opportunity to investigate potential long-term effects after noise removal and to gain insight into the mechanisms underlying the advancement of dawn singing. We found that several species at the airport shifted their song onset back after the closure and now had similar schedules to their conspecifics at a control site. Some species, however, still sang earlier near the closed airport. While the first suggests plastic adaptation, the latter suggests selection for early singing males in areas with long-lasting noise pollution. Our findings indicate that a uniform behavioural response to anthropogenic change in a community can be based on diverging evolutionary mechanisms. Overall, we show that noise pollution can have long-lasting effects on animal behaviour and noise removal may not lead to immediate recovery in some species.

Limiting motorboat noise on coral reefs boosts fish reproductive success

Anthropogenic noise impacts are pervasive across taxa, ecosystems and the world. Here, we experimentally test the hypothesis that protecting vulnerable habitats from noise pollution can improve animal reproductive success. Using a season-long field manipulation with an established model system on the Great Barrier Reef, we demonstrate that limiting motorboat activity on reefs leads to the survival of more fish offspring compared to reefs experiencing busy motorboat traffic. A complementary laboratory experiment isolated the importance of noise and, in combination with the field study, showed that the enhanced reproductive success on protected reefs is likely due to improvements in parental care and offspring length. Our results suggest noise mitigation could have benefits that carry through to the population-level by increasing adult reproductive output and offspring growth, thus helping to protect coral reefs from human impacts and presenting a valuable opportunity for enhancing ecosystem resilience.