There is a companion article exploring the issue from the perspective of environmental monitoring over at ArkFab.

Human influence on the environment has increased dramatically over the last 10,000 years, to the point that some geologists have argued that human reworking of the earth defines a new geologic age, The Anthropocene. (Zalasiewicz et al, 2008) Much of the focus has been on relatively robust, tangible changes in biogeochemistry. Examples include:

  • megafaunal extinction, accelerated erosion (Zalasiewicz et al, 2008) and nitrogen fixation resulting from the spread of intensive subsistence patterns
  • the loss of stratospheric ozone resulting from the release of novel chlorofluorocarbons

However, fleeting and less tangible effects are also important. Two examples are:

  • the light pollution resulting from urbanization and transportation infrastructure
  • changes in the acoustic environment resulting from direct addition of sonic energy and memes, as well as indirect sources.

A year-long composite view of the earth at night, showing human light generation. White lights are cities; blue lights are fishing boats; green lights are natural gas flares, and red lights are ‘ephemeral light sources’, interpreted as fires. Image from  NOAA National Geophysical Data Center – click for source + discussion.

Light pollution, the scourge of urban astronomers, is a well-accepted phenomenon with serious consequences. A 2004 review begins:

In the past century, the extent and intensity of artificial night lighting has increased such that it has substantial effects on the biology and ecology of species in the wild. We distinguish “astronomical light pollution”, which obscures the view of the night sky, from “ecological light pollution”, which alters natural light regimes in terrestrial and aquatic ecosystems. Some of the catastrophic consequences of light for certain taxonomic groups are well known, such as the deaths of migratory birds around tall lighted structures, and those of hatchling sea turtles disoriented by lights on their natal beaches. The more subtle influences of artificial night lighting on the behavior and community ecology of species are less well recognized, and constitute a new focus for research in ecology and a pressing conservation challenge. (Longcore & Rich 2004)

The amount of sonic energy released by human activity is recognized as an urban nuisance as well as an occupational safety concern. It also has recognized ecological effects: urban European robins have begun singing at night, when they have less acoustic competition. (Fuller et al 2007) Frogs have begun changing the pitch of their croaks in order to talk over traffic noise (Paris et al 2009)  In addition to sonic energy, human activity has released sonic memes into the environment. A meme is a self-replicating information pattern; jokes and computer viruses are two examples of memes. A person or computer acquires a meme and then spreads it, through retelling or infected emails. Sonic memes, such as ambulance sirens and cellphone ringtones, have been picked and repeated by songbirds. (Stover 2009) This is very interesting: human memes, the basis of Richard Dawkins’ ‘extended phenotype’ concept, have organically extended into other animals’ extended phenotype. (Recent reports of dolphins mimicking human speech are also very interesting in this context. The reverse flow also occurs, as animal communications are repackaged as ringtones or ambient music.)

It’s perhaps no surprise that our ships and sonar have made the oceans alarmingly loud, but human activity has influenced the acoustic environment in indirect, often surprising ways. Anthropogenic carbon emissions are drastically changing ocean chemistry: the oceans have become more acidic with an average decrease of 0.1 pH since the industrial revolution (IPCC AR4 2007 WGII Ch.1). pH is a logarithmic measure of acidity, so a pH change of 0.1 is a 125% increase in hydrogen ion concentration. In addition to the effects on corals and other organisms which depend on a more basic ocean, researchers at the Monterey Bay Aquarium have made a surprising prediction: acidification may make the oceans louder in certain frequency ranges. (Hester et al. 2008) At the same time, changes in climate have resulted in catastrophic outbreaks of bark beetle. Researchers at the Santa Fe Institute have argued for a sonic component to these outbreaks, in which bark beetles home in on acoustic signals released by trees stressed by dehydration. (Dunn & Crutchfield, 2006)

What is the sound of one beetle chirping? It has a spectrogram like this one from the Acoustic Ecology Institute – click on the image for more spectrograms and recordings!

Considering the scale and significance of human influence on the sonic and optic environments, there is a great deal we could learn from widespread ecological monitoring of sound and light. The review cited earlier reccomends: “measurements of light disturbance should be included routinely as part of enviromental monitoring protocols“. (Longcore & Rich 2004) In the oceans, tools like NOAA’s autonomous hydrophone array have uncovered a great variety of information, including some rather Lovecraftian anomalies, with names like Bloop, Julia, Train, and Slow Down. In spite of these monitoring efforts, the Acoustic Ecology Institute’s David Dunn recently reported that “very little is known about the extent of anthropogenic noise in the sea, or the effects of such noise on ocean species.

Here's a

Here’s a module’s eye view of an environmental monitor for sound and light pollution. I’d like to see a distributed array of these, keeping tabs on he photons and sound waves around us.

On land, monitoring of sonic ecology has thusfar been fairly transient and concentrated on localized and/or urban settings (eg, Alicia-Pou et al2005; Maisonneuve et al 2006). In order to build a better database of the sonic landscape, I would envision a semi-autonomous terraphone array, mimicking NOAA’s aquatic model. This array might be produced and maintained by citizen scientists, an implementation I discuss in more detail at ArkFab. Beyond anthropogenic sound and light pollution, the dataset from this monitoring program could be useful in other ways. For example, a record of animal sounds could directly give information about their populations in a given region; indirectly, it could be used to infer information about populations of their predators, prey, and symbiotes. Over time, this data could be used to understand migration patterns and ecological succession. Widespread light measurements may provide insight to a phenomenon called global dimming. Global dimming is the effect of airborn particles (such as pollution) to reduce the amount of sunlight reaching the surface, by reflecting it directly or by spawning reflective clouds. Some studies have indicated that the dimming has recently begun to decrease, while other studies disagree. Widespread light-level monitoring might help address open questions about the climatic effects of clouds, as well as provide information for trying to understand the effects of global dimming and brightening on local ecosystems.

“The future is so bright, I gotta wear shades.”

José Alicea-Pou, Olga Viñas-Curiel, Wanda Cruz-Vizcarrondo, & Osvaldo Alomar (2005). Monitoring of the Environmental Noise Level in San Juan, Puerto Rico Environmental Quality Board

David Dunn, & James P. Crutchfield (2006). Insects, Trees, and Climate: The Bioacoustic Ecology of Deforestation
and Entomogenic Climate Change Santa Fe Institute Working Paper arXiv: q-bio/0612019v1

Fuller, R., Warren, P., & Gaston, K. (2007). Daytime noise predicts nocturnal singing in urban robins Biology Letters, 3 (4), 368-370 DOI: 10.1098/rsbl.2007.0134
Hester, K., Peltzer, E., Kirkwood, W., & Brewer, P. (2008). Unanticipated consequences of ocean acidification: A noisier ocean at lower pH Geophysical Research Letters, 35 (19) DOI: 10.1029/2008GL034913

Longcore, T., & Rich, C. (2004). Ecological Light Pollution Frontiers in Ecology and the Environment, 2 (4) DOI: 10.2307/3868314

Nicolas Maisonneuve, Matthias Stevens, Maria E. Niessen, Peter Hanappe, & Luc Steels (2009). Citizen Noise Pollution Monitoring The Proceedings of the 10th International Digital Government Research Conference

Kirsten M. Parris, Meah Velik-Lord, & Joanne M. A. North (2009). Landscape Function
Frogs Call at a Higher Pitch in Traffic Noise
Ecology and Society, 14 (1)

Rosenzweig, C., G. Casassa, D.J. Karoly, A. Imeson, C. Liu, A. Menzel, S. Rawlins, T.L. Root, B. Seguin, & P. Tryjanowski (2007). Assessment of observed changes and responses in natural and managed systems. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change

Dawn Stover (2009). Not So Silent Spring Conservation Magazine, 10 (1)

Zalasiewicz, J., Williams, M., Smith, A., Barry, T., Coe, A., Bown, P., Brenchley, P., Cantrill, D., Gale, A., Gibbard, P., Gregory, F., Hounslow, M., Kerr, A., Pearson, P., Knox, R., Powell, J., Waters, C., Marshall, J., Oates, M., Rawson, P., & Stone, P. (2008). Are we now living in the Anthropocene GSA Today, 18 (2) DOI: 10.1130/GSAT01802A.1