Linking Massachusetts soundscapes to landscapes

" A great silence is spreading over the natural world even as the sound of man is becoming deafening. Little by little the vast orchestra of life, the chorus of the natural world, is in the process of being quietened. There has been a massive decrease in the density and diversity of key vocal creatures, both large and small. If you listen to a damaged soundscape … the community [of life] has been altered, and organisms have been destroyed, lost their habitat or been left to re-establish their places in the spectrum. As a result, some voices are gone entirely, while others aggressively compete to establish a new place in the increasingly disjointed chorus." Bernie Krause - The Great Animal Orchestra.

Massachusetts

Massachusetts is the most densely populated state in New England (864.8 people per square mile). After extensive deforestation, that peaked in the mid-nineteenth century, secondary forest cover gained back its dominance in Massachusetts (Hall et al., 2002), covering approximately 60% of the state (Rogan et al., 2016). Today, fragmentation of temperate forests in the region is primarily related to forest loss and degradation due to urban and suburban expansion, and commercial development (Rogan et al., 2016). Deforestation for the establishment of solar fields is also growing rapidly in the area (Ricci et al. 2020). 

Land change and the biodiversity crisis

The Earth is facing a biodiversity crisis, with an estimated 11,000- 58,000 species lost per year (Dirzo et al., 2014). Human-induced landscape changes, especially deforestation and forest fragmentation, are the main cause of biodiversity extinctions worldwide (Brondizio et al., 2019; Sala et al., 2000). Deforestation impacts biodiversity by modifying the size and configuration of habitat patches, the amount of edge habitat, and decreasing forest connectivity

Urbanization effects on birds:

Traffic

By 2030, sixty percent of the global population will live in urban areas (Seto, Güneralp, & Hutyra, 2012). Increased traffic from urbanization traffic can harm biodiversity by increasing noise intrusion into natural environments and contributing to a sound masking effect, where species communication is covered up by traffic noise, decreasing breeding success and the avoidance of predators (Barber, Crooks, & Fristrup, 2010).

Artificial Illumination

With urbanization, the amount of artificial illumination at night increases due to street, security, domestic, and vehicle lighting, resulting in an environment much brighter than natural moonlight conditions. This change in illumination affects the circadian rhythm of species (Aulsebrook et al., 2020; Bradshaw & Holzapfel, 2007) and disorients and disrupts the behavior of migrating birds (La Sorte, Fink, Buler, Farnsworth, & Cabrera-Cruz, 2017; Poot et al., 2008). The increase in lights is also related to an advanced onset and dawn activity in songbirds (Da Silva, Samplonius, Schlicht, Valcu, & Kempenaers, 2014) and extended foraging (Dwyer, Bearhop, Campbell, & Bryant, 2013). 

Human Edges

Suburban areas increase anthropogenic edges, increasing predation and decreasing reproductive outputs of interior forest species (Bocz et al., 2017; Valentine, Apol, & Proppe, 2019). Connectivity is known to promote abundance and decrease the extinction risk of species (Brooker, Brooker, & Cale, 1999; Haas, 1995; Martensen, Ribeiro, Banks-Leite, Prado, & Metzger, 2012), including birds  (Kang, Minor, Park, & Lee, 2015).

Ecoacoustics to monitor landscape change

Soundscape ecology is the study of the relationship between acoustics and the environment, characterizing soundscapes as the collection of biological, geophysical and human sounds within a landscape (Buxton et al., 2018; Pijanowski et al., 2011). Acoustic community diversity is defined as the aggregation of all species that produce sounds at a particular location and time (Farina & James, 2016; Sueur et al., 2014). Each community has a distinctive acoustic signature that depends on the species composition (Farina & Pieretti, 2014). The aggregation of all these signatures will result in a specific community signature. Acoustic community diversity correlates well with biodiversity, and can represent habitat health (Tucker et al., 2014).

A soundscape can be characterized by biophony (sounds of the biota), geophony (like rain, or wind), and anthrophony (human-made sounds). The acoustic space in natural soundscapes is mostly occupied by biophony, although anthrophony can also be present. The urban acoustic space on the other extreme is mostly occupied by anthrophony, while rural landscapes have a combination of all three soundscape components. Species diversity is expected to decrease in more anthropogenic-based soundscapes.

Sampling Summer 2019

During the summer of 2019, we sampled 11 sites on a 5-15 minutes on-off schedule.

For this initial stage of the study we selected the Mass Audubon sites: Lake Wampanoag, Flat Rocks, Rutland Brook, Wachusett Meadow, Lincoln Woods, Cooks Canyon, Eagle Lake, Burncoat Pond, Broad Meadow Brook, and Pierpoint Meadow. We also included the Leadmine mountain open space area in Sturbridge, MA.

Sites were selected to include a diversity of landscapes, including forested areas within urban, suburban, and rural landscapes.

Summary of results

Core habitat is defined by a contiguous natural land cover of at least 100 acres and 200 meters wide; areas not fulfilling this condition are classified as non-core. Large patches of natural habitat, classified as "better core habitat" presented higher acoustic diversity than small (less than 100 ha) patches, which are classified as "no core". Moreover, no-core patches presented higher anthropogenic sounds.

a) ACI, b) NDSI, c) Anthrophony, d) Biophony. Markers tagged with the same letter are not significantly different (Kruskal–Wallis followed by Dunn’s test, α = 0.05)

The permeability of the matrix to movement plays a vital role in defining the impact of fragmentation on biodiversity. We found that highly connected forest patches favored acoustic diversity. Given the nature of the landscape, connectivity in our study area acts by decreasing the effects of human pressure.

The presence of increased live cover measured as NDVI was associated with an increase of sounds from biota (biophony) and a decrease of human-dominated sounds (anthrophony). Our results showing a decrease in anthrophony with increased percent forest cover shows that forests act as sound buffers attenuating traffic noise.

Urbanization creates human edges and a matrix of high pressure, including increased traffic noise and artificial illumination. The decrease in biophony and ACI associated with human edges are more possibly related to increased traffic and human noise associated with edges.

We identified a negative impact of artificial light on acoustic complexity. This can be due to the combined effects of traffic noise and increased photoperiod on stress.

This study shows the potential of ecoacoustics for monitoring habitat quality in human-dominated landscapes. The characteristic scales found in this study indicate that urban design should consider potential impacts acting at scales beyond sites, and that conservation planning should focus on managing the context matrix. Our work identifies the scale and the matrix characteristics to be managed to support bioacoustic diversity, including noise, artificial illumination pollution, anthropogenic edge, and forest connectivity.

Our study found significant correlations between acoustic diversity and human pressure variables within a radius of 1.5 to 3 km from the sampling site, indicating that acoustic metrics can act as robust landscape-scale indicators that can inform planning practices to support biodiversity in urbanized landscapes.

a) ACI, b) NDSI, c) Anthrophony, d) Biophony. Markers tagged with the same letter are not significantly different (Kruskal–Wallis followed by Dunn’s test, α = 0.05)